01528nas a2200493 4500008004100000245009100041210006900132300001400201490000600215100002600221700002600247700002000273700002000293700002500313700002900338700001600367700002600383700001800409700002000427700002500447700002400472700002700496700002900523700002000552700002100572700001800593700002900611700002500640700001700665700001800682700002600700700002500726700002700751700003000778700001900808700003000827700001800857700003200875700002300907700001800930700001600948700001500964856005500979 2024 eng d00aBiogeochemical and community ecology responses to the wetting of non-perennial streams0 aBiogeochemical and community ecology responses to the wetting of a815 - 8260 v21 aPrice, Adam, Nicholas1 aZimmer, Margaret, Ann1 aBergstrom, Anna1 aBurgin, Amy, Jo1 aSeybold, Erin, Cedar1 aKrabbenhoft, Corey, Anne1 aZipper, Sam1 aBusch, Michelle, Hope1 aDodds, W., K.1 aWalters, Annika1 aRogosch, Jane, Sarah1 aStubbington, Rachel1 aWalker, Richard, Harry1 aStegen, James, Christian1 aDatry, Thibault1 aMessager, Mathis1 aOlden, Julian1 aGodsey, Sarah, Elizabeth1 aShanafield, Margaret1 aLytle, David1 aBurrows, Ryan1 aKaiser, Kendra, Elena1 aAllen, George, Henry1 aMims, Meryl, Christine1 aTonkin, Jonathan, Douglas1 aBogan, Michael1 aHammond, John, Christophe1 aBoersma, Kate1 aMyers-Pigg, Allison, Nicole1 aDelVecchia, Amanda1 aAllen, Daniel1 aYu, Songyan1 aWard, Adam uhttps://www.nature.com/articles/s44221-024-00298-300421nas a2200097 4500008004100000245009200041210006900133300001200202100001800214856009100232 2024 eng d00aScientific collaborative within-group conduct, data-sharing, and publication agreements0 aScientific collaborative withingroup conduct datasharing and pub abiae0731 aDodds, W., K. uhttps://academic.oup.com/bioscience/advance-article/doi/10.1093/biosci/biae073/775652100987nas a2200313 4500008004100000245009900041210006900140300001200209490000600221100002200227700002000249700001800269700002000287700001600307700002200323700001800345700002500363700002500388700002000413700002300433700002500456700002200481700001500503700001600518700002300534700001900557700002400576856007300600 2023 eng d00aHow low can you go? Widespread challenges in measuring low stream discharge and a path forward0 aHow low can you go Widespread challenges in measuring low stream a804-8110 v81 aSeybold, Erin, C.1 aBergstrom, Anna1 aJones, Nathan1 aBurgin, Amy, J.1 aZipper, Sam1 aGodsey, Sarah, E.1 aDodds, W., K.1 aZimmer, Margaret, A.1 aShanafield, Margaret1 aDatry, Thibault1 aMazor, Raphael, D.1 aMessager, Mathis, L.1 aOlden, Julian, D.1 aWard, Adam1 aYu, Songyan1 aKaiser, Kendra, E.1 aShogren, Arial1 aWalker, Richard, H. uhttps://aslopubs.onlinelibrary.wiley.com/doi/full/10.1002/lol2.1035600606nas a2200181 4500008004100000245009400041210006900135300001200204490000700216100002100223700002300244700001900267700001800286700001900304700001800323700001800341856006500359 2023 eng d00aImpacts of riparian and non-riparian woody encroachment on tallgrass prairie ecohydrology0 aImpacts of riparian and nonriparian woody encroachment on tallgr a290-3010 v261 aKeen, Rachel, M.1 aNippert, Jesse, B.1 aSullivan, P.L.1 aRatajczak, Z.1 aRitchey, Brynn1 aO’Keefe, K.1 aDodds, W., K. uhttps://link.springer.com/article/10.1007/s10021-022-00756-700659nas a2200193 4500008004100000245011800041210006900159300001000228490000700238100002200245700001800267700002100285700001800306700002400324700001900348700002400367700001700391856005700408 2023 eng d00aTrajectories and state changes of a grassland stream and riparian zone after a decade of woody vegetation removal0 aTrajectories and state changes of a grassland stream and riparia ae28300 v331 aDodds, Walter, K.1 aRatajczak, Z.1 aKeen, Rachel, M.1 aNippert, J.B.1 aGrudzinski, Bartosz1 aVeach, Allison1 aTaylor, Jeffery, H.1 aKuhl, Amanda uhttps://onlinelibrary.wiley.com/doi/10.1002/eap.283000591nas a2200157 4500008004100000245014300041210006900184300001400253490000700267100001800274700002200292700002300314700002400337700001800361856005400379 2022 eng d00aAssessing transport and retention of nitrate and other materials through the riparian zone and stream channel with simulated precipitation0 aAssessing transport and retention of nitrate and other materials a757 - 7660 v131 aDodds, W., K.1 aWichman, Gretchen1 aGuinnip, James, P.1 aCorman, Jessica, R.1 aBlair, J., M. uhttps://onlinelibrary.wiley.com/toc/2041210x/13/300605nas a2200169 4500008004100000245012600041210006900167300001400236490000700250100002400257700001600281700002000297700001900317700002300336700001800359856005800377 2022 eng d00aPrairie stream metabolism recovery varies based on antecedent hydrology across a stream network after a bank‐full flood0 aPrairie stream metabolism recovery varies based on antecedent hy a1986-19990 v671 aRuffing, Claire, M.1 aVeach, A.M.1 aSchechner, Anne1 aRüegg, Janine1 aTrentman, Matt, T.1 aDodds, W., K. uhttps://onlinelibrary.wiley.com/doi/10.1002/lno.1218202250nas a2200349 4500008004100000245011000041210006900151300001400220490000700234520126000241100001801501700001701519700001601536700001601552700001501568700001701583700001601600700002001616700001601636700001801652700001501670700001701685700001601702700001601718700001901734700001801753700001701771700001601788700001401804700001701818856006501835 2020 eng d00aConnections and feedback: Aquatic, plant, and soil microbiomes in heterogeneous and changing environments0 aConnections and feedback Aquatic plant and soil microbiomes in h a548 - 5620 v703 a

Plant, soil, and aquatic microbiomes interact, but scientists often study them independently. Integrating knowledge across these traditionally separate subdisciplines will generate better understanding of microbial ecological properties. Interactions among plant, soil, and aquatic microbiomes, as well as anthropogenic factors, influence important ecosystem processes, including greenhouse gas fluxes, crop production, nonnative species control, and nutrient flux from terrestrial to aquatic habitats. Terrestrial microbiomes influence nutrient retention and particle movement, thereby influencing the composition and functioning of aquatic microbiomes, which, themselves, govern water quality, and the potential for harmful algal blooms. Understanding how microbiomes drive links among terrestrial (plant and soil) and aquatic habitats will inform management decisions influencing ecosystem services. In the present article, we synthesize knowledge of microbiomes from traditionally disparate fields and how they mediate connections across physically separated systems. We identify knowledge gaps currently limiting our abilities to actualize microbiome management approaches for addressing environmental problems and optimize ecosystem services.

1 aDodds, W., K.1 aZeglin, L.H.1 aRamos, R.J.1 aPlatt, T.G.1 aPandey, A.1 aMichaels, T.1 aMasigol, M.1 aKlompen, A.M.L.1 aKelly, M.C.1 aJumpponen, A.1 aHauser, E.1 aHansen, P.M.1 aGreer, M.J.1 aFattahi, N.1 aDelavaux, C.S.1 aConnell, R.K.1 aBillings, S.1 aBever, J.D.1 aBarua, N.1 aAgusto, F.B. uhttps://academic.oup.com/bioscience/article/70/7/548/582695802059nas a2200145 4500008004100000245007900041210006900120300001400189490000700203520159600210100001901806700001401825700001801839856005601857 2020 eng d00aDoes riparian fencing protect stream water quality in cattle-grazed lands?0 aDoes riparian fencing protect stream water quality in cattlegraz a121 - 1350 v663 a

Cattle degrade streams by increasing sediment, nutrient, and fecal bacteria levels. Riparian fencing is one best management practice that may protect water quality within many grazed lands. Here we surveyed the literature and summarized the responses of sediment, nutrient, and fecal indicator bacteria levels to riparian exclosure fencing in cattle-grazed lands. Overall, our review of relevant literature supports the role of riparian exclosure fencing in reducing the negative impact of cattle on water quality, particularly for sediment and fecal indicator bacteria in temperate forest and temperate grassland streams. Establishing buffer widths > 5–10 m appears to increase the likelihood of water quality improvements. Fencing may also be effective at reducing pollutant inputs during stormflows. Our survey also identified critical spatial and thematic gaps that future research programs should address. Despite cattle grazing being prevalent in 12 terrestrial biomes, our systematic search of the empirical literature identified 26 relevant studies across only three biomes. Regions with the greatest cattle populations remain largely unstudied. In addition, we identified inconsistencies in how studies reported information on regional factors, cattle management, and other metrics related to study results. We provide a list of standard parameters for future studies to consider reporting to improve cross-study comparisons of riparian fencing impacts. We also encourage future studies in semi-arid and tropical regions where cattle grazing is common.

1 aGrudzinski, B.1 aFritz, K.1 aDodds, W., K. uhttp://link.springer.com/10.1007/s00267-020-01297-203217nas a2200289 4500008004100000022001400041245008400055210007100139300001000210490000800220520230400228100002102532700002102553700001802574700003102592700002402623700002002647700001802667700002202685700002702707700002002734700002602754700002702780700002202807700001802829856008002847 2020 eng d a0022-047700aPlant phylogenetic history explains in‐stream decomposition at a global scale0 aPlant phylogenetic history explains in‐stream decomposition at a a17-350 v1083 a

    1. Evolutionary history and adaptation to climate shape plant traits. Some include leaf traits that influence litter quality. Thus, evolutionary history should affect litter decomposition, a crucial ecosystem process. In addition, litter decomposition is directly influenced by climate. We consequently expect plant phylogeny, adaptation and climate to jointly influence litter decomposition. These effects and their interactions have yet to be untangled at a global scale.
    2. Here we present an analysis of variation in litter decomposition rates in rivers and streams across 285 published studies for 239 species (from ferns to angiosperms) distributed at 494 locations world-wide. We estimated the relative contributions of climatic conditions and phylogenetic heritage on litter decomposition rates, partitioning phylogenetic from climatic effects at the site and species levels using phylogenetic eigenvector analysis and phylogenetic linear mixed models. In addition, we modelled transitions in decomposition rates under a suite of multiple adaptive-regime Ornstein–Uhlenbeck models to test the hypothesis that natural selection has shaped clade-level litter decomposition rates.
    3. Leaf litter decomposition rate exhibited a significant phylogenetic signal. Modelling decomposition rate as a function of location, climatic niche and phylogeny consistently recovered phylogeny alone as one of the top models in species‐level analyses. Since many previous studies have focused on the same species across many locations, we also conducted analyses at the species × site level. Both phylogenetic and climatic factors were favoured in models of this analysis, but the single most important predictor for angiosperms and for all taxa analysed together was phylogeny alone.
    4. Synthesis. For plant species distributed globally at nearly 500 locations we found that plant phylogenetic history is a critically important predictor of litter decomposition rate in rivers and streams, explaining more of the variance in decomposition than site or climatic regime. Thus, our study demonstrates the influence of evolutionary history on suites of plant traits that shape a key ecosystem process.

1 aLeRoy, Carri, J.1 aHipp, Andrew, L.1 aLueders, Kate1 aShah, Jennifer, J. Follsta1 aKominoski, John, S.1 aArdón, Marcelo1 aDodds, W., K.1 aGessner, Mark, O.1 aGriffiths, Natalie, A.1 aLecerf, Antoine1 aManning, David, W. P.1 aSinsabaugh, Robert, L.1 aWebster, Jack, R.1 aWardle, David uhttps://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2745.1326202241nas a2200157 4500008004100000245014300041210006900184490000700253520168100260100001901941700001801960700001701978700001501995700001802010856005502028 2020 eng d00aUsing path analysis to determine interacting effects of biotic and abiotic factors on patch-scale biogeochemical rates in a prairie stream0 aUsing path analysis to determine interacting effects of biotic a0 v823 a

Biogeochemical rates within streams vary with ecosystem properties including the distribution of fishes. While many studies investigate the singular effect of fishes on ecosystem components, there is a limited understanding of how fish presence interacts with other ecosystem properties to affect ecosystem structure and function. Here, we used path analyses to elucidate direct and indirect effects of fish presence, and other ecosystem properties on ecosystem respiration (ER), gross primary production (GPP), and ammonium uptake. Experimental responses of fish removal on patch scale (300 cm2) benthic rates of ER, GPP, and ammonium uptake were measured at two sites in a prairie stream. The effect of fish was determined by comparing substrata from field exclosures with fish absent to substrata exposed to fish. Total path model-explained variance was greatest for ER (R2 = 0.55) and least for ammonium uptake (R2 = 0.36) and GPP (R2 = 0.34). Fish decreased algal biomass and directly increased all biogeochemical rates. The relative importance of the different abiotic ecosystem properties varied by process; however, FBOM and substrata size were important for most rates. This study provides evidence for predominantly direct effects of fish on both stream structure and function in a prairie stream. Our results emphasize that interactions between biotic and abiotic factors should be considered when determining drivers of biogeochemical activity. We suggest that simple linear food webs that consist of top–down or bottom–up control are not always sufficient to describe animal effects on ecosystem rates.

1 aTrentman, M.T.1 aDodds, W., K.1 aGido, K., B.1 aRüegg, J.1 aRuffing, C.M. uhttp://link.springer.com/10.1007/s00027-020-0702-803304nas a2200217 4500008004100000245012500041210006900166300001100235490000700246520259200253100001802845700002902863700001902892700002002911700001902931700002202950700002102972700001702993700002203010856005403032 2019 eng d00aThe freshwater biome gradient framework: predicting macroscale properties based on latitude, altitude, and precipitation0 afreshwater biome gradient framework predicting macroscale proper ae027860 v103 a

Understanding global ecological patterns and processes, from biogeochemical to biogeographical, requires broad‐scale macrosystems context for comparing and contrasting ecosystems. Climate gradients (precipitation and temperature) and other continental‐scale patterns shape freshwater environments due to their influences on terrestrial environments and their direct and indirect effects on the abiotic and biotic characteristics of lakes, streams, and wetlands. We combined literature review, analyses of open access data, and logical argument to assess abiotic and biotic characters of freshwater systems across gradients of latitude and elevation that drive precipitation, temperature, and other variability. We explored the predictive value of analyzing patterns in freshwater ecosystems at the global macrosystems scale. We found many patterns based on climate, particularly those dependent upon hydrologic characteristics and linked to characteristics of terrestrial biomes. For example, continental waters of dry areas will generally be widely dispersed and have higher probability of drying and network disconnection, greater temperatures, greater inorganic turbidity, greater salinity, and lower riparian canopy cover relative to areas with high precipitation. These factors will influence local community composition and ecosystem rates. Enough studies are now available at the continental or global scale to start to characterize patterns under a coherent conceptual framework, though considerable gaps exist in the tropics and less developed regions. We present illustrative global‐scale trends of abiotic, biotic, and anthropogenic impacts in freshwater ecosystems across gradients of precipitation and temperature to further understanding of broad‐scale trends and to aid prediction in the face of global change. We view freshwater systems as occurring across arrays of multiple gradients (including latitude, altitude, and precipitation) rather than areas with specific boundaries. While terrestrial biomes capture some variability along these gradients that influence freshwaters, other features such as, slope, geology, and historical glaciation also influence freshwaters. Our conceptual framework is not so much a single hypothesis as a way to logically characterize patterns in freshwaters at scales relevant to (1) evolutionary processes that give rise to freshwater biodiversity, (2) regulatory units that influence freshwater ecosystems, and (3) the current scope of anthropogenic impacts on freshwaters and the vital ecosystem services they provide.

1 aDodds, W., K.1 aBruckerhoff, Lindsey, A.1 aBatzer, Darold1 aSchechner, Anne1 aPennock, Casey1 aRenner, Elizabeth1 aTromboni, Flavia1 aBigham, Kari1 aGrieger, Samantha uhttps://onlinelibrary.wiley.com/toc/21508925/10/701657nam a2200169 4500008004100000020001800041022001800059245007700077210006900154250000600223260001300229300000800242520112400250100001801374700001701392856007801409 2019 eng d a9780128132562 a978012813255500aFreshwater ecology: concepts and environmental applications of limnology0 aFreshwater ecology concepts and environmental applications of li a3 bElsevier a9983 a

Description: Freshwater Ecology, Third Edition, covers everything from the basic chemical and physical properties of water, to the advanced and unifying concepts of community ecology and ecosystem relationships found in continental waters. Giving students a solid foundation for both courses and future fieldwork, and updated to include key issues, including how to balance ecological and human health needs, GMOs, molecular tools, fracking, and a host of other environmental issues, this book is an ideal resource for both students and practitioners in ecology and related fields.
Key Features: 1. Provides an updated revision of this classic text, covering both basic scientific concepts and environmental applications.
2. Includes additional biography boxes with greater cultural diversity of the featured scientists
3. Covers expanded content on developing nations, ecosystem goods and services, properties of water, global change, impacts of fracking, molecular tools for classification and identification of aquatic organisms, a discussion of emergent diseases and aquatic habitats, and more

1 aDodds, W., K.1 aWhiles, M.R. uhttps://www.elsevier.com/books/freshwater-ecology/dodds/978-0-12-813255-503030nas a2200229 4500008004100000245012900041210006900170300001100239490000800250520230600258653001802564653003102582653001002613653002302623100001902646700001602665700002302681700001102704700001702715700001802732856005002750 2019 eng d00aHow landscape heterogeneity governs stream water concentration-discharge behavior in carbonate terrains (Konza Prairie, USA)0 aHow landscape heterogeneity governs stream water concentrationdi a1189890 v5273 a

Mounting evidence suggests ecosystem changes that alter subsurface water fluxes and carbon dioxide concentrations in carbonate terrains may drive measurable changes in chemical weathering rates, stream water chemistry, and flow path evolution on human timescales. We test this idea by exploring if the encroachment of woody vegetation into grasslands in a carbonate terrain landscape at the Konza Prairie (KS, USA) has resulted in differences in landscape-stream connectivity and, thus, the behavior of stream water solutes. Woody encroachment (up to 60% cover) at Konza has been observed on watersheds, particularly those that experience a fire return interval of four years or greater. We focus on three headwater catchments (two grassland and one woody-encroached) and a downstream confluence, and analyze stream water discharge and chemistry (major anions, cations, and dissolved nutrients) measured from 2015 to 2016.

We observe that the woody-encroached watershed exhibits a greater area-normalized solute flux and greater degree of chemodynamic behavior for most geogenic species compared to the less encroached grassland watersheds. The downstream confluence exhibits the most chemostatic behavior for these same solutes compared to the low order watersheds. We interpret the chemodynamic behavior of the woody-encroached watersheds to arise from a greater diversity of flow paths and solute sources that contribute to this stream. End member mixing analysis (EMMA) supports this hypothesis but also indicates a possible “missing” end member which we interpret to be solutes likely derived from clay weathering along limestone-mudstone boundaries. We invoke differences in rooting systems between grass and woody species to explain the differences in flow paths and solute generation between these headwater sites given that they sit adjacent to each other, dissect the same nearly horizontal (dip 0.1–0.21°NW) lithologic units, and experience the same climate. If these processes hold true at other sites, then the globally observed encroachment of woody vegetation into grasslands may deepen flow paths and enhance chemical weathering fluxes from ecosystems, and over long-time periods alter the trajectory of soil development and landscape evolution.

10aCritical zone10aEnd member mixing analysis10aKarst10awoody encroachment1 aSullivan, P.L.1 aStops, M.W.1 aMacpherson, G., L.1 aLi, L.1 aHirmas, D.R.1 aDodds, W., K. uhttps://doi.org/10.1016/j.chemgeo.2018.12.00202043nas a2200145 4500008004100000245009600041210006900137300001000206490000600216520154900222100002601771700002001797700001801817856006201835 2019 eng d00aNutrients, eutrophication and harmful algal blooms along the freshwater to marine continuum0 aNutrients eutrophication and harmful algal blooms along the fres ae13730 v63 a

Agricultural, urban and industrial activities have dramatically increased aquatic nitrogen and phosphorus pollution (eutrophication), threatening water quality and biotic integrity from headwater streams to coastal areas world‐wide. Eutrophication creates multiple problems, including hypoxic “dead zones” that reduce fish and shellfish production; harmful algal blooms that create taste and odor problems and threaten the safety of drinking water and aquatic food supplies; stimulation of greenhouse gas releases; and degradation of cultural and social values of these waters. Conservative estimates of annual costs of eutrophication have indicated $1 billion losses for European coastal waters and $2.4 billion for lakes and streams in the United States. Scientists have debated whether phosphorus, nitrogen, or both need to be reduced to control eutrophication along the freshwater to marine continuum, but many management agencies worldwide are increasingly opting for dual control. The unidirectional flow of water and nutrients through streams, rivers, lakes, estuaries and ultimately coastal oceans adds additional complexity, as each of these ecosystems may be limited by different factors. Consequently, the reduction of just one nutrient upstream to control eutrophication can allow the export of other nutrients downstream where they may stimulate algal production. The technology exists for controlling eutrophication, but many challenges remain for understanding and managing this global environmental problem.

1 aWurtsbaugh, Wayne, A.1 aPaerl, Hans, W.1 aDodds, W., K. uhttps://onlinelibrary.wiley.com/doi/abs/10.1002/wat2.137302369nas a2200241 4500008004100000245013000041210006900171300001200240490000700252520156900259653001601828653002401844653001901868653002001887653002001907653002801927653002301955653001801978100002401996700001802020700002302038856006602061 2019 eng d00aRemoval of woody riparian vegetation substantially altered a stream ecosystem in an otherwise undisturbed grassland watershed0 aRemoval of woody riparian vegetation substantially altered a str a64 - 760 v223 a

Riparian zones are key interfaces between stream and terrestrial ecosystems. Yet, we know of no whole-watershed experiments that cut only woody vegetation in the riparian zone in an otherwise intact watershed to isolate the role of riparian zones on stream ecology. We removed all of the woody riparian vegetation (from 10- and 30-m-wide buffers in headwaters and main channels, respectively) for 5 km of stream in a single watershed while leaving the remainder of the grassland watershed un-impacted. We assessed water chemistry changes 3 years before and 3 years after riparian wood removal and in two neighboring control watersheds with a before–after, control-impact design and analysis. Riparian woody removal caused 10–100-fold increases in mean stream water nitrate concentrations and pulses of high nitrate for 3 years thereafter. Other nutrients and total suspended solids increased 2–25 times for the 3 years of post-removal. In-stream rates of gross primary production, ecosystem respiration, and net ecosystem production had large treatment effect sizes but also high variance among samples. Past studies of whole-watershed deforestations showed similar water quality responses to our riparian deforestation. Riparian zones of grassland streams are sensitive to disturbance and likely impart relatively greater influence on stream structure and function than the upslope of the watershed. Our results further emphasize the role of riparian zones in biogeochemically linking aquatic and terrestrial habitats.

10adisturbance10aprairie restoration10aPrairie stream10ariparian buffer10awater chemistry10awhole-stream metabolism10awoody encroachment10awoody removal1 aLarson, Danelle, M.1 aDodds, W., K.1 aVeach, Allison, M. uhttps://link.springer.com/article/10.1007%2Fs10021-018-0252-202718nas a2200421 4500008004100000245009300041210006900134300001400203490000700217520145600224100001501680700001801695700001901713700001901732700002501751700001701776700002501793700002501818700002301843700002201866700002301888700002201911700001701933700002201950700002301972700002401995700002602019700002102045700002302066700002202089700002402111700002102135700002302156700001702179700002602196700002102222856005302243 2018 eng d00aContinental-scale decrease in net primary productivity in streams due to climate warming0 aContinentalscale decrease in net primary productivity in streams a415 - 4200 v113 a

Streams play a key role in the global carbon cycle. The balance between carbon intake through photosynthesis and carbon release via respiration influences carbon emissions from streams and depends on temperature. However, the lack of a comprehensive analysis of the temperature sensitivity of the metabolic balance in inland waters across latitudes and local climate conditions hinders an accurate projection of carbon emissions in a warmer future. Here, we use a model of diel dissolved oxygen dynamics, combined with high-frequency measurements of dissolved oxygen, light and temperature, to estimate the temperature sensitivities of gross primary production and ecosystem respiration in streams across six biomes, from the tropics to the arctic tundra. We find that the change in metabolic balance, that is, the ratio of gross primary production to ecosystem respiration, is a function of stream temperature and current metabolic balance. Applying this relationship to the global compilation of stream metabolism data, we find that a 1 °C increase in stream temperature leads to a convergence of metabolic balance and to a 23.6% overall decline in net ecosystem productivity across the streams studied. We suggest that if the relationship holds for similarly sized streams around the globe, the warming-induced shifts in metabolic balance will result in an increase of 0.0194 Pg carbon emitted from such streams every year.

1 aSong, Chao1 aDodds, W., K.1 aRüegg, Janine1 aArgerich, Alba1 aBaker, Christina, L.1 aBowden, W.B.1 aDouglas, Michael, M.1 aFarrell, Kaitlin, J.1 aFlinn, Michael, B.1 aGarcia, Erica, A.1 aHelton, Ashley, M.1 aHarms, Tamara, K.1 aJia, Shufang1 aJones, Jeremy, B.1 aKoenig, Lauren, E.1 aKominoski, John, S.1 aMcDowell, William, H.1 aMcMaster, Damien1 aParker, Samuel, P.1 aRosemond, Amy, D.1 aRuffing, Claire, M.1 aSheehan, Ken, R.1 aTrentman, Matt, T.1 aWhiles, M.R.1 aWollheim, Wilfred, M.1 aBallantyne, Ford uhttp://www.nature.com/articles/s41561-018-0125-500443nas a2200121 4500008004100000245006700041210006700108260004300175490001400218100001800232700001800250856005300268 2018 eng d00aDissolved organic carbon dynamics in tallgrass prairie streams0 aDissolved organic carbon dynamics in tallgrass prairie streams aManhattan, KSbKansas State University0 vMS Thesis1 aHiggs, Sophie1 aDodds, W., K. uhttp://krex.k-state.edu/dspace/handle/2097/3915306735nas a2200373 4500008004100000245012300041210006900164300000800233490000700241520565500248100001505903700001405918700001305932700002105945700002005966700001805986700001706004700001906021700001706040700002006057700001906077700001606096700002006112700001606132700001906148700001806167700001906185700001706204700001506221700001606236700001706252700001806269856007406287 2018 eng d00aPartitioning assimilatory nitrogen uptake in streams: an analysis of stable isotope tracer additions across continents0 aPartitioning assimilatory nitrogen uptake in streams an analysis a1380 v883 a

Headwater streams remove, transform, and store inorganic nitrogen (N) delivered from surrounding watersheds, but excessive N inputs from human activity can saturate removal capacity. Most research has focused on quantifying N removal from the water column over short periods and in individual reaches, and these ecosystem-scale measurements suggest that assimilatory N uptake accounts for most N removal. However, cross-system comparisons addressing the relative role of particular biota responsible for incorporating inorganic N into biomass are lacking. Here we assess the importance of different primary uptake compartments on reach-scale ammonium (NH4+-N) uptake and storage across a wide range of streams varying in abundance of biota and local environmental factors. We analyzed data from 17 15N-NH4+tracer addition experiments globally, and found that assimilatory N uptake by autotrophic compartments (i.e., epilithic biofilm, filamentous algae, bryophytes/macrophytes) was higher but more variable than for heterotrophic microorganisms colonizing detrital organic matter (i.e., leaves, small wood, and fine particles). Autotrophic compartments played a disproportionate role in N uptake relative to their biomass, although uptake rates were similar when we rescaled heterotrophic assimilatory N uptake associated only with live microbial biomass. Assimilatory NH4+-N uptake, either estimated as removal from the water column or from the sum uptake of all individual compartments, was four times higher in open- than in closed-canopy streams. Using Bayesian Model Averaging, we found that canopy cover and gross primary production (GPP) controlled autotrophic assimilatory N uptake while ecosystem respiration (ER) was more important for the heterotrophic contribution. The ratio of autotrophic to heterotrophic N storage was positively correlated with metabolism (GPP: ER), which was also higher in open- than in closed-canopy streams. Our analysis shows riparian canopy cover influences the relative abundance of different biotic uptake compartments and thus GPP:ER. As such, the simple categorical variable of canopy cover explained differences in assimilatory N uptake among streams at the reach scale, as well as the relative roles of autotrophs and heterotrophs in N storage. Finally, this synthesis links cumulative N uptake by stream biota to reach-scale N demand and provides a mechanistic and predictive framework for estimating and modeling N cycling in other streams.

1 aTank, J.L.1 aMarti, E.1 aRiis, T.1 avon Schiller, D.1 aReisinger, A.J.1 aDodds, W., K.1 aWhiles, M.R.1 aAshkenas, L.R.1 aBowden, W.B.1 aCollins, S., M.1 aCrenshaw, C.L.1 aCrowl, T.A.1 aGriffiths, N.A.1 aGrimm, N.B.1 aHamilton, S.K.1 aJohnson, S.L.1 aMcDowell, W.H.1 aNorman, B.M.1 aRosi, E.J.1 aSimon, K.S.1 aThomas, S.A.1 aWebster, J.R. uhttps://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecm.128002509nas a2200157 4500008004100000245010900041210006900150300001200219490000700231520197000238100002302208700002302231700001802254700001802272856006102290 2018 eng d00aTop - down effects of a grazing, omnivorous minnow (Campostoma anomalum) on stream microbial communities0 aTop down effects of a grazing omnivorous minnow Campostoma anoma a121-1330 v373 a

Top–down control exerted by macroconsumers can strongly affect lower trophic levels and ecosystem processes. Studies of effects on primary consumers in streams have been focused on algae, and effects on bacteria are largely unknown. We manipulated the density of an omnivorous, grazing minnow, the central stoneroller (Campostoma anomalum), in experimental stream mesocosms (treatments with 0, 1, 2, 3, 4, 5, 6, or 7 individuals) to understand consumer effects on algal and bacterial abundance (chlorophyll a [Chl a] extraction, bacterial cell counts, biomass measurements) and bacterial diversity and community composition (via Illumina MiSeq sequencing of the V4 region of the 16S ribosomal RNA gene). Increasing C. anomalum density reduced algal biomass until density reached ~2 fish (5 g fish biomass/m2), and higher fish densities did not affect algal biomass. Fish biomass did not affect bacterial cell counts. Biofilm organic matter decreased with increasing C. anomalum biomass. Bacterial community composition was not affected by fish biomass, but variation in community composition was correlated with shifts in bacterial abundances. Evenness of bacterial operational taxonomic units (OTUs) decreased with increasing C. anomalum biomass, indicating that bacterial communities exhibited a greater degree of OTU dominance when fish biomass was higher. These findings suggest that this grazing fish species reduces algal abundance and organic matter in low-nutrient streams until a threshold of moderate fish abundance is reached and that it reduces evenness of benthic bacterial communities but not bacterial biomass. Given the importance of biofilm bacteria for ecosystem processes and the ubiquity of grazing fishes in streams, future researchers should explore both top–down and bottom–up interactions in alternative environmental contexts and with other grazing fish species.

1 aVeach, Allison, M.1 aTroia, Matthew, J.1 aJumpponen, A.1 aDodds, W., K. uhttps://www.journals.uchicago.edu/doi/abs/10.1086/69629203381nas a2200409 4500008004100000245007100041210006900112300000900181490000700190520222500197100001902422700001902441700002002460700002002480700002102500700002002521700002602541700001902567700001702586700002102603700001402624700001802638700001702656700001902673700002202692700001402714700002102728700002102749700002002770700001302790700001802803700001702821700001902838700002102857700002002878856007302898 2017 eng d00aDrivers of nitrogen transfer in stream food webs across continents0 aDrivers of nitrogen transfer in stream food webs across continen a30550 v983 a

Studies of trophic-level material and energy transfers are central to ecology. The use of isotopic tracers has now made it possible to measure trophic transfer efficiencies of important nutrients and to better understand how these materials move through food webs. We analyzed data from thirteen 15N-ammonium tracer addition experiments to quantify N transfer from basal resources to animals in headwater streams with varying physical, chemical, and biological features. N transfer efficiencies from primary uptake compartments (PUCs; heterotrophic microorganisms and primary producers) to primary consumers was lower (mean 11.5%, range <1% to 43%) than N transfer efficiencies from primary consumers to predators (mean 80%, range 5% to >100%). Total N transferred (as a rate) was greater in streams with open compared to closed canopies and overall N transfer efficiency generally followed a similar pattern, although was not statistically significant. We used principal component analysis to condense a suite of site characteristics into two environmental components. Total N uptake rates among trophic levels were best predicted by the component that was correlated with latitude, DIN:SRP, GPP:ER, and percent canopy cover. N transfer efficiency did not respond consistently to environmental variables. Our results suggest that canopy cover influences N movement through stream food webs because light availability and primary production facilitate N transfer to higher trophic levels.

1 aNorman, B., C.1 aWhiles, M., R.1 aCollins, S., M.1 aFlecker, A., S.1 aHamilton, S., K.1 aJohnson, S., L.1 aRosi-Marshall, E., J.1 aAshkenas, L.R.1 aBowden, W.B.1 aCrenshaw, C., L.1 aCrowl, T.1 aDodds, W., K.1 aHall, R., O.1 aEl-Sabaawi, R.1 aGriffiths, N., A.1 aMarti, E.1 aMcDowell, W., H.1 aPeterson, S., D.1 aRantala, H., M.1 aRiis, T.1 aSimon, K., S.1 aTank, J., L.1 aThomas, S., A.1 avon Schiller, D.1 aWebster, J., R. uhttps://esajournals.onlinelibrary.wiley.com/doi/abs/10.1002/ecy.200903014nas a2200301 4500008004100000245009900041210006900140300001400209490000700223520204700230100002402277700002402301700002002325700001802345700002202363700002702385700002502412700002402437700002002461700002102481700002602502700002202528700002702550700002602577700002502603700002202628856006202650 2017 eng d00aGlobal synthesis of the temperature sensitivity of leaf litter breakdown in streams and rivers0 aGlobal synthesis of the temperature sensitivity of leaf litter b a3064-30750 v233 a

Streams and rivers are important conduits of terrestrially derived carbon (C) to atmospheric and marine reservoirs. Leaf litter breakdown rates are expected to increase as water temperatures rise in response to climate change. The magnitude of increase in breakdown rates is uncertain, given differences in litter quality and microbial and detritivore community responses to temperature, factors that can influence the apparent temperature sensitivity of breakdown and the relative proportion of C lost to the atmosphere vs. stored or transported downstream. Here, we synthesized 1025 records of litter breakdown in streams and rivers to quantify its temperature sensitivity, as measured by the activation energy (Ea, in eV). Temperature sensitivity of litter breakdown varied among twelve plant genera for which Ea could be calculated. Higher values of Ea were correlated with lower-quality litter, but these correlations were influenced by a single, N-fixing genus (Alnus). Ea values converged when genera were classified into three breakdown rate categories, potentially due to continual water availability in streams and rivers modulating the influence of leaf chemistry on breakdown. Across all data representing 85 plant genera, the Ea was 0.34 ± 0.04 eV, or approximately half the value (0.65 eV) predicted by metabolic theory. Our results indicate that average breakdown rates may increase by 5–21% with a 1–4 °C rise in water temperature, rather than a 10–45% increase expected, according to metabolic theory. Differential warming of tropical and temperate biomes could result in a similar proportional increase in breakdown rates, despite variation in Ea values for these regions (0.75 ± 0.13 eV and 0.27 ± 0.05 eV, respectively). The relative proportions of gaseous C loss and organic matter transport downstream should not change with rising temperature given that Ea values for breakdown mediated by microbes alone and microbes plus detritivores were similar at the global scale.

1 aFollstad-Shah, J.J.1 aKominoski, John, S.1 aArdón, Marcelo1 aDodds, W., K.1 aGessner, Mark, O.1 aGriffiths, Natalie, A.1 aHawkins, Charles, P.1 aJohnson, Sherri, L.1 aLecerf, Antoine1 aLeRoy, Carri, J.1 aManning, David, W. P.1 aRosemond, Amy, D.1 aSinsabaugh, Robert, L.1 aSwan, Christopher, M.1 aWebster, Jackson, R.1 aZeglin, Lydia, H. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.1360903044nas a2200157 4500008004100000245009000041210006900131300001400200490000700214520252100221100002102742700002402763700001902787700001802806856006202824 2017 eng d00aProbing whole-stream metabolism: influence of spatial heterogeneity on rate estimates0 aProbing wholestream metabolism influence of spatial heterogeneit a711 - 7230 v623 a

1. Whole-stream metabolism has been estimated by measuring in-stream oxygen (O2) concentrations since the method was introduced over 50 years ago. However, the influence of measurement location and estimation method on metabolism rates is understudied. We examined how the placement of O2 probes (i.e. depth, separation from the thalweg), differences in methodology (1-station, 2-station, area-weighted) and reach lengths influenced estimated rates of whole-stream metabolism in a tallgrass prairie watershed.

2. Metabolism estimates made in the thalweg differed from estimates made in backwaters due to disconnection in flow, and estimates made in deep pools differed from surface estimates due to thermal stratification (temporary flow disconnection). The 1-station respiration estimates differed from short 2-station reach-scale estimates (c. 20 m) but were more similar to larger 2-station reach-scale estimates (c. 100 m). In contrast, the 1-station gross primary production was most similar to the short 2-station reaches occurring immediately upstream and became less similar at longer 2-station reach lengths. The different estimation methodologies (1-station, 2-station, area-weighted) accounting for the longest reach scale did not result in different metabolism rates.

3. The temporary phenomena of thermal stratification of stream pools during a warm day, which disconnected pool bottoms from the surface waters, likely affected not only the pool estimates but also estimates made in the downstream thalweg (i.e. an O2 deficit accrued from respiration during the day in the bottom of the pool abruptly moved downstream during mixing).

4. Oxygen probe placement mattered and affected rate estimates according to habitat type and reach length (i.e. scale) due to the influence of small-scale heterogeneity on community respiration. Selection of reach length can be critical for studies depending on whether local heterogeneity is of interest or should be averaged.

5. We conclude that the intuitive use of thalwegs and reaches that are at least 10 times the stream width are likely appropriate for whole-stream metabolism estimates, although the exact reach length necessary and potential stream-specific characteristics, such as stratified pools, need to be carefully considered in probe placement. We encourage other studies to report the placement characteristics of O2 probes in streams as well as consider the potential confounding factor of local habitat heterogeneity.

1 aSiders, Adam, C.1 aLarson, Danelle, M.1 aRüegg, Janine1 aDodds, W., K. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/fwb.1289603056nas a2200409 4500008004100000022001400041245011300055210006900168300001200237490000700249520184200256653001802098653001802116653001502134653001702149653001202166653002102178100001902199700001802218700001802236700002102254700002502275700001702300700002502317700002302342700002202365700001602387700002302403700002402426700001902450700002302469700002202492700002302514700001702537700002602554856006602580 2016 eng d a0921-297300aBaseflow physical characteristics differ at multiple spatial scales in stream networks across diverse biomes0 aBaseflow physical characteristics differ at multiple spatial sca a119-1360 v313 a

Context Spatial scaling of ecological processes is facilitated by quantifying underlying habitat attributes. Physical and ecological patterns are often measured at disparate spatial scales limiting our ability to quantify ecological processes at broader spatial scales using physical attributes. Objective We characterized variation of physical stream attributes during periods of high biological activity (i.e., baseflow) to match physical and ecological measurements and to identify the spatial scales exhibiting and predicting heterogeneity. Methods We measured canopy cover, wetted width, water depth, and sediment size along transects of 1st–5th order reaches in five stream networks located in biomes from tropical forest to arctic tundra. We used hierarchical analysis of variance with three nested scales (watersheds, stream orders, reaches) to identify scales exhibiting significant heterogeneity in attributes and regression analyses to characterize gradients within and across stream networks. Results Heterogeneity was evident at one or multiple spatial scales: canopy cover and water depth varied significantly at all three spatial scales while wetted width varied at two scales (stream order and reach) and sediment size remained largely unexplained. Similarly, prediction by drainage area depended on the attribute considered: depending on the watershed, increases in wetted width and water depth with drainage area were best fit with a linear, logarithmic, or power function. Variation in sediment size was independent of drainage area. Conclusions The scaling of ecologically relevant baseflow physical characteristics will require study beyond the traditional bankfull geomorphology since predictions of baseflow physical attributes by drainage area were not always best explained by geomorphic power laws.

10aBoreal forest10aGeomorphology10aGrasslands10aNested ANOVA10aScaling10aTemperate forest1 aRüegg, Janine1 aDodds, W., K.1 aDaniels, M.D.1 aSheehan, Ken, R.1 aBaker, Christina, L.1 aBowden, W.B.1 aFarrell, Kaitlin, J.1 aFlinn, Michael, B.1 aHarms, Tamara, K.1 aJones, J.B.1 aKoenig, Lauren, E.1 aKominoski, John, S.1 aMcDowell, W.H.1 aParker, Samuel, P.1 aRosemond, Amy, D.1 aTrentman, Matt, T.1 aWhiles, M.R.1 aWollheim, Wilfred, M. uhttps://link.springer.com/article/10.1007%2Fs10980-015-0289-y02612nas a2200169 4500008004100000245010100041210006900142300001600211490000700227520203500234100001702269700001802286700001702304700002202321700001802343856008102361 2016 eng d00aA before-and-after assessment of patch-burn grazing and riparian fencing along headwater streams0 abeforeandafter assessment of patchburn grazing and riparian fenc a1543–15530 v533 a
  1. Fire and grazing are common in grasslands world-wide to maintain grass cover and cattle production. The effects of fire, cattle grazing and riparian fencing efficacy on prairie stream ecology are not well characterized at catchment scales.
  2. We examined alterations to stream water quality and biology from patch-burn grazing (PBG) in tallgrass prairie during a five-year, replicated, catchment scale experiment that used a Before-After/Control-Impact (BACI) design and was analysed by mixed-effects models. Treatments included two patch-burned control catchments (fire but no grazers) and PBG in two riparian-fenced and two unfenced catchments. We assessed the effectiveness of riparian fencing for mitigating potential water quality impacts by monitoring water quality and riparian usage by cattle via Global Positioning System.
  3. Riparian fences effectively excluded cattle; however, in unfenced pastures, cattle aggregated along streams 10–20% of the grazing season.
  4. After initiation of PBG, we detected large increases in some nutrients, Escherichia coli, algal biomass, primary productivity and community respiration in all catchments with PBG. Some water quality variables, such as E. coli concentrations, recovered quickly after cattle were removed from pasture, which indicated resiliency.
  5. Riparian fencing moderately reduced the impacts to stream variables, indicating either overland flow and/or subsurface flow allowed nutrients and bacteria to enter the streams.
  6. Synthesis and applications. Patch-burn grazing is a measurable disturbance that can alter the ecological condition of streams. Riparian fencing lessened the degree of impact, yet some water quality variables still exceeded regional reference conditions. Managers will need to assess the costs of riparian fencing compared to the moderate benefits that fencing provides to water quality.
1 aLarson, D.M.1 aDodds, W., K.1 aWhiles, M.R.1 aThompson, T.R., .1 aFulgoni, J.N. uhttps://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2664.1269202655nas a2200229 4500008004100000022001400041245014200055210006900197300001400266490000700280520192200287653002402209653001502233653001802248653001302266653001802279653001402297100001502311700001802326700001502344856006602359 2016 eng d a1015-162100aCharacterizing organic matter inputs to sediments of small, intermittent, prairie streams: a molecular marker and stable isotope approach0 aCharacterizing organic matter inputs to sediments of small inter a343 - 3540 v783 a

Small rivers and streams are ecologically important because they contribute to the export of organic carbon to coastal environments, likely influencing the global carbon cycle. While organic matter (OM) dynamics in large rivers has been studied in quite some detail, less is known about small streams. Sources of OM in streams ultimately determine its availability to the food web and downstream transport. In this study, sediment samples were collected from the King’s Creek watershed in Konza Prairie (Kansas, USA) and analyzed using molecular biomarkers and bulk 13C stable isotopes with the objective to comparatively assess OM inputs between riparian forest vegetation and watershed grassland to small, intermittent streams. We are interested in the potential influence of woody riparian expansion that has been ongoing at the site. Biomarkers typical of the local C4 grasses (branched n-alkanes, phytadienes) were more abundant in some of the sediments of the upper reaches. The sediments of the lower reaches contained biomarkers of algae (short-chain aliphatic compounds, C25:5 highly branched isoprenoid, brassicasterol) and vascular plant-derived material (triterpenols). Degraded OM (triterpene/triterpenol ratio) was found throughout the watershed with no pattern between the upper and lower reaches. Bulk 13C isotope analysis showed that the upper reaches of the watershed receive significant OM inputs from the C4 grasses (74–99 %) while the lower reaches are more strongly influenced by riparian trees (26–27 %) and algae (21–22 %). These results suggest that the environmental dynamics of bulk OM and the biomarker composition of small prairie streams are highly complex and likely a function of several factors such as light availability, riparian vegetative composition and density, and varying degrees of OM storage, retention and transport along the river continuum.

10a13C stable isotopes10aBiomarkers10aKonza Prairie10aRiparian10aSmall streams10aWatershed1 aPisani, O.1 aDodds, W., K.1 aJaffé, R. uhttps://link.springer.com/article/10.1007%2Fs00027-015-0435-202824nas a2200169 4500008004100000245011800041210006900159300001400228490000700242520226100249100001702510700001702527700001402544700001802558700001602576856006202592 2016 eng d00aIncreasing fish taxonomic and functional richness affects ecosystem properties of small headwater prairie streams0 aIncreasing fish taxonomic and functional richness affects ecosys a887–8980 v613 a

1. Stream fish can regulate their environment through direct and indirect pathways, and the relative influence of communities with different taxonomic and functional richness on ecosystem properties likely depends on habitat structure. Given this complexity, it is not surprising that observational studies of how stream fish communities influence ecosystems have shown mixed results. 2. In this study, we evaluated the effect of an observed gradient of taxonomic (zero, one, two or three species) and functional (zero, one or two groups) richness of fishes on several key ecosystem properties in experimental stream mesocosms. Our study simulated small (less than two metres wide) headwater prairie streams with a succession of three pool-riffle structures (upstream, middle and downstream) per mesocosm. Ecosystem responses included chlorophyll a from floating algal mats and benthic algae, benthic organic matter, macroinvertebrates (all as mass per unit area), algal filament length and stream metabolism (photosynthesis and respiration rate). Ecosystem responses were analysed individually using general linear mixed models. 3. Significant treatment (taxonomic and functional richness) by habitat (pools and riffles) interactions were found for all but one ecosystem response variable. After accounting for location (upstream, middle and downstream) effects, the presence of one or two grazers resulted in shorter mean algal filament lengths in pools compared to no-fish controls. These observations suggest grazers can maintain short algal filaments in pools, which may inhibit long filaments from reaching the surface. Accordingly, floating algal mats decreased in mid- and downstream locations in grazer treatment relative to no-fish controls. 4. At the scale of the entire reach, gross primary productivity and respiration were greater in treatments with two grazer species compared to mixed grazer/insectivore or control treatments. 5. The distribution of stream resources across habitat types and locations within a reach can therefore be influenced by the taxonomic and functional composition of fishes in small prairie streams. Thus, disturbances that alter diversity of these systems might have unexpected ecosystem-level consequences.

1 aMartin, E.D.1 aGido, K., B.1 aBello, N.1 aDodds, W., K.1 aVeach, A.M. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/fwb.1275202310nas a2200169 4500008004100000245007800041210006900119300001400188490000700202520176200209100001501971700001801986700002302004700001902027700002102046856007302067 2016 eng d00aMethods of approximation influence aquatic ecosystem metabolism estimates0 aMethods of approximation influence aquatic ecosystem metabolism  a557 - 5690 v143 a

Aquatic ecologists have recently employed dynamic models to estimate aquatic ecosystem metabolism. All approaches involve numerically solving a differential equation describing dissolved oxygen (DO) dynamics. Although the DO differential equation can be solved accurately with linear multistep or Runge–Kutta methods, less accurate methods, such as the Euler method, have been applied. The methods also differ in how discrete temperature and light measurements are used to drive DO dynamics. Here, we used a representative stream DO data set to compare the metabolism estimates generated by multiple Euler based methods and an accurate numerical method. We also compared metabolism estimates using linear, piecewise constant and smoothing spline interpolation of light and temperature. Using observed DO to calculate DO saturation deficit in the Euler method results in a substantial difference in metabolism estimates compared to all other methods. If modeled DO is used to calculate DO saturation deficit, the Euler method introduces smaller error in metabolism estimates, which diminishes as logging interval decreases. Linear and smoothing spline interpolation result in similar metabolism estimates, but differ from estimates based on piecewise constant interpolation. We demonstrate how different computational methods imply distinct assumptions about process and observation error, and conclude that under the assumption of observation error, the best practice is to use the accurate numerical method of solving differential equation with a continuous interpolation of light and temperature. The Euler method will introduce minimal error if it is paired with frequently logged data and DO saturation deficit is computed using modeled DO.

1 aSong, Chao1 aDodds, W., K.1 aTrentman, Matt, T.1 aRüegg, Janine1 aBallantyne, Ford uhttps://aslopubs.onlinelibrary.wiley.com/doi/full/10.1002/lom3.1011201954nas a2200181 4500008004100000245005600041210005400097300001400151490000600165520144900171653001901620653001301639653001501652653001201667100001801679700001601697856005901713 2016 eng d00aNitrogen, phosphorus, and eutrophication in streams0 aNitrogen phosphorus and eutrophication in streams a155 - 1640 v63 a

Flowing waters receive substantial nutrient inputs, including both nitrogen (N) and phosphorus (P), in many parts of the world. Eutrophication science for rivers and streams has unfortunately lagged behind that for lakes, and results from lakes might inform those interested in stream eutrophication. A key controversy in lake eutrophication science is the relative importance of controlling P and N in water quality management, and we are interested how the science of this controversy transfers to flowing waters. A literature review indicates (1) stream benthic chlorophyll is significantly correlated to both total N and total P in the water column, with both nutrients explaining more variance than either considered alone; (2) nutrients have increased substantially in many rivers and streams of the United States over reference conditions, and strong shifts in N and P stoichiometry have occurred as well; (3) bioassays often indicate N responses alone or in concert with P responses for autotrophic (primary production and chlorophyll) and heterotrophic (respiration) responses; (4) both heterotrophic and autotrophic processes are influenced by the availability of N and P; and (5) N-fixing cyanobacteria usually do not seem to be able to fully satisfy N limitations in rivers and streams when P is present in excess of N. These data suggest both N and P control should be considered in the eutrophication management of streams.

10aeutrophication10anitrogen10aPhosphorus10astreams1 aDodds, W., K.1 aSmith, V.H. uhttps://www.tandfonline.com/doi/abs/10.5268/IW-6.2.90902397nas a2200169 4500008004100000245010300041210006900144300001600213490000700229520184400236100001602080700001702096700001602113700001802129700001802147856006202165 2016 eng d00aSpatial and successional dynamics of microbial biofilm communities in a grassland stream ecosystem0 aSpatial and successional dynamics of microbial biofilm communiti a4674 - 46880 v253 aBiofilms represent a metabolically active and structurally complex component of freshwater ecosystems. Ephemeral prairie streams are hydrologically harsh and prone to frequent perturbation. Elucidating both functional and structural community changes over time within prairie streams provides a general understanding of microbial responses to environmental disturbance. We examined microbial succession of biofilm communities at three sites in a third-order stream at Konza Prairie over a 2- to 64-day period. Microbial abundance (bacterial abundance, chlorophyll a concentrations) increased and never plateaued during the experiment. Net primary productivity (net balance of oxygen consumption and production) of the developing biofilms did not differ statistically from zero until 64 days suggesting a balance of the use of autochthonous and allochthonous energy sources until late succession. Bacterial communities (MiSeq analyses of the V4 region of 16S rRNA) established quickly. Bacterial richness, diversity and evenness were high after 2 days and increased over time. Several dominant bacterial phyla (Beta-, Alphaproteobacteria, Bacteroidetes, Gemmatimonadetes, Acidobacteria, Chloroflexi) and genera (Luteolibacter, Flavobacterium, Gemmatimonas, Hydrogenophaga) differed in relative abundance over space and time. Bacterial community composition differed across both space and successional time. Pairwise comparisons of phylogenetic turnover in bacterial community composition indicated that early-stage succession (≤16 days) was driven by stochastic processes, whereas later stages were driven by deterministic selection regardless of site. Our data suggest that microbial biofilms predictably develop both functionally and structurally indicating distinct successional trajectories of bacterial communities in this ecosystem.1 aVeach, A.M.1 aStagen, J.C.1 aBrown, S.P.1 aDodds, W., K.1 aJumpponen, A. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/mec.1378402475nas a2200205 4500008004100000245013900041210006900180300001400249490000800263520178600271653001702057653001802074653002002092653002002112100001502132700002102147700001702168700001802185856006602203 2015 eng d00aDissolved organic carbon concentration and flux in a grassland stream: spatial and temporal patterns and processes from long-term data0 aDissolved organic carbon concentration and flux in a grassland s a393 - 4080 v1253 a

Dissolved organic carbon (DOC) in streams is a critical component of the global carbon cycle, but little is known about long-term patterns in DOC concentration and export in grassland streams. Here we present the results of a 15-year dataset collected from multiple sites in the Kings Creek watershed on Konza Prairie, KS, USA. DOC concentrations ranged from 0.15 to 15.97 mg L−1, with a mean of 1.19 mg L−1 (standard deviation 1.01 mg L−1). Sites differed in their DOC concentrations as a function of the year of study and the season. Generally, headwaters had greater DOC concentrations, and DOC decreased downstream. The lowest concentrations were found in a groundwater spring in the watershed. Concentrations showed no trend over the study and were not correlated with discharge. However, annual export (mean: 0.29 kg ha−1 year−1; range: 0.00–9.09 kg ha−1 year−1) was highly correlated with annual runoff, and annual runoff explained over 80 % of the variation in export. Export from Kings Creek was 30 times lower than the literature-reported mean for grasslands and 137 times less than export averaged across all biomes. Neither fire nor bison, two forces that maintain prairies, were statistically related to DOC concentrations. Main drivers of DOC concentrations are likely leaching from terrestrial organic material in soils and the accumulations in dry streambeds during drought periods as well as instream autotrophic production. Downstream declines in DOC concentrations suggest instream processing. Grassland streams probably have modest effects on the global carbon budget due to instream processing and low precipitation. Changes in precipitation may have large effects on carbon export from grassland streams.

10acarbon cycle10aCarbon export10along-term study10aprairie streams1 aRüegg, J.1 aEichmiller, J.J.1 aMladenov, N.1 aDodds, W., K. uhttps://link.springer.com/article/10.1007%2Fs10533-015-0134-z03029nas a2200157 4500008004100000245009200041210006900133260004300202490002200245520236400267653008102631100001602712700001802728700001802746856010702764 2015 eng d00aDynamics of microbial community structure and function in a tallgrass prairie ecosystem0 aDynamics of microbial community structure and function in a tall aManhattan, KSbKansas State University0 vPhD. Dissertation3 a

Due to agricultural practices and urbanization, tallgrass prairie ecosystems have become threatened as < 5% of its historical coverage exists today. The small remainder of praire that does exist is further threatened by the encroachment of woody plant species. Woody plant encroachment may not only alter prairie ecosystem function, but also prairie microbial communities responsible for these functional processes. Further, prairies are high disturbance ecosystems, especially prairie streams which are hydrologically harsh. They support communities that frequently undergo succession due to recurring flood and drought conditions, yet little is known about the response of microbial communities to these disturbances. In my dissertation, I first address the degree of woody vegetation expansion in riparian corridors (parallel to streams) in watersheds with variable fire frequency and grazing. I found that the rate of riparian woody expansion declines with higher fire intervals and is not affected by grazing, but even annual burns may not prevent woody plant expansion in riparian zones from occurring. Second, I quantified the effect of using restorations of riparian corridors, through removal of woody plants, on physical, chemical, and microbial community (bacteria and fungi) dynamics across stream to upslope soils. Removal restoration causes a decrease in NH₄⁺ and soil water content, and causes streams and upslope soils to become similar in fungal community richness unlike forested landscapes. Bacterial communities were minimally impacted by removals, but were highly structured among stream to upslope soils due to multiple environmental gradients (i.e., pH, NO₃⁻, soil moisture). Lastly, I examined the successional development of biofilm-associated microbial communities in a prairie stream from both a functional and structural perspective. I found that biofilm microbes exhibited strong successional trajectories, with communities developing towards net autotrophy and therefore becoming reliant upon in-stream derived carbon. Further, bacterial communities displayed spatial differences, but much stronger temporal patterns in community composition were detected. These studies highlight how woody plant encroachment may influence stream ecosystems in addition to spatiotemporal trends in microbial community assembly.

10aMicrobial communities; Woody encroachment; Bacteria; Fungi; Biofilms; Stream1 aVeach, A.M.1 aDodds, W., K.1 aJumpponen, A. uhttp://krex.k-state.edu/dspace/bitstream/handle/2097/19145/AllisonVeach2015.pdf?sequence=1&isAllowed=y02156nas a2200205 4500008004100000245011400041210006900155300001400224490000800238520148900246653001001735653001701745653001701762653001201779653002101791100001901812700001801831700001801849856008301867 2015 eng d00aFundamental spatial and temporal disconnections in the hydrology of an intermittent prairie headwater network0 aFundamental spatial and temporal disconnections in the hydrology a305 - 3160 v5223 a

We characterize the hydrology of intermittent prairie headwater streams of the Konza Prairie Biological Station (Konza) located in northeastern Kansas, USA. Flow records from four gaging stations were used to quantify flow intermittence and mean and peak annual discharges. Gage sites used in this analysis are classified as harshly intermittent with all sites having over 90 days of zero-flow annually. The largest basin had the fewest zero-flow days and the shortest durations of zero-flow while the smallest basin had the most zero-flow days and the highest frequency zero-flow durations. There were strong correlations between total annual precipitation and the total number of zero-flow days and the number of zero-flow periods. Correlations were less strong between the Palmer Drought Severity Index (PDSI) and the number of zero-flow days and between PDSI and the number of zero-flow periods. Basin-averaged total annual precipitation poorly predicted mean annual and peak annual discharges. Double mass plots of streamflow to precipitation and streamflow in the headwaters to the receiving stream demonstrate many instances of flow desynchronization. Results of this study suggest that local watershed-scale processes, such as groundwater storage in limestone and alluvial strata, dynamic infiltration flow paths, and soil moisture conditions, produce a threshold-driven hydrologic response, decoupling the headwater hydrologic regimes from sub-annual weather patterns.

10aFlood10aGreat Plains10aIntermittent10aprairie10aTemporary stream1 aCostigan, K.H.1 aDaniels, M.D.1 aDodds, W., K. uhttps://www.sciencedirect.com/science/article/pii/S0022169414010427?via%3Dihub02956nas a2200313 4500008004100000245012400041210006900165300001400234490000700248520203700255100001802292700001702310700001802327700001702345700001502362700001802377700001602395700001402411700001702425700001702442700001502459700001902474700001902493700001902512700001402531700001802545700001702563856006202580 2015 eng d00aLong-term changes in structure and function of a tropical headwater stream following a disease-driven amphibian decline0 aLongterm changes in structure and function of a tropical headwat a575 - 5890 v603 a

1. Taxonomic and functional diversity in freshwater habitats is rapidly declining, but we know little about how such declines will ultimately affect ecosystems. Neotropical streams are currently experiencing massive losses of amphibians, with many losses linked to the chytrid fungus, Batrachochytrium dendrobatidis (Bd). 2. We examined the ecological consequences of the disease-driven loss of amphibians from a Panamanian stream. We quantified basal resources, macroinvertebrates, N uptake and fluxes through food-web components and ecosystem metabolism in 2012 and 2014 and compared them to pre-decline (2006) and 2 year post-decline (2008) values from a prior study. 3. Epilithon biomass accrued after the decline, more than doubling between 2006 and 2012, but then decreased fivefold from 2012 to 2014. In contrast, suspended particulate organic matter (SPOM) concentrations declined continuously after the amphibian decline through 2014. 4. Biomass of filter-feeding, grazing and shredding macroinvertebrates decreased from 2006 to 2014, while collector–gatherers increased during the same time period. Macroinvertebrate taxa richness decreased from 2006 (52 taxa) to 2012 (30 taxa), with a subsequent increase to 51 taxa in 2014. 5. Community respiration, which initially decreased after the amphibian decline, remained lower than pre-decline in 2012 but was greater than pre-decline values in 2014. Gross primary production remained low and similar among years, while inline image uptake length in both 2012 and 2014 was longer than pre-decline. Nitrogen flux to epilithon increased after the decline and continued to do so through 2014, but N fluxes to fine particulate organic matter and SPOM decreased and remained low. 6. Our findings underscore the importance of studying the ecological consequences of declining biodiversity in natural systems over relatively long time periods. There was no evidence of functional redundancy or compensation by other taxa after the loss of amphibians, even after 8 years.

1 aRantala, H.M.1 aNelson, A.M.1 aFulgoni, J.N.1 aWhiles, M.R.1 aHall, R.O.1 aDodds, W., K.1 aVerburg, P.1 aHuryn, A.1 aPringle, C..1 aKilham, S.S.1 aLips, K.R.1 aColon-Gaud, C.1 aRugenski, A.T.1 aPeterson, S.D.1 aFritz, K.1 aMcLeran, K.E.1 aConnelly, S. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/fwb.1250502359nas a2200181 4500008004100000245008800041210006900129300000900198490000700207520178200214100001801996700001702014700001802031700001602049700002102065700001802086856007302104 2015 eng d00aPatch-burn grazing effects on the ecological integrity of tallgrass prairie streams0 aPatchburn grazing effects on the ecological integrity of tallgra a11480 v443 a

Conversion to agriculture, habitat fragmentation, and the loss of native grazers have made tallgrass prairie one of the most endangered ecosystems. One management option for the remaining prairie parcels, patch-burn grazing (PBG), applies a controlled burn to a portion of the prairie to attract cattle, creating a mosaic of more- and less-grazed patches. Although beneficial to cattle and grassland birds, the potential impacts of PBG on streams have not been studied, and a holistic approach is needed to ensure against adverse effects. We used a Before-After-Control-Impact design to assess potential impacts of PBG with and without riparian protection on tallgrass prairie headwater streams. We sampled stream macroinvertebrates and benthic organic matter 2 yr before and 2 yr during PBG treatments on two grazed watersheds with riparian fencing (fenced), two unfenced grazed watersheds (unfenced), and two ungrazed (control) watersheds. Very fine benthic organic matter increased significantly (51%) in unfenced streams compared with controls ( < 0.007), and fine particulate organic matter (<1 mm and >250 µm) increased 3-fold in the unfenced streams compared with controls ( = 0.008). The contribution of fine inorganic sediments to total substrata increased 28% in unfenced streams during PBG, which was significantly different from controls ( = 0.03). Additionally, the abundance of Ephemeroptera, Plecoptera, and Trichoptera taxa decreased from 7635 to 687 individuals m in unfenced streams, which was significantly lower than in control streams ( = 0.008). Our results indicate that PBG adversely influences prairie streams through sediment inputs and reductions in sensitive invertebrate taxa, but riparian fencing can alleviate these impacts.

1 aJackson, K.E.1 aWhiles, M.R.1 aDodds, W., K.1 aReeve, J.D.1 aVandermyde, J.M.1 aRantala, H.M. uhttps://dl.sciencesocieties.org/publications/jeq/abstracts/44/4/114802563nas a2200253 4500008004100000245017400041210006900215300001200284490000800296520173200304653002002036653002302056653001002079653001802089100001902107700001802126700001602144700001502160700001702175700001902192700001702211700001502228856006602243 2015 eng d00aQuantifying ambient nitrogen uptake and functional relationships of uptake versus concentration in streams: a comparison of stable isotope, pulse, and plateau approaches0 aQuantifying ambient nitrogen uptake and functional relationships a65 - 790 v1253 a

Nutrient releases and spiraling metrics are frequently used to quantify the downstream transport of nutrients and to better understand the effects of anthropogenic inputs to downstream waters. Ambient uptake rates in streams can be measured through stable isotope enrichments, while pulse and plateau additions can estimate such rates via extrapolation and modeling techniques, respectively. Data from these releases can be used to estimate ambient uptake rates from nutrient additions and possibly determine the functional relationships between nutrient concentrations and uptake rates. Here, we compared estimated ambient rates calculated from established pulse and plateau approaches, results obtained from new modeling approaches, and rates at ambient concentrations from stable isotope enrichments. Comparative releases of NH4Cl and 15NH4Cl were conducted in four experimental reaches across the grassland Kings Creek and urban Campus Creek, KS. Nutrient uptake was predominantly linear with increasing ammonium. Estimated ambient uptake rates varied among sites, release methods, and data analysis approaches. However, plateau ambient rates from new modeling approaches matched closely with measured ambient rates from isotope enrichments at three sites, suggesting that modeled plateau data may be best for a first look at determining nutrient uptake rates at an individual site. Limitations and benefits of each approach vary; however, baseflow discharge may be a key driver when choosing a method. If possible, multiple methods should be attempted at each location and under each novel set of conditions to determine the best approach prior to designing and implementing a more extensive series of measurements.

10aAmmonium uptake10anutrient spiraling10aTASCC10auptake length1 aTrentman, M.T.1 aDodds, W., K.1 aFencl, J.S.1 aGerber, K.1 aGuarneri, J.1 aHitchman, S.M.1 aPeterson, Z.1 aRüegg, J. uhttps://link.springer.com/article/10.1007%2Fs10533-015-0112-502375nas a2200241 4500008004100000245010700041210006900148300001000217490000700227520167000234653001701904653001001921653001001931653001601941653001701957653001101974100001801985700001702003700001702020700001802037700002102055856005702076 2015 eng d00aThe Stream Biome Gradient Concept: factors controlling lotic systems across broad biogeographic scales0 aStream Biome Gradient Concept factors controlling lotic systems  a1 -190 v343 a

We propose the Stream Biome Gradient Concept as a way to predict macroscale biological patterns in streams. This concept is based on the hypothesis that many abiotic and biotic features of streams change predictably along climate (temperature and precipitation) gradients because of direct influences of climate on hydrology, geomorphology, and interactions mediated by terrestrial vegetation. The Stream Biome Gradient Concept generates testable hypotheses related to continental variation among streams worldwide and allows aquatic scientists to understand how results from one biome might apply to a less-studied biome. Some predicted factors change monotonically across the biome/climate gradients, whereas others have maxima or minima in the central portion of the gradient. For example, predictions across the gradient from drier deserts through grasslands to wetter forests include more permanent flow, less bare ground, lower erosion and sediment transport rates, decreased importance of autochthonous C inputs to food webs, and greater stream animal species richness. In contrast, effects of large ungulate grazers on streams are expected to be greater in grasslands than in forests or deserts, and fire is expected to have weaker effects in grassland streams than in desert and forest streams along biome gradients with changing precipitation and constant latitude or elevation. Understanding historic patterns among biomes can help describe the evolutionary template at relevant biogeographic scales, can be used to broaden other conceptual models of stream ecology, and could lead to better management and conservation across the broadest scales.

10abiogeography10abiome10alotic10amacro-scale10amacrosystems10astream1 aDodds, W., K.1 aGido, K., B.1 aWhiles, M.R.1 aDaniels, M.D.1 aGrudzinski, B.P. uhttps://www.journals.uchicago.edu/doi/10.1086/67975602188nas a2200217 4500008004100000245015900041210006900200260001600269300001100285490000700296520142400303653002601727653002301753653002701776653002201803653002301825100001601848700001801864700001801882856007001900 2015 eng d00aWoody plant encroachment, and its removal, impact bacterial and fungal communities across stream and terrestrial habitats in a tallgrass prairie ecosystem0 aWoody plant encroachment and its removal impact bacterial and fu cDec-10-2015 afiv1090 v913 aWoody plant encroachment has become a global threat to grasslands and has caused declines in aboveground richness and changes in ecosystem function; yet we have a limited understanding on the effects of these phenomena on belowground microbial communities. We completed riparian woody plant removals at Konza Prairie Biological Station, Kansas and collected soils spanning land–water interfaces in removal and woody vegetation impacted areas. We measured stream sediments and soils for edaphic variables (C and N pools, soil water content, pH) and bacterial (16S rRNA genes) and fungal (ITS2 rRNA gene repeat) communities using Illumina MiSeq metabarcoding. Bacterial richness and diversity decreased with distance from streams. Fungal richness decreased with distance from the stream in wooded areas, but was similar across landscape position while Planctomycetes and Basidiomycota relative abundance was lower in removal areas. Cyanobacteria, Ascomycota, Chytridiomycota and Glomeromycota relative abundance was greater in removal areas. Ordination analyses indicated that bacterial community composition shifted more across land–water interfaces than fungi yet both were marginally influenced by treatment. This study highlights the impacts of woody encroachment restoration on grassland bacterial and fungal communities which likely subsequently affects belowground processes and plant health in this ecosystem.10abacterial communities10afungal communities10aland–water interface10atallgrass prairie10awoody encroachment1 aVeach, A.M.1 aDodds, W., K.1 aJumpponen, A. uhttp://femsec.oxfordjournals.org/lookup/doi/10.1093/femsec/fiv10902542nas a2200229 4500008004100000245009900041210006900140490001400209520182600223653001202049653002302061653002102084653001402105653001002119653002002129653002502149653001002174100001602184700001802200700001602218856007802234 2014 eng d00aFire and grazing influences on rates of riparian woody plant expansion along grassland streams0 aFire and grazing influences on rates of riparian woody plant exp0 v9:e1069223 a

Grasslands are threatened globally due to the expansion of woody plants. The few remaining headwater streams within tallgrass prairies are becoming more like typical forested streams due to rapid conversion of riparian zones from grassy to wooded. Forestation can alter stream hydrology and biogeochemistry. We estimated the rate of riparian woody plant expansion within a 30 m buffer zone surrounding the stream bed across whole watersheds at Konza Prairie Biological Station over 25 years from aerial photographs. Watersheds varied with respect to experimentally-controlled fire and bison grazing. Fire frequency, presence or absence of grazing bison, and the historical presence of woody vegetation prior to the study time period (a proxy for proximity of propagule sources) were used as independent variables to predict the rate of riparian woody plant expansion between 1985 and 2010. Water yield was estimated across these years for a subset of watersheds. Riparian woody encroachment rates increased as burning became less frequent than every two years. However, a higher fire frequency (1–2 years) did not reverse riparian woody encroachment regardless of whether woody vegetation was present or not before burning regimes were initiated. Although riparian woody vegetation cover increased over time, annual total precipitation and average annual temperature were variable. So, water yield over 4 watersheds under differing burn frequencies was quite variable and with no statistically significant detected temporal trends. Overall, burning regimes with a frequency of every 1–2 years will slow the conversion of tallgrass prairie stream ecosystems to forested ones, yet over long time periods, riparian woody plant encroachment may not be prevented by fire alone, regardless of fire frequency.

10aAnthrax10aBacillus anthracis10aBacterial spores10aCytokines10aEdema10aImmune response10aInnate immune system10aLungs1 aVeach, A.M.1 aDodds, W., K.1 aSkibbee, A. uhttps://journals.plos.org/plosone/article?id=10.1371/journal.pone.010692203192nas a2200145 4500008004100000245008400041210006900125260004300194490002200237520259200259653005002851100001902901700001802920856010802938 2014 eng d00aThe influence of fire and grazing on tallgrass prairie streams and herpetofauna0 ainfluence of fire and grazing on tallgrass prairie streams and h aManhattan, KSbKansas State University0 vPhD. Dissertation3 a

Tallgrass prairie evolved with fire-grazer interactions. Fire and grazing are vital processes for maintaining grasslands and cattle production, and therefore will be continued as land management schemes. The effects of fire and grazers on prairie streams are understudied, but may significantly influence stream ecology. This dissertation examined how prescribed burning, bison grazing, and patch-burn grazing (by cattle) influence water quality, stream biota, and riparian amphibians and reptiles at Konza Prairie, Kansas, or Osage Prairie, Missouri. Using Global Positioning System, we monitored bison and cattle distribution throughout watersheds. The immediate effects of prescribed burning were examined at both Konza and Osage Prairies. The impacts of bison on water quality were determined by using a long-term dataset from Konza Prairie and compared watersheds with and without bison. Amphibian and reptile assemblages were monitored for two years at Osage, and assemblage data were analyzed using redundancy analysis, permuted analysis of variance, and occupancy modeling. A patch-burn grazing experiment occurred for 5 years at Osage (2 years pretreatment data and 3 years of treatments) and was analyzed using a before-after, control-impact design. Prescribed burning had minimal effects on water chemistry. At Konza Prairie, bison did not alter water quality likely because they spent negligible time (<5%) in streams. Contrarily, cattle at Osage Prairie significantly increased stream concentrations of total suspended solids, nutrients, Escherichia coli bacteria, algal biomass, and primary production. Unlike bison, cattle spent significant time (~21%) in streams if allowed access to riparian zones. In watersheds with cattle excluded from streams by riparian fencing, water quality contaminant concentrations increased significantly, but not to the magnitude of unfenced streams. Amphibian abundance and richness were not different among patch types; instead, they were restricted to specific basins. However, reptiles displayed preference for certain patch-types, and had the highest abundance and richness in watersheds with fire and grazing. These results have implications for natural resource management. Riparian fencing of cattle may be a useful practice in areas where water resource protection is the priority. However, overland flow may alter water quality in watersheds with grazers despite fencing. Land managers will need to define management objectives and accept trade-offs in water quality, amphibian and reptile habitat, and cattle production.

10aCattle; Bison; Amphibian; Reptile; Grasslands1 aLarson, D., M.1 aDodds, W., K. uhttp://krex.k-state.edu/dspace/bitstream/handle/2097/17560/DanelleLarson2014.pdf?sequence=7&isAllowed=y02431nas a2200373 4500008004100000245012200041210006900163300001500232490000700247520133300254100001801587700002401605700001901629700001501648700001601663700001801679700001601697700001701713700001801730700001901748700001901767700001301786700001901799700001701818700002101835700001801856700001801874700002001892700001401912700002401926700001901950700001401969856007401983 2014 eng d00aYou are not always what we think you eat: selective assimilation across multiple whole-stream isotopic tracer studies0 aYou are not always what we think you eat selective assimilation  a2757 -27670 v953 a

Analyses of 21 15N stable isotope tracer experiments, designed to examine food web dynamics in streams around the world, indicated that the isotopic composition of food resources assimilated by primary consumers (mostly invertebrates) poorly reflected the presumed food sources. Modeling indicated that consumers assimilated only 33–50% of the N available in sampled food sources such as decomposing leaves, epilithon, and fine particulate detritus over feeding periods of weeks or more. Thus, common methods of sampling food sources consumed by animals in streams do not sufficiently reflect the pool of N they assimilate. Isotope tracer studies, combined with modeling and food separation techniques, can improve estimation of N pools in food sources that are assimilated by consumers. Food web studies that use putative food samples composed of actively cycling (more readily assimilable) and refractory (less assimilable) N fractions may draw erroneous conclusions about diets, N turnover, and trophic linkages of consumers. By extension, food web studies using stoichiometric or natural abundance approaches that rely on an accurate description of food-source composition could result in errors when an actively cycling pool that is only a fraction of the N pool in sampled food resources is not accounted for.

1 aDodds, W., K.1 aCollins, Scott., L.1 aHamilton, S.K.1 aTank, J.L.1 aJohnson, S.1 aWebster, J.R.1 aSimon, K.S.1 aWhiles, M.R.1 aRantala, H.M.1 aMcDowell, W.H.1 aPeterson, S.D.1 aRiis, T.1 aCrenshaw, C.L.1 aThomas, S.A.1 aKristensen, P.B.1 aCheever, B.M.1 aFlecker, A.S.1 aGriffiths, N.A.1 aCrowl, T.1 aRosi-Marshall, E.J.1 aEl-Sabaawi, R.1 aMarti, E. uhttps://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/13-2276.102394nas a2200313 4500008004100000245009600041210006900137300001300206490000700219520149500226653001601721653001401737653001201751653001501763653001201778653002001790653001201810653002201822653001901844653002101863653002701884100001701911700002101928700001801949700001801967700001701985700001902002856005902021 2013 eng d00aBlazing and grazing: influences of fire and bison on tallgrass prairie stream water quality0 aBlazing and grazing influences of fire and bison on tallgrass pr a779 -7910 v323 a

Fire and grazers (such as Bison bison) were historically among the most important agents for maintaining and managing tallgrass prairie, but we know little about their influences on water-quality dynamics in streams. We analyzed 2 y of data on total suspended solids (TSS), total N (TN), and total P (TP) (3 samples per week per stream during flow) in 3 prairie streams with fire and bison grazing treatments at Konza Prairie Biological Station, Kansas (USA), to assess whether fire and bison increase the concentrations of these water-quality variables. We quantified the spatial and temporal locations of bison (∼0.21 animal units/ha) with Global Positioning System collars and documented bison trails, paw patches, wallows, and naturally exposed sediment patches within riparian buffers. Three weeks post-fire, TN and TP decreased (t-test, p < 0.001), but TSS did not change. Bison spent <6% of their time within 10 m of the streams, increased the amount of exposed sediment in the riparian areas, and avoided wooded mainstem branches of stream (χ2 test, p < 0.001). Temporal trends suggest that low discharge or increased bison density in the stream may increase TSS and TP during the summer months. Our results indicate a weak connection between TSS and nutrients with bison access to streams over our 2-y study and indicate that low TSS and nutrients characterize tallgrass prairie streams with fire and moderate bison densities relative to surrounding land uses.

10aBison bison10aBos bison10aburning10aGrasslands10agrazers10aprescribed fire10astreams10atallgrass prairie10atotal nitrogen10atotal phosphorus10atotal suspended solids1 aLarson, D.M.1 aGrudzinski, B.P.1 aDodds, W., K.1 aDaniels, M.D.1 aSkibbe, A.M.1 aJoern, Anthony uhttps://www.journals.uchicago.edu/doi/10.1899/12-118.102161nas a2200229 4500008004100000245009200041210006900133300001500202490000700217520143700224653000901661653002701670653002901697653001901726653002201745653001801767100001301785700001801798700001801816700001401834856008301848 2013 eng d00aDissolved black carbon in grassland streams: is there an effect of recent fire history?0 aDissolved black carbon in grassland streams is there an effect o a2557 -25620 v903 a

While the existence of black carbon as part of dissolved organic matter (DOM) has been confirmed, quantitative determinations of dissolved black carbon (DBC) in freshwater ecosystem and information on factors controlling its concentration are scarce. In this study, stream surface water samples from a series of watersheds subject to different burn frequencies in Konza Prairie (Kansas, USA) were collected in order to determine if recent fire history has a noticeable effect on DBC concentration. The DBC levels detected ranged from 0.04 to 0.11 mg L−1, accounting for ca. 3.32 ± 0.51% of dissolved organic carbon (DOC). No correlation was found between DBC concentration and neither fire frequency nor time since last burn. We suggest that limited DBC flux is related to high burning efficiency, possibly greater export during periods of high discharge and/or the continuous export of DBC over long time scales. A linear correlation between DOC and DBC concentrations was observed, suggesting the export mechanisms determining DOC and DBC concentrations are likely coupled. The potential influence of fire history was less than the influence of other factors controlling the DOC and DBC dynamics in this ecosystem. Assuming similar conditions and processes apply in grasslands elsewhere, extrapolation to a global scale would suggest a global grasslands flux of DBC on the order of 0.14 Mt carbon year−1.

10aBPCA10aDissolved black carbon10aDissolved organic carbon10aFire frequency10aGrassland streams10aKonza Prairie1 aDing, Y.1 aYamashita, Y.1 aDodds, W., K.1 aJaffe, R. uhttps://www.sciencedirect.com/science/article/pii/S0045653512013604?via%3Dihub02265nas a2200169 4500008004100000245007800041210006900119300001300188490000700201520172700208100001701935700001801952700001801970700001701988700001802005856007202023 2013 eng d00aEcosystem characteristics of remnant, headwater tallgrass prairie streams0 aEcosystem characteristics of remnant headwater tallgrass prairie a239 -2490 v423 a

North America has lost >95% of its native tallgrass prairie due to land conversion, making prairie streams one of the most endangered ecosystems. Research on the basic ecosystem characteristics of the remaining natural prairie streams will inform conservation and management. We examined the structure and function of headwater streams draining tallgrass prairie tracts at Osage Prairie in Missouri and the Konza Prairie Biological Station in Kansas and compared those values with literature values for streams draining agricultural watersheds in the region. We quantified physicochemical and biological characteristics for 2 yr. Streams at Osage and Konza were characterized by low nutrients and low suspended sediments (substantially lower than impacted sites in the region), slight heterotrophic status, and high temporal variability. Suspended sediments and nutrient concentrations were generally low in all prairie streams, but storms increased concentrations of both by 3- to 12-fold. Spring prescribed burns were followed by a slight increase in chlorophyll a and decreased nutrients, potentially due to greater light availability. Benthic macroinvertebrate communities at Osage showed seasonal patterns that were probably linked to variable hydrology. We found nine amphibian species using the Osage streams as habitat or breeding sites, but little usage at Konza was probably due to dry conditions and low discharge. Our study indicates that two remnant tallgrass prairie streams along a longitudinal gradient are fairly similar in terms of physicochemical features and have good water quality relative to agricultural watersheds but can differ considerably in macroinvertebrate and amphibian abundance.

1 aLarson, D.M.1 aDodds, W., K.1 aJackson, K.E.1 aWhiles, M.R.1 aWinders, K.R. uhttps://dl.sciencesocieties.org/publications/jeq/abstracts/42/1/23902680nas a2200229 4500008004100000245009800041210006900139300001300208490000700221520195100228653002002179653002102199653002002220653002402240653002202264653002302286100002002309700002002329700001702349700001802366856006602384 2013 eng d00aWoody vegetation removal stimulates riparian and benthic denitrification in tallgrass prairie0 aWoody vegetation removal stimulates riparian and benthic denitri a547 -5600 v163 a

Expansion of woody vegetation into areas that were historically grass-dominated is a significant contemporary threat to grasslands, including native tallgrass prairie ecosystems of the Midwestern United States. In tallgrass prairie, much of this woody expansion is concentrated in riparian zones with potential impacts on biogeochemical processes there. Although the effects of woody riparian vegetation on denitrification in both riparian soils and streams have been well studied in naturally wooded ecosystems, less is known about the impacts of woody vegetation encroachment in ecosystems that were historically dominated by herbaceous vegetation. Here, we analyze the effect of afforestation and subsequent woody plant removal on riparian and benthic denitrification. Denitrification rates in riparian soil and selected benthic compartments were measured seasonally in naturally grass-dominated riparian zones, woody encroached riparian zones, and riparian zones with woody vegetation removed in two separate watersheds. Riparian soil denitrification was highly seasonal, with the greatest rates in early spring. Benthic denitrification also exhibited high temporal variability, but no seasonality. Soil denitrification rates were greatest in riparian zones where woody vegetation was removed. Additionally, concentrations of nitrate, carbon, and soil moisture (indicative of potential anoxia) were greatest in wood removal soils. Differences in the presence and abundance of benthic compartments reflected riparian vegetation, and may have indirectly affected denitrification in streams. Riparian soil denitrification increased with soil water content and NO3 −. Management of tallgrass prairies that includes removal of woody vegetation encroaching on riparian areas may alter biogeochemical cycling by increasing nitrogen removed via denitrification while the restored riparian zones return to a natural grass-dominated state.

10adenitrification10anitrogen removal10aprairie streams10ariparian vegetation10atallgrass prairie10awoody encroachment1 aReisinger, A.J.1 aBlair, John, M.1 aRice, C., W.1 aDodds, W., K. uhttps://link.springer.com/article/10.1007%2Fs10021-012-9630-302957nas a2200241 4500008004100000245011800041210006900159300001200228490000700240520219800247100001502445700001802460700001302478700001702491700001602508700001802524700001602542700001502558700002202573700002002595700001702615856008302632 2012 eng d00aDissolved organic matter in headwater streams: compositional variability across climatic regions of North America0 aDissolved organic matter in headwater streams compositional vari a95 -1080 v943 a

Dissolved organic matter (DOM) represents the largest organic matter pool in freshwater systems, but much of it remains molecularly uncharacterized. Although freshwater systems cover only a small area of the earth’s surface, inland waters are an important component of the global carbon cycle. The traditional idea that rivers are simply conduits for refractory carbon delivery to coastal areas is inconsistent with carbon flux estimates, and streams have been shown to serve as reactors for DOM cycling. The overall quality of DOM, and its associated reactivity, can be related to its chemical composition and molecular structure. However, the variability of DOM composition in freshwater ecosystems, particularly in headwater streams, is poorly characterized. Detailed molecular studies of DOM from small streams across climatic regions, which could provide critical information regarding carbon dynamics on a more global scale, have not been performed. To address these issues, this study applies a multi-method analytical approach in an attempt to assess molecular characteristics of DOM and ultrafiltered DOM (UDOM) in headwater streams from different climatic regions in North America. In general terms the chemical and molecular characteristics of UDOM from six different biomes were determined in unsurpassed detail to feature some clear general similarities but also specific differences. While the degree of similarity is remarkable, and suggests similar source strengths, such as soil-derived organic matter and/or similar diagenetic degradation processes for DOM from vastly different environments, each sample was clearly unique in its overall composition, featuring some distinct molecular patterns for at least one or more of the analytical determinations. Molecular and compositional differences of DOM from headwater streams should result from variations in DOM sources and localized environmental conditions, and consequently feature different photo- and bio-reactivity and associated re-mineralization potentials during fluvial transport. Such knowledge could assist in predicting the consequences of global change and its relationship to global carbon cycling.

1 aJaffé, R.1 aYamashita, Y.1 aMaie, N.1 aCooper, W.T.1 aDittmar, T.1 aDodds, W., K.1 aJones, J.B.1 aMyoshi, T.1 aOrtiz-Zayas, J.R.1 aPodgorski, D.C.1 aWatanabe, A. uhttps://www.sciencedirect.com/science/article/pii/S0016703712004097?via%3Dihub02686nas a2200133 4500008004100000245012800041210006900169300001500238490000700253520218100260100001602441700001802457856007702475 2012 eng d00aThe expansion of woody riparian vegetation, and subsequent stream restoration, influences the metabolism of prairie streams0 aexpansion of woody riparian vegetation and subsequent stream res a1138 -11500 v573 a

1. Tallgrass prairies and their streams are highly endangered ecosystems, and many remaining streams are threatened by the encroachment of woody riparian vegetation. An increase in riparian vegetation converts the naturally open-canopy prairie streams to closed-canopy systems. The effects of a change in canopy cover on stream metabolism are unknown. 2. Our goal was to determine the effects of canopy cover on prairie stream metabolism during a 4-year period in Kings Creek, KS, U.S.A. Metabolic rates from forested reaches were compared to rates in naturally open-canopy reaches and restoration reaches, the latter having closed canopies in 2006 and 2007 and open canopies in 2008 and 2009. Whole-stream metabolism was estimated using the two-station diurnal method. Chlorophyll a concentrations and mass of filamentous algae were measured after riparian removal to assess potential differences in algal biomass between reaches with open or closed canopies. 3. Metabolic rates were spatially and temporally variable even though the sites were on very similar streams or adjacent to each other within streams. Before riparian vegetation removal, whole-stream community respiration (CR) and net ecosystem production were greater with greater canopy cover. In the vegetation removal reaches, gross primary production was slightly greater after removal. 4. Chlorophyll a concentrations were marginally significantly greater in open (naturally open and removal reaches) than in closed canopy and differed significantly between seasons. Filamentous algal biomass was greater in open than in closed-canopy reaches. 5. Overall, the restoration allowed recovery of some features of open-canopy prairie streams. Woody expansion apparently increases CR and moves prairie stream metabolism towards a more net heterotrophic state. An increase in canopy cover decreases benthic chlorophyll, decreases dominance of filamentous algae and potentially alters resources available to the stream food web. The results of this study provide insights for land managers and conservationists interested in preserving prairie streams in their native open-canopy state

1 aRiley, A.J.1 aDodds, W., K. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2427.2012.02778.x02035nas a2200313 4500008004100000245007500041210006900116300001300185490000700198520118800205653000901393653001501402653001001417653001401427653001201441100001801453700001901471700001701490700001901507700001501526700001601541700001601557700001801573700001801591700001301609700001601622700001901638856006401657 2012 eng d00aSurprises and insights from long-term aquatic datasets and experiments0 aSurprises and insights from longterm aquatic datasets and experi a709 -7210 v623 a

Long-term research on freshwater ecosystems provides insights that can be difficult to obtain from other approaches. Widespread monitoring of ecologically relevant water-quality parameters spanning decades can facilitate important tests of ecological principles. Unique long-term data sets and analytical tools are increasingly available, allowing for powerful and synthetic analyses across sites. Long-term measurements or experiments in aquatic systems can catch rare events, changes in highly variable systems, time-lagged responses, cumulative effects of stressors, and biotic responses that encompass multiple generations. Data are available from formal networks, local to international agencies, private organizations, various institutions, and paleontological and historic records; brief literature surveys suggest much existing data are not synthesized. Ecological sciences will benefit from careful maintenance and analyses of existing long-term programs, and subsequent insights can aid in the design of effective future long-term experimental and observational efforts. Long-term research on freshwaters is particularly important because of their value to humanity.

10adata10afreshwater10alakes10along term10astreams1 aDodds, W., K.1 aRobinson, C.T.1 aGaiser, E.E.1 aHansen, G.J.A.1 aPowell, H.1 aSmith, J.M.1 aMorse, N.B.1 aJohnson, S.L.1 aGregory, S.V.1 aBell, T.1 aKratz, T.K.1 aMcDowell, W.H. uhttps://academic.oup.com/bioscience/article/62/8/709/24421402874nas a2200325 4500008004100000245007600041210006900117300001300186490000800199520193800207653001602145653005802161653000802219653002002227653001102247653002302258100002002281700002102301700001702322700001302339700001502352700001702367700001702384700001802401700001402419700001902433700001502452700001502467856006602482 2011 eng d00aCross-stream comparison of substrate-specific denitrification potential0 aCrossstream comparison of substratespecific denitrification pote a381 -3920 v1043 a

Headwater streams have a demonstrated ability to denitrify a portion of their nitrate (NO3 −) load but there has not been an extensive consideration of where in a stream this process is occurring and how various habitats contribute to total denitrification capability. As part of the Lotic Intersite Nitrogen Experiment II (LINX II) we measured denitrification potential in 65 streams spanning eight regions of the US and draining three land-use types. In each stream, potential denitrification rates were measured in common substrate types found across many streams as well as locations unique to particular streams. Overall, habitats from streams draining urban and agricultural land-uses showed higher potential rates of denitrification than reference streams draining native vegetation. This difference among streams was probably driven by higher ambient nitrate concentrations found in urban or agricultural streams. Within streams, sandy habitats and accumulations of fine benthic organic matter contributed more than half of the total denitrification capacity (mg N removed m−2 h−1). A particular rate of potential denitrification per unit area could be achieved either by high activity per unit organic matter or lower activities associated with larger standing stocks of organic matter. We found that both small patches with high rates (hot spots) or more widespread but less active areas (cool matrix) contributed significantly to whole stream denitrification capacity. Denitrification estimated from scaled-up denitrification enzyme assay (DEA) potentials were not always dramatically higher than in situ rates of denitrification measured as 15N gas generation following 24-h 15N–NO3 tracer additions. In general, headwater streams draining varying land-use types have significant potential to remove nitrate via denitrification and some appear to be functioning near their maximal capacity.

10aComparative10aComparison of potential with realized denitrification10aDEA10adenitrification10astream10aSubstrate-specific1 aFindlay, S.E.G.1 aMulholland, P.J.1 aHamilton, S.1 aTank, J.1 aBernot, M.1 aBurgin, A.J.1 aCrenshaw, C.1 aDodds, W., K.1 aGrimm, N.1 aMcDowell, W.H.1 aPotter, J.1 aSobota, D. uhttps://link.springer.com/article/10.1007%2Fs10533-010-9512-802357nas a2200253 4500008004100000245016000041210006900201300001300270490000700283520155600290653001501846653002001861653002301881653001001904653001101914653001301925653002001938653001301958100002001971700001801991700001702009700001802026856005902044 2011 eng d00aDirect and indirect effects of central stoneroller (Campostoma anomalum) on mesocosm recovery following a flood: can macroconsumers affect denitrification?0 aDirect and indirect effects of central stoneroller Campostoma an a840 -8520 v303 a

Anthropogenic N loadings and perturbations of macroconsumer communities impair ecological and economic services provided by streams. Organisms are adapted to natural disturbances, such as flooding and desiccation, but how anthropogenic and natural disturbances interact is poorly understood. We used large outdoor mesocosms to study the effect of Campostoma anomalum, a common prairie headwater-stream minnow, and NH4+ additions (to simulate fish excretion) on the recovery of ecosystem structure and function following a flood, highlighting the potential for Campostoma (and other macroconsumers) to affect denitrification. Campostoma and NH4+ treatments differentially affected particulate organic matter size and filamentous algal structure. Ecosystem structure responded differently to mesocosm treatment over time, a result suggesting that grazers or NH4+-N availability may be especially important during early recovery periods. The presence of Campostoma did not influence denitrification, but NH4+ additions altered the response of denitrifiers to nutrient and energy amendments, and denitrification rates decreased following the recovery of mesocosms. Temporal changes in denitrification probably were caused by increasing hyporheic dissolved O2 concentrations, which led to potentially fewer anoxic microsites for production of denitrification enzymes. Our study shows that grazers affect the recovery of ecosystem structure, but denitrification in the context of these prairie-stream mesocosms appears to be unaffected by Campostoma.

10aCampostoma10adenitrification10aEcosystem function10aFlood10agrazer10amesocosm10aprairie streams10arecovery1 aReisinger, A.J.1 aPresuma, D.L.1 aGido, K., B.1 aDodds, W., K. uhttps://www.journals.uchicago.edu/doi/10.1899/10-169.100499nas a2200145 4500008004100000245009400041210006900135300001300204490000700217100001800224700001800242700001700260700001700277856005900294 2011 eng d00aDynamic influences of nutrients and grazing fish on periphyton during recovery from flood0 aDynamic influences of nutrients and grazing fish on periphyton d a331 -3450 v301 aMurdock, J.N.1 aDodds, W., K.1 aGido, K., B.1 aWhiles, M.R. uhttps://www.journals.uchicago.edu/doi/10.1899/10-039.102970nas a2200169 4500008004100000245013600041210006900177260004300246490002100289520238200310653001102692653001502703653001202718100001602730700001802746856003602764 2011 eng d00aEffects of riparian woody vegetation encroachment on prairie stream structure and function with emphasis on whole-stream metabolism0 aEffects of riparian woody vegetation encroachment on prairie str aManhattan, KSbKansas State University0 vPhD Dissertation3 a

Much of the North American tallgrass prairie ecosystem has been converted to cropland or urbanized. One threat to the remaining prairie ecosystems, and the streams within, is woody vegetation encroachment. Stream productivity, measured as metabolism, is a fundamental process comprised of gross primary production (GPP) and (CR) community respiration. Understanding GPP and CR is important because these processes are vital to ecosystem function and can be impacted by a change in canopy cover. First, I investigated improvements in existing methods for estimating whole-stream metabolism as estimated from diel patterns of oxygen (O2). I compared measured and modeled O2 and aeration (a physical parameter required for measurement of metabolism) rates to determine if direct measurement of aeration is necessary and the importance of temperature correction of metabolism. Modeling was moderately successful in determining aeration rates, and temperature correction of GPP and CR substantially improved model fits. Second, effects of woody vegetation encroachment on prairie stream function were investigated. Stream metabolism was measured for four years in duplicate reaches with varying canopy cover (closed canopy, naturally open canopy, and vegetation removal reaches). The removal reaches had closed canopy for the first two years and open canopy for the last two years. Canopy cover increased CR rates and had minimal effects on GPP. Third, the same experiment was used to determine the effects of woody vegetation encroachment on prairie stream ecosystem structure and food web interactions. Chlorophyll a and filamentous algal biomass were greater in naturally open and vegetation removal reaches, although the effects were stronger on filamentous algal biomass. As canopy cover decreased, the filamentous algal biomass to chlorophyll ratio increased, indicating a shift in algal community structure. Stable isotope analysis indicated some shift in pathways of nitrogen and carbon flux into the food web related to degree of canopy cover, but overlap in the signature of food sources made distinct food sources difficult to identify. The data indicate that riparian encroachment can influence ecosystem structure and function in prairie streams and restoration to remove woody riparian cover may restore some ecosystem features of naturally open canopy streams.

10acanopy10ametabolism10astreams1 aRiley, A.J.1 aDodds, W., K. uhttp://hdl.handle.net/2097/854506005nas a2200433 4500008004100000245007700041210006900118300001300187490000800200520484900208100001905057700001505076700001905091700001905110700001505129700002105144700001905165700001905184700001705203700001505220700001805235700001605253700001805269700001905287700001605306700001705322700001705339700001705356700001705373700001705390700001705407700001605424700001805440700001705458700001905475700001705494700001705511856004305528 2011 eng d00aNitrous oxide emission from denitrification in stream and river networks0 aNitrous oxide emission from denitrification in stream and river  a214 -2190 v1083 a

Nitrous oxide (N2O) is a potent greenhouse gas that contributes to climate change and stratospheric ozone destruction. Anthropogenic nitrogen (N) loading to river networks is a potentially important source of N2O via microbial denitrification that converts N to N2O and dinitrogen (N2). The fraction of denitrified N that escapes as N2O rather than N2 (i.e., the N2O yield) is an important determinant of how much N2O is produced by river networks, but little is known about the N2O yield in flowing waters. Here, we present the results of whole-stream 15N-tracer additions conducted in 72 headwater streams draining multiple land-use types across the United States. We found that stream denitrification produces N2O at rates that increase with stream water nitrate (NO3−) concentrations, but that <1% of denitrified N is converted to N2O. Unlike some previous studies, we found no relationship between the N2O yield and stream water NO3−. We suggest that increased stream NO3− loading stimulates denitrification and concomitant N2O production, but does not increase the N2O yield. In our study, most streams were sources of N2O to the atmosphere and the highest emission rates were observed in streams draining urban basins. Using a global river network model, we estimate that microbial N transformations (e.g., denitrification and nitrification) convert at least 0.68 Tg·y−1 of anthropogenic N inputs to N2O in river networks, equivalent to 10% of the global anthropogenic N2O emission rate. This estimate of stream and river N2O emissions is three times greater than estimated by the Intergovernmental Panel on Climate Change. Humans have more than doubled the availability of fixed nitrogen (N) in the biosphere, particularly through the production of N fertilizers and the cultivation of N-fixing crops (1). Increasing N availability is producing unintended environmental consequences including enhanced emissions of nitrous oxide (N2O), a potent greenhouse gas (2) and an important cause of stratospheric ozone destruction (3). The Intergovernmental Panel on Climate Change (IPCC) estimates that the microbial conversion of agriculturally derived N to N2O in soils and aquatic ecosystems is the largest source of anthropogenic N2O to the atmosphere (2). The production of N2O in agricultural soils has been the focus of intense investigation (i.e., >1,000 published studies) and is a relatively well constrained component of the N2O budget (4). However, emissions of anthropogenic N2O from streams, rivers, and estuaries have received much less attention and remain a major source of uncertainty in the global anthropogenic N2O budget. Microbial denitrification is a large source of N2O emissions in terrestrial and aquatic ecosystems. Most microbial denitrification is a form of anaerobic respiration in which nitrate (NO3−, the dominant form of inorganic N) is converted to dinitrogen (N2) and N2O gases (5). The proportion of denitrified NO3− that is converted to N2O rather than N2 (hereafter referred to as the N2O yield and expressed as the mole ratio) partially controls how much N2O is produced via denitrification (6), but few studies provide information on the N2O yield in streams and rivers because of the difficulty of measuring N2 and N2O production in these systems. Here we report rates of N2 and N2O production via denitrification measured using whole-stream 15NO3−-tracer experiments in 72 headwater streams draining different land-use types across the United States. This project, known as the second Lotic Intersite Nitrogen eXperiment (LINX II), provides unique whole-system measurements of the N2O yield in streams. Although N2O emission rates have been reported for streams and rivers (7, 8), the N2O yield has been studied mostly in lentic freshwater and marine ecosystems, where it generally ranges between 0.1 and 1.0%, although yields as high as 6% have been observed (9). These N2O yields are low compared with observations in soils (0–100%) (10), which may be a result of the relatively lower oxygen (O2) availability in the sediments of lakes and estuaries. However, dissolved O2 in headwater streams is commonly near atmospheric equilibrium and benthic algal biofilms can produce O2 at the sediment–water interface, resulting in strong redox gradients more akin to those in partially wetted soils. Thus, streams may have variable and often high N2O yields, similar to those in soils (11). The N2O yield in headwater streams is of particular interest because much of the NO3− input to rivers is derived from groundwater upwelling into headwater streams. Furthermore, headwater streams compose the majority of stream length within a drainage network and have high ratios of bioreactive benthic surface area to water volume (12).

1 aBeaulieu, J.K.1 aTank, J.L.1 aHamilton, S.K.1 aWollheim, W.M.1 aHall, R.O.1 aMulholland, P.J.1 aPeterson, B.J.1 aAshkenas, L.R.1 aCooper, L.W.1 aDahm, C.N.1 aDodds, W., K.1 aGrimm, N.B.1 aJohnson, S.L.1 aMcDowell, W.H.1 aPoole, G.C.1 aValett, H.M.1 aArango, C.P.1 aBernot, M.J.1 aBurgin, A.J.1 aCrenshaw, C.1 aHelton, A.M.1 aJohnson, L.1 aO'Brien, J.M.1 aPotter, J.D.1 aSheibley, R.W.1 aSobota, D.J.1 aThomas, S.M. uhttps://www.pnas.org/content/108/1/21402388nas a2200157 4500008004100000245012800041210006900169300001500238490000700253520182300260100001702083700001802100700001702118700001802135856007702153 2011 eng d00aNutrient loading and grazing by the minnow Phoxinus erythrogaster shift periphyton abundance and stoichiometry in mesocosms0 aNutrient loading and grazing by the minnow Phoxinus erythrogaste a1133 -11460 v563 a

1. Anthropogenic activities in prairie streams are increasing nutrient inputs and altering stream communities. Understanding the role of large consumers such as fish in regulating periphyton structure and nutritional content is necessary to predict how changing diversity will interact with nutrient enrichment to regulate stream nutrient processing and retention. 2. We characterised the importance of grazing fish on stream nutrient storage and cycling following a simulated flood under different nutrient regimes by crossing six nutrient concentrations with six densities of a grazing minnow (southern redbelly dace, Phoxinus erythrogaster) in large outdoor mesocosms. We measured the biomass and stoichiometry of overstory and understory periphyton layers, the stoichiometry of fish tissue and excretion, and compared fish diet composition with available algal assemblages in pools and riffles to evaluate whether fish were selectively foraging within or among habitats. 3. Model selection indicated nutrient loading and fish density were important to algal composition and periphyton carbon (C): nitrogen (N). Nutrient loading increased algal biomass, favoured diatom growth over green algae and decreased periphyton C : N. Increasing grazer density did not affect biomass and reduced the C : N of overstory, but not understory periphyton. Algal composition of dace diet was correlated with available algae, but there were proportionately more diatoms present in dace guts. We found no correlation between fish egestion/excretion nutrient ratios and nutrient loading or fish density despite varying N content of periphyton. 4. Large grazers and nutrient availability can have a spatially distinct influence at a microhabitat scale on the nutrient status of primary producers in streams.

1 aKohler, T.J.1 aMurdock, J.N.1 aGido, K., B.1 aDodds, W., K. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2427.2010.02557.x02203nas a2200385 4500008004100000245009000041210006900131300001300200490000600213520111200219100001701331700001601348700001601364700001901380700001901399700002101418700002001439700001901459700001701478700001901495700001701514700001801531700001801549700001701567700001901584700001801603700001901621700001701640700001501657700001701672700001701689700001801706700002201724856007101746 2011 eng d00aThinking outside the channel: modeling nitrogen cycling in networked river ecosystems0 aThinking outside the channel modeling nitrogen cycling in networ a229 -2380 v93 a

Agricultural and urban development alters nitrogen and other biogeochemical cycles in rivers worldwide. Because such biogeochemical processes cannot be measured empirically across whole river networks, simulation models are critical tools for understanding river-network biogeochemistry. However, limitations inherent in current models restrict our ability to simulate biogeochemical dynamics among diverse river networks. We illustrate these limitations using a river-network model to scale up in situ measures of nitrogen cycling in eight catchments spanning various geophysical and land-use conditions. Our model results provide evidence that catchment characteristics typically excluded from models may control river-network biogeochemistry. Based on our findings, we identify important components of a revised strategy for simulating biogeochemical dynamics in river networks, including approaches to modeling terrestrial–aquatic linkages, hydrologic exchanges between the channel, floodplain/riparian complex, and subsurface waters, and interactions between coupled biogeochemical cycles.

1 aHelton, A.M.1 aPoole, G.C.1 aMeyer, J.L.1 aWollheim, W.M.1 aPeterson, B.J.1 aMulholland, P.J.1 aBernhardt, E.S.1 aStanford, J.A.1 aArango, C.P.1 aAshkenas, L.R.1 aCooper, L.W.1 aDodds, W., K.1 aGregory, S.V.1 aO’Hall, R.1 aHamilton, S.K.1 aJohnson, S.L.1 aMcDowell, W.H.1 aPotter, J.D.1 aTank, J.L.1 aThomas, S.M.1 aValett, H.M.1 aWebster, J.R.1 aZeglin, Lydia, H. uhttps://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/08021102350nas a2200169 4500008004100000245011900041210006900160300001500229490000700244520176600251100001802017700001702035700001802052700001902070700001702089856007402106 2010 eng d00aConsumer return chronology alters recovery trajectory of stream ecosystem structure and function following drought0 aConsumer return chronology alters recovery trajectory of stream  a1048 -10620 v913 a

Consumers are increasingly being recognized as important drivers of ecological succession, yet it is still hard to predict the nature and direction of consumer effects in nonequilibrium environments. We used stream consumer exclosures and large outdoor mesocosms to study the impact of macroconsumers (i.e., fish and crayfish) on recovery of intermittent prairie streams after drying. In the stream, macroconsumers altered system recovery trajectory by decreasing algal and macroinvertebrate biomass, primary productivity, and benthic nutrient uptake rates. However, macroconsumer influence was transient, and differences between exclosures and controls disappeared after 35 days. Introducing and removing macroconsumers after 28 days resulted mainly in changes to macroinvertebrates. In mesocosms, a dominant consumer (the grazing minnow Phoxinus erythrogaster) reduced macroinvertebrate biomass but had little effect on algal assemblage structure and ecosystem rates during recovery. The weak effect of P. erythrogaster in mesocosms, in contrast to the strong consumer effect in the natural stream, suggests that both timing and diversity of returning consumers are important to their overall influence on stream recovery patterns. Although we found that consumers significantly altered ecosystem structure and function in a system experiencing rapid changes in abiotic and biotic factors following disturbance, consumer effects diminished over time and trajectories converged to similar states with respect to primary producers, in spite of differences in consumer colonization history. Thus, consumer impacts can be substantial in recovering ecosystems and are likely to be dependent on the disturbance regime and diversity of the consumer community.

1 aMurdock, J.M.1 aGido, K., B.1 aDodds, W., K.1 aBertrand, K.N.1 aWhiles, M.R. uhttps://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/08-2168.103055nas a2200157 4500008004100000245013200041210006900173300001300242520245800255100001702713700001902730700001802749700001802767700001702785856009502802 2010 eng d00aDisturbance mediated effects of stream fishes on ecosystem processes: concepts and results from highly variable prairie streams0 aDisturbance mediated effects of stream fishes on ecosystem proce a593 -6173 a

Stream fishes can have strong top-down and bottom-up effects on ecosystem processes. However, the dynamic nature of streams constrains our ability to generalize these effects across systems with different disturbance regimes and species composition. To evaluate the role of fishes following disturbance, we used a series of field and mesocosm experiments that quantified the influence of grazers and water column minnows on primary productivity, periphyton structure, organic matter pools, and invertebrate communities following either scouring floods or drying of prairie streams. Results from individual experiments revealed highly significant effects of fishes, but the direction or magnitude of effects varied among experiments. Meta-analyses across experiments indicated that grazers consistently reduced the relative amount of fine benthic organic matter (FBOM) and chironomid abundance within 2 weeks after disturbances. However, effect sizes (log response ratios) were heterogeneous across experiments for algal biomass and algal filament lengths measured more than 4 weeks after a disturbance and potentially associated with system productivity and grazer densities. A similar analysis of 3–4 experiments using water column minnows only found a consistent trend of decreasing FBOM in fish treatments relative to controls when measured less than 2 weeks after disturbances and increase in gross primary productivity measured more than 4 weeks after disturbance. These results, along with those of others, were used to develop a conceptual framework for predicting the potential role of fishes in streams following disturbances (flood and drying). Both theoretical and empirical research shows that recovery of stream ecosystem processes will depend on the resilience of autotrophic and heterotrophic communities following disturbance. Fish effects may vary among functional groups but are generally predicted to be greatest during early stages of succession when algal and invertebrate communities are less complex and their biomass is low relative to fish biomass. Our analysis underscores the context dependency of consumer effects on ecosystem structure and function in nonequilibrium conditions and suggests that factors regulating fish densities and colonization of algal and invertebrate taxa need to be evaluated to predict the consequences of biodiversity loss in streams with variable or human-modified disturbance regimes.

1 aGido, K., B.1 aBertrand, K.N.1 aMurdock, J.N.1 aDodds, W., K.1 aWhiles, M.R. uhttps://www.k-state.edu/fishecology/msreprints/Gido%20et%20al.2010%20AFSbook%20chapter.pdf02995nas a2200193 4500008004100000245011700041210006900158260004300227490001400270520238200284653001402666653001502680653001402695653001102709653001102720100001602731700001802747856003602765 2010 eng d00aEcosystem Processes of Prairie Streams and the Impact of Anthropogenic Alteration on Stream Ecological Integrity0 aEcosystem Processes of Prairie Streams and the Impact of Anthrop aManhattan, KSbKansas State University0 vMS Thesis3 a

orth America has lost more than 95% of the original tallgrass prairie because of heavy land conversion, making prairie streams some of the most endangered habitats in North America. In order to effectively manage aquatic systems and improve biotic integrity of prairie streams research is needed that assesses the ecosystem characteristics of natural systems and evaluates the influence of anthropogenic alteration. We described the ecosystem characteristics of six ephemeral headwater streams draining tallgrass prairie within the Osage Plains of southwest Missouri. NO-3-N among all sites ranged from 1.56-91.36 μg L-1, NH+4-N ranged from 5.27-228.23 μg L-1, soluble reactive phosphorus ranged from below detection (1.0 μg L-1) to 41.22 μg L-1, TN ranged from 113.82-882.89 μg L-1, and TP ranged from 8.18-158.5 μg L-1during baseflow conditions. TN:TP molar ratios ranged from 22:1 to 53:1 indicating possible P was limiting relative to N in some streams. TSS during baseflow conditions ranged from 0.27-31.80 mg L-1. Autotrophic and heterotrophic comparisons of our study sites and reference sites classified our study streams as oligo-, meso-, and eu-autotrophic (N= 1, 4, and 1, respectively) and oligo-, meso-, and eu-heterotrophic (N= 4, 1, and 1, respectively). This study suggests that good water quality and moderate heterotrophic condition, with greater GPP resulting from an open canopy, are common conditions of tallgrass prairie streams. We also investigated interactions between land use/land cover, discharge rate, hydrologic alteration, and in-stream total suspended solids concentration in 23 Kansas- Missouri streams. Most streams had break points in the TSS loading rates at discharge rates exceeded <25% of days. Our estimates showed that 88% of the total annual TSS load occurred during the 11% of days with the greatest discharge rates. Buffered streams with greater percentages of grass and/or forest riparian areas had lower breakpoint values (indicating greater discharge rates were required to transport solid particles) and lower regression intercepts, which correlated to lesser TSS concentrations relative to unbuffered streams during high discharge days. In addition, grass buffered streams had smaller flood peaks and slower rise rates and forest buffered streams had less frequent floods, which lead to less total TSS transport.

10aecosystem10ametabolism10anutrients10asolids10astream1 aWinders, K.1 aDodds, W., K. uhttp://hdl.handle.net/2097/684903104nas a2200205 4500008004100000245006700041210006700108260004300175490001400218520247600232653001702708653002002725653002302745653001302768653002002781653002302801100002002824700001802844856003602862 2010 eng d00aFactors affecting denitrification in headwater prairie streams0 aFactors affecting denitrification in headwater prairie streams aManhattan, KSbKansas State University0 vMS Thesis3 a

Human-induced stressors such as increased nitrogen (N) loadings, altered watershed land-use, and biodiversity losses are a few of the numerous threats to aquatic systems. Prairie streams experience natural disturbances, such as flooding and desiccation, which may alter responses to anthropogenic stressors. Denitrification, the dissimilatory reduction of NO3- to N gas (N2O or N2), is the only permanent form of N removal from terrestrial or aquatic ecosystems, and is important in mitigating N pollution to streams and downstream waters. Little is known about the relationships between denitrification and riparian prairie vegetation or large consumers. In the first chapter, I used outdoor mesocosms to determine the impact of a grazing minnow, Campostoma anomalum, on structural and functional responses of prairie streams to a simulated flood, focusing on denitrification. In terrestrial ecosystems, grazing can stimulate denitrification, but this has not been studied in streams. Ammonium (NH4+) enrichments, used to simulate fish excretion, alleviated N limitations on denitrification. Both fish and NH4+ affected algal biomass accrual, but only fish affected algal filament lengths and particulate organic matter. In a second experiment, I examined the impact of woody vegetation expansion, a primary threat to tallgrass prairie, on riparian and benthic denitrification. Expansion of woody vegetation in these grasslands is due primarily to altered fire regimes, which historically inhibited woody vegetation growth. To determine the effect of woody vegetation expansion on benthic and riparian denitrification, woody vegetation was removed from the riparian zone of a grazed and an ungrazed watershed. Both soil and benthic denitrification rates from this removal buffer were compared to rates in grassy or woody riparian zones. Riparian soil denitrification was highly seasonal, with greatest rates occurring during early spring, and rates being low throughout the remainder of the year. Benthic denitrification was also temporally variable but did not exhibit seasonal trends, suggesting benthic denitrification is driven by factors other than water temperature. Removal of woody vegetation stimulated soil and benthic denitrification rates over rates found in naturally vegetated riparian zones. Elevated N loadings will continue to affect aquatic ecosystems, and these effects may be exacerbated by biodiversity losses or changing riparian vegetation.

10aBiodiversity10adenitrification10aEcosystem recovery10anitrogen10aprairie streams10awoody encroachment1 aReisinger, A.J.1 aDodds, W., K. uhttp://hdl.handle.net/2097/427303829nas a2200493 4500008004100000245007100041210006900112300001500181490000700196520248100203100001702684700001702701700001502718700002102733700001802754700001802772700001502790700001902805700001702824700001502841700001802856700001602874700001902890700001802909700001902927700001602946700001702962700001602979700001702995700001703012700001903029700001703048700001703065700001703082700001603099700001603115700002303131700001803154700001703172700001903189700001703208700001503225856009503240 2010 eng d00aInter-regional comparison of land-use effects on stream metabolism0 aInterregional comparison of landuse effects on stream metabolism a1874 -18900 v553 a1. Rates of whole-system metabolism (production and respiration) are fundamental indicators of ecosystem structure and function. Although first-order, proximal controls are well understood, assessments of the interactions between proximal controls and distal controls, such as land use and geographic region, are lacking. Thus, the influence of land use on stream metabolism across geographic regions is unknown. Further, there is limited understanding of how land use may alter variability in ecosystem metabolism across regions. 2. Stream metabolism was measured in nine streams in each of eight regions (n = 72) across the United States and Puerto Rico. In each region, three streams were selected from a range of three land uses: agriculturally influenced, urban-influenced, and reference streams. Stream metabolism was estimated from diel changes in dissolved oxygen concentrations in each stream reach with correction for reaeration and groundwater input. 3. Gross primary production (GPP) was highest in regions with little riparian vegetation (sagebrush steppe in Wyoming, desert shrub in Arizona/New Mexico) and lowest in forested regions (North Carolina, Oregon). In contrast, ecosystem respiration (ER) varied both within and among regions. Reference streams had significantly lower rates of GPP than urban or agriculturally influenced streams. 4. GPP was positively correlated with photosynthetically active radiation and autotrophic biomass. Multiple regression models compared using Akaike’s information criterion (AIC) indicated GPP increased with water column ammonium and the fraction of the catchment in urban and reference land-use categories. Multiple regression models also identified velocity, temperature, nitrate, ammonium, dissolved organic carbon, GPP, coarse benthic organic matter, fine benthic organic matter and the fraction of all land-use categories in the catchment as regulators of ER. 5. Structural equation modelling indicated significant distal as well as proximal control pathways including a direct effect of land-use on GPP as well as SRP, DIN, and PAR effects on GPP; GPP effects on autotrophic biomass, organic matter, and ER; and organic matter effects on ER. 6. Overall, consideration of the data separated by land-use categories showed reduced inter-regional variability in rates of metabolism, indicating that the influence of agricultural and urban land use can obscure regional differences in stream metabolism.1 aBernot, M.J.1 aSobota, D.J.1 aHall, R.O.1 aMulholland, P.J.1 aDodds, W., K.1 aWebster, J.R.1 aTank, J.L.1 aAshkenas, L.R.1 aCooper, L.W.1 aDahm, C.N.1 aGregory, S.V.1 aGrimm, N.B.1 aHamilton, S.K.1 aJohnson, S.L.1 aMcDowell, W.H.1 aMeyer, J.L.1 aPeterson, B.1 aPoole, G.C.1 aValett, H.M.1 aArango, C.P.1 aBeaulieu, J.J.1 aBurgin, A.J.1 aCrenshaw, C.1 aHelton, A.M.1 aJohnson, L.1 aMerriam, J.1 aNiederlehner, B.R.1 aO'Brien, J.M.1 aPotter, J.D.1 aSheibley, R.W.1 aThomas, S.M.1 aWilson, K. uhttp://129.130.186.12/content/inter-regional-comparison-land-use-effects-stream-metabolism02890nas a2200217 4500008004100000245010800041210006900149300001300218490000700231520217900238653002602417653001402443653002102457653002802478653002702506653002802533100001702561700001802578700001702596856005902613 2010 eng d00aRetrospective analysis of fish community change during a half-century of landuse and streamflow changes0 aRetrospective analysis of fish community change during a halfcen a970 -9870 v293 a

Ecological thresholds that lead to alternative community states can be exceeded through gradual perturbation or as a result of sudden disturbance. Many Great Plains streams have experienced dramatic changes in their hydrologic regime resulting from water and landuse changes that began as early as 1880. These changes, combined with the presence of many invasive species, have substantially altered the fish communities in this area. We quantified temporal changes in fish communities in 3 large river basins in relation to putative anthropogenic stressors, including increased sediment supply derived from row-crop agriculture (beginning in 1880), habitat fragmentation caused by reservoir construction (beginning in the 1950s), and reduced discharge caused by groundwater withdrawal (beginning in the 1960s). We hypothesized that these abiotic regime shifts, coupled with species invasions, would shift the system from a fish community dominated by lotic (flowing water) species to one dominated by lentic (still water) species. Further, we predicted that the timing and intensity of community change would vary across basins that experienced different types and levels of stressors. Restructuring of fish communities across the 3 river basins was driven primarily by similar increases in lentic species, with only a few declines in several large-river species. Current fish communities in these basins share <50% of the species recorded in historic collections, and these differences were driven by species extirpations and invasions. The greatest levels of community divergence over time occurred in western Kansas basins that experienced the most intense groundwater withdrawals and fragmentation by reservoirs. An alarming result from this analysis was the recent (after 1991) expansion of several invasive species in the Arkansas and lower Kansas River basins and the decline or extirpation of several native species where flow regimes are less heavily altered. Accelerating changes in the biota and habitat identified by our retrospective analysis highlight potential complications for restoring the habitat and native fish communities to a previous state.

10abiotic homogenization10aHydrology10aInvasive species10apresence–absence data10aretrospective analysis10astreamflow modification1 aGido, K., B.1 aDodds, W., K.1 aEberle, M.E. uhttps://www.journals.uchicago.edu/doi/10.1899/09-116.101856nas a2200181 4500008004100000245009500041210006900136300001300205490000700218520128100225653002001506653001601526653001801542653001901560100001801579700001801597856005901615 2010 eng d00aSaturation of NO3- uptake in prairie streams as a function of acute and chronic N exposure0 aSaturation of NO3 uptake in prairie streams as a function of acu a627 -6350 v293 a

We conducted a series of stepwise NO3− additions to investigate the response of NO3− uptake to short-term (acute) changes in N concentration in 3 prairie streams. Observed NO3− uptake rates increased with short-term elevations in NO3− concentration and were consistent with linear and Michaelis–Menten kinetics models. We compiled these data with uptake rates from additional published studies to calculate robust estimates of N uptake kinetics for prairie streams. Half-saturation coefficients based on compiled data were 6.7 µg/L for NH4+ and 67 µg/L for NO3−-N. This difference in half-saturation coefficients suggests that NH4+ is more efficiently assimilated than NO3−, indicating a preference for NH4+ as an N source. Similarly, ambient concentrations of NH4+ and NO3− were less than their respective half-saturation coefficients, and aerial uptake rates were generally <5% of the maximum, suggesting severe limitation of N uptake at ambient conditions. The observed pattern of uptake kinetics suggests that physiological constraints limit biotic N uptake in these low-N streams and contrasts with the pattern of uptake observed in streams with chronically elevated ambient NO3− concentrations.

10aBiogeochemistry10aKings Creek10aKonza Prairie10anitrate uptake1 aO'Brien, J.M.1 aDodds, W., K. uhttps://www.journals.uchicago.edu/doi/10.1899/09-021.100524nas a2200157 4500008004100000245008600041210006900127300001300196490000700209100001800216700001900234700001700253700002200270700001500292856005900307 2010 eng d00aThresholds, breakpoints, and nonlinearity in freshwaters as related to management0 aThresholds breakpoints and nonlinearity in freshwaters as relate a988 -9970 v291 aDodds, W., K.1 aClements, W.H.1 aGido, K., B.1 aHilderbrand, R.H.1 aKing, R.S. uhttps://www.journals.uchicago.edu/doi/10.1899/09-148.102477nas a2200193 4500008004100000245007300041210006900114300001100183490000800194520189600202653002102098653001402119653002302133653001102156653001502167100001702182700001802199856006602217 2009 eng d00aCentimeter-scale stream substratum heterogeneity and metabolic rates0 aCentimeterscale stream substratum heterogeneity and metabolic ra a53 -620 v6233 a

Spatial heterogeneity of substrata in streams may influence dissolved oxygen (O2) transport and nutrient forms. We studied the relationship between scales of substratum heterogeneity and O2. Heterogeneous systems could have greater respiration rates as a result of increased interfacial surfaces in the biogeochemically active areas between oxic and anoxic zones. We used grids with twelve 7 × 3.5 cm cells; half the cells were filled with sand and the other half with gravel to quantify the effect of centimeter-scale heterogeneity on respiration. The sand and gravel cells were arranged within the grids to give low, medium, and high heterogeneity. Grids were incubated for 15–17 days in a prairie stream, and then whole grid respiration was analyzed in closed recirculating chambers. Depth to anoxia and substratum metabolism were calculated from O2 microelectrode profiles measured in each cell of the grid and compared with data from natural stream transects from agricultural, urban, and prairie land use types. Shannon–Weaver (H′) diversity and “probability of change” indices were also used to compare heterogeneity of the grids to the natural stream transects. No significant differences were found among grid heterogeneity levels for respiration rate, but the anoxic interface was deeper in the gravel of higher heterogeneity grids, probably due to greater transport rates of O2 in the coarse-grained substratum. The H′ and probability of change indices indicated that the grids had levels of heterogeneity within the range of real streams. Grid depth to anoxia and substratum metabolism rates were similar to those found in streams, though less variable. In streams, H′ and probability of change values showed a slight difference among land use types, with some urban and agricultural sites displaying very low heterogeneity.

10aDissolved oxygen10anutrients10aO2 microelectrodes10astream10aSubstratum1 aWilson, K.C.1 aDodds, W., K. uhttps://link.springer.com/article/10.1007%2Fs10750-008-9647-y02518nas a2200169 4500008004100000245009700041210006900138300001300207490000800220520195400228100001902182700001702201700001802218700001802236700001702254856007702271 2009 eng d00aDisturbance frequency and functional identity mediate ecosystem processes in prairie streams0 aDisturbance frequency and functional identity mediate ecosystem  a917 -9330 v1183 a

A major consequence of climate change will be the alteration of precipitation patterns and concomitant changes in the flood frequencies in streams. Species losses or introductions will accompany these changes, which necessitates understanding the interactions between altered disturbance regimes and consumer functional identity to predict dynamics of streams. We used experimental mesocosms and field enclosures to test the interactive effects of flood frequency and two fishes from distinct consumer groups (benthic grazers and water-column minnows) on recovery of stream ecosystem properties (algal form and biomass, invertebrate densities, metabolism and nutrient uptake rates). Our results generally suggest that periphyton communities under nutrient limitation are likely to recover more quickly when grazing and water-column minnows are present and these effects can diminish or reverse with time since the disturbance. We hypothesized that increased periphyton production and biomass was the result of increased nutrient turnover, but decreased light limitation and indirect effects on other trophic levels are alternative explanations. Recovery of stream ecosystem properties after a natural flood differed from mesocosms (e.g. lower algal biomass and no long algal filaments present) and species manipulations did not explain recovery of ecosystem properties; rather, ecosystem processes varied along a downstream gradient of increasing temperature and nutrient concentrations. Different results between field enclosures and experimental mesocosms are attributable to a number of factors including differences in algal and invertebrate communities in the natural stream and relatively short enclosure lengths (mean area=35.8 m2) compared with recirculating water in the experimental mesocosms. These differences may provide insight into conditions necessary to elicit a strong interaction between consumers and ecosystem properties.

1 aBertrand, K.N.1 aGido, K., B.1 aDodds, W., K.1 aMurdock, J.N.1 aWhiles, M.R. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1600-0706.2008.16849.x01846nas a2200145 4500008004100000245010700041210006900148300001500217490000700232520135400239100001801593700001501611700001801626856005601644 2009 eng d00aThe influence of land use on stream biofilm nutrient limitation across eight North American ecoregions0 ainfluence of land use on stream biofilm nutrient limitation acro a1081 -10940 v663 a

Nutrient diffusing substrata were used to determine the influence of inorganic nitrogen (N) and phosphorus (P) availability on community respiration (CR), gross primary production (GPP), and chlorophyll a (chl a) on inorganic and organic substrata. We incubated substrata in nine streams each in a total of eight ecoregions (n = 72 streams) located in a range of native vegetation, agriculture, and urban land-use types. On organic substrata, CR was nutrient-limited in 94% of reference streams but showed significant nutrient limitation in only 60% and 65% of agricultural and urban streams, respectively. The relative magnitude of nutrient limitation for CR on organic substrata decreased with increasing percent modified land use in the basin (agriculture + urban). On inorganic and organic substrata, GPP and chl a were rarely nutrient-limited across all ecoregions and land-use types, although the magnitude of nutrient limitation increased with increasing light availability. The effect of human land use on nutrient limitation of biofilm CR, GPP, and chl a was influenced by ecoregion, yet heterotrophic biofilms were consistently most sensitive to nutrient enrichment across ecoregions. Both heterotrophic and autotrophic biofilm constituents should be considered to fully understand stream ecosystem responses to nutrient enrichment.

1 aJohnson, L.T.1 aTank, J.L.1 aDodds, W., K. uhttp://www.nrcresearchpress.com/doi/10.1139/F09-06500357nam a2200097 4500008004100000245004400041210004200085260004500127100001800172856006900190 2009 eng d00aLaws, Theories, and Patterns in Ecology0 aLaws Theories and Patterns in Ecology aBerkeleybUniversity of California Press1 aDodds, W., K. uhttp://129.130.186.12/content/laws-theories-and-patterns-ecology03146nas a2200469 4500008004100000245009200041210006900133300001300202490000700215520184400222100001502066700001502081700001702096700002102113700001802134700001802152700001802170700001702188700001602205700001902221700001602240700001902256700001802275700001902293700001602312700001802328700001502346700001702361700001902378700001702397700001902414700001702433700002302450700001802473700001702491700001902508700001702527700001702544700001902561700001702580856007902597 2009 eng d00aNitrate removal in stream ecosystems measured by 15N addition experiments: Total uptake0 aNitrate removal in stream ecosystems measured by 15N addition ex a653 -6650 v543 a

We measured uptake length of 15NO3− in 72 streams in eight regions across the United States and Puerto Rico to develop quantitative predictive models on controls of NO3− uptake length. As part of the Lotic Intersite Nitrogen eXperiment II project, we chose nine streams in each region corresponding to natural (reference), suburban-urban, and agricultural land uses. Study streams spanned a range of human land use to maximize variation in NO3− concentration, geomorphology, and metabolism. We tested a causal model predicting controls on NO3− uptake length using structural equation modeling. The model included concomitant measurements of ecosystem metabolism, hydraulic parameters, and nitrogen concentration. We compared this structural equation model to multiple regression models which included additional biotic, catchment, and riparian variables. The structural equation model explained 79% of the variation in log uptake length (SWtot). Uptake length increased with specific discharge (Q/w) and increasing NO3− concentrations, showing a loss in removal efficiency in streams with high NO3− concentration. Uptake lengths shortened with increasing gross primary production, suggesting autotrophic assimilation dominated NO3− removal. The fraction of catchment area as agriculture and suburban-urban land use weakly predicted NO3− uptake in bivariate regression, and did improve prediction in a set of multiple regression models. Adding land use to the structural equation model showed that land use indirectly affected NO3− uptake lengths via directly increasing both gross primary production and NO3− concentration. Gross primary production shortened SWtot, while increasing NO3− lengthened SWtot resulting in no net effect of land use on NO3− removal.

1 aHall, R.O.1 aTank, J.L.1 aSobota, D.J.1 aMulholland, P.J.1 aO'Brien, J.M.1 aDodds, W., K.1 aWebster, J.R.1 aValett, H.M.1 aPoole, G.C.1 aPeterson, B.J.1 aMeyer, J.L.1 aMcDowell, W.H.1 aJohnson, S.L.1 aHamilton, S.K.1 aGrimm, N.B.1 aGregory, S.V.1 aDahm, C.N.1 aCooper, L.W.1 aAshkenas, L.R.1 aThomas, S.M.1 aSheibley, R.W.1 aPotter, J.D.1 aNiederlehner, B.R.1 aJohnson, L.T.1 aHelton, A.M.1 aCrenshaw, C.M.1 aBurgin, A.J.1 aBernot, M.J.1 aBeaulieu, J.J.1 aArango, C.P. uhttps://aslopubs.onlinelibrary.wiley.com/doi/abs/10.4319/lo.2009.54.3.065303136nas a2200481 4500008004100000245009500041210006900136300001300205490000700218520179900225100002102024700001502045700001702060700001802077700002002095700001602115700001902131700001902150700001802169700001502187700001902202700001702221700001502238700001802253700001802271700001602289700001902305700001602324700001702340700001802357700001702375700001902392700001702411700001702428700001902445700001702464700001802481700002302499700001702522700001902539700001702558856007902575 2009 eng d00aNitrate removal in stream ecosystems measured by 15N addition experiments: Denitrification0 aNitrate removal in stream ecosystems measured by 15N addition ex a666 -6800 v543 a

We measured denitrification rates using a field 15NO3− tracer-addition approach in a large, cross-site study of nitrate uptake in reference, agricultural, and suburban-urban streams. We measured denitrification rates in 49 of 72 streams studied. Uptake length due to denitrification (SWdenn) ranged from 89 m to 184 km (median of 9050 m) and there were no significant differences among regions or land-use categories, likely because of the wide range of conditions within each region and land use. N2 production rates far exceeded N2O production rates in all streams. The fraction of total NO3− removal from water due to denitrification ranged from 0.5% to 100% among streams (median of 16%), and was related to NH4+ concentration and ecosystem respiration rate (ER). Multivariate approaches showed that the most important factors controlling SWden were specific discharge (discharge / width) and NO3− concentration (positive effects), and ER and transient storage zones (negative effects). The relationship between areal denitrification rate (Uden) and NO3− concentration indicated a partial saturation effect. A power function with an exponent of 0.5 described this relationship better than a Michaelis-Menten equation. Although Uden increased with increasing NO3− concentration, the efficiency of NO3− removal from water via denitrification declined, resulting in a smaller proportion of streamwater NO3− load removed over a given length of stream. Regional differences in stream denitrification rates were small relative to the proximate factors of NO3− concentration and ecosystem respiration rate, and land use was an important but indirect control on denitrification in streams, primarily via its effect on NO3− concentration.

1 aMulholland, P.J.1 aHall, R.O.1 aSobota, D.J.1 aDodds, W., K.1 aFindlay, S.E.G.1 aGrimm, N.B.1 aHamilton, S.K.1 aMcDowell, W.H.1 aO'Brien, J.M.1 aTank, J.L.1 aAshkenas, L.R.1 aCooper, L.W.1 aDahm, C.N.1 aGregory, S.V.1 aJohnson, S.L.1 aMeyer, J.L.1 aPeterson, B.J.1 aPoole, G.C.1 aValett, H.M.1 aWebster, J.R.1 aArango, C.P.1 aBeaulieu, J.J.1 aBernot, M.J.1 aBurgin, A.J.1 aCrenshaw, C.L.1 aHelton, A.M.1 aJohnson, L.T.1 aNiederlehner, B.R.1 aPotter, J.D.1 aSheibley, R.W.1 aThomas, S.M. uhttps://aslopubs.onlinelibrary.wiley.com/doi/abs/10.4319/lo.2009.54.3.066602315nas a2200169 4500008004100000245008700041210006900128300001500197490000700212520178700219100001602006700001802022700001702040700002002057700001702077856005102094 2009 eng d00aSpatial heterogeneity of denitrification genes in a highly homogenous urban stream0 aSpatial heterogeneity of denitrification genes in a highly homog a4273 -42790 v433 a

Human modification of natural streams by urbanization has led to more homogeneous channel surfaces; however, the influence of channel simplification on in situ microbial distribution and function is poorly characterized. For example, denitrification, a microbial process that reduces soluble nitrogen (N) levels, requires peripheral anoxic zones that might be lost in artificial channels such as those with a concrete lining. To examine how microbial function might be influenced by channel simplification, we quantified denitrification rates and conditions in microbial mats within an urban concrete channel. We quantified spatial and diurnal patterns of nitrate uptake, diurnal dissolved oxygen (DO) levels, and nutrient conditions, along with the spatial distribution of DO, solids, chlorophyll a, and genes associated with denitrification (nirS and nirK), ammonia-oxidizing bacteria (AOB), cyanobacteria, and algal chloroplasts. Despite the channel being superficially homogeneous, nir genes were distributed in a patchy manner. Two types of gene patches were observed: one associated with nirK, which had diurnally variable DO levels and high nocturnal nitrate uptake rates, and the other associated with nirS, which had elevated AOB genes, thicker layers of mud, and an apparent 24 h nitrate uptake. All active nir patches had elevated microbial photosynthetic genes. Results imply that even artificial channels, with reduced macroscale heterogeneity, can sustain significant rates of denitrification, although the responsible communities vary with space and time. This patchiness has significant implications to extending local data to landscape level predictions and field sampling strategies but also suggests alternate channel designs to increase N retention rates.

1 aKnapp, C.W.1 aDodds, W., K.1 aWilson, K.C.1 aO’Brien, J.M.1 aGraham, D.W. uhttps://pubs.acs.org/doi/abs/10.1021/es900140702510nas a2200205 4500008004100000245013400041210006900175300001300244490000700257520182000264653001402084653002202098653001902120653002102139653002502160100001902185700001602204700001802220856006602238 2009 eng d00aStream discharge and riparian land use influence in-stream concentrations and loads of phosphorus from Central Plains watersheds0 aStream discharge and riparian land use influence instream concen a552 -5650 v443 a

Total annual nutrient loads are a function of both watershed characteristics and the magnitude of nutrient mobilizing events. We investigated linkages among land cover, discharge and total phosphorus (TP) concentrations, and loads in 25 Kansas streams. Stream monitoring locations were selected from the Kansas Department of Health and Environment stream chemistry long-term monitoring network sites at or near U.S. Geological Survey stream gauges. We linked each sample with concurrent discharge data to improve our ability to estimate TP concentrations and loads across the full range of possible flow conditions. Median TP concentration was strongly linked (R 2 = 76%) to the presence of cropland in the riparian zones of the mostly perennial streams. At baseflow, discharge data did not improve prediction of TP, but at high flows discharge was strongly linked to concentration (a threshold response occurred). Our data suggest that on average 88% of the total load occurred during the 10% of the time with the greatest discharge. Modeled reductions in peak discharges, representing increased hydrologic retention, predicted greater decreases in total annual loads than reductions of ambient concentrations because high discharge and elevated phosphorus concentrations had multiplicative effects. No measure of land use provided significant predictive power for concentrations when discharge was elevated or for concentration rise rates under increasing discharge. These results suggest that reductions of baseflow concentrations of TP in streams without wastewater dischargers may be managed by reductions of cropland uses in the riparian corridor. Additional measures may be needed to manage TP annual loads, due to the large percentage of the TP load occurring during a few high-flow events each year.

10aDischarge10aPerennial streams10aRiparian zones10atotal phosphorus10aWatershed management1 aBanner, E.B.K.1 aStahl, A.J.1 aDodds, W., K. uhttps://link.springer.com/article/10.1007%2Fs00267-009-9332-603185nas a2200229 4500008004100000245013000041210006900171300001300240490000700253520244800260653001802708653001602726653001902742653002202761653002102783653001802804100002202822700001802844700001802862700001602880856005902896 2009 eng d00aThresholds in macroinvertebrate biodiversity and stoichiometry across water-quality gradients in Central Plains (USA) streams0 aThresholds in macroinvertebrate biodiversity and stoichiometry a a855 -8680 v283 a

N and P often limit primary and secondary production in ecosystems, but they also can cause eutrophication and negatively influence sensitive species above a certain level or threshold point. Aquatic biodiversity can have negative threshold relationships with water-quality variables at large scales, but the specific mechanism(s) driving these threshold relationships are not well established. We hypothesized that resource quality (i.e., C:P) might partly drive primary consumer (grazer and detritivore) richness thresholds by altering competitive interactions among species with differing resource demands, but might have less influence on predator richness. We estimated total N (TN), total P (TP), and turbidity thresholds for macroinvertebrate richness across trophic levels and feeding groups in Central Plains (USA) streams. We also determined if mean taxon body C:P of groups with diversity losses were negatively related to TP, a pattern that would suggest that eutrophic communities were dominated by a few species with high dietary P demands. Primary consumers were more sensitive to TN and TP (threshold mean  =  1.0 mg N/L and 0.06 mg P/L) than secondary consumers (threshold mean  =  0.09 mg P/L), a result supporting the resource quality hypothesis. Turbidity reduced richness regardless of feeding mode (threshold mean  =  4.7 NTU), a result suggesting that turbidity and nutrient thresholds were driven by different factors. The TP-richness threshold could be driven partially by changes in food quality because the mean body C:P of shredding and collector-gathering taxa declined as TP increased (threshold mean  =  0.07 and 0.75 mg P/L, respectively). Mean scraper C:P was not related to TP, a result indicating other factors might be responsible for the scraper richness threshold. Our results suggest that changes in resource quality could contribute to large-scale losses in biodiversity in nutrient-enriched lotic ecosystems. Within shredder and collector-gatherer macroinvertebrate feeding groups, P-rich food might allow faster growing taxa with high body P demands to out-compete slower growing taxa adapted to lower quality food resources. This pattern suggests that biotic integrity is directly linked to nutrients in streams and that toxicity, low dissolved O2, and increased turbidity might not be the only mechanisms leading to reductions in diversity as nutrient concentrations increase.

10abioassessment10abreakpoints10aeutrophication10anutrient criteria10aSpecies richness10awater quality1 aEvans-White, M.A.1 aDodds, W., K.1 aHuggins, D.G.1 aBaker, D.S. uhttps://www.journals.uchicago.edu/doi/10.1899/08-113.102063nas a2200133 4500008004100000245012300041210006900164300001300233490000700246520156300253100001801816700001801834856007701852 2008 eng d00aAmmonium uptake and mineralization in prairie streams: chamber incubation and short-term nutrient addition experiments0 aAmmonium uptake and mineralization in prairie streams chamber in a102 -1120 v533 a

1. We used two separate approaches to estimate ambient ammonium cycling in the north and south branches of Kings Creek, a prairie stream. Chamber experiments were conducted to determine ammonium uptake and mineralization rates associated with epilithic biofilms and filamentous algae collected from the streams. A series of short-term whole-stream ammonium addition experiments were also conducted to estimate the rate of uptake at ambient stream concentrations, based on the relationship between ammonium concentrations and uptake rates. 2. Chamber experiments were scaled up to whole-stream levels, resulting in ambient gross uptake estimates of 0.08 μg−2 s−1 for the north branch and 0.16 μg−2 s−1 for the south branch. The substrata-specific estimates of mineralization were higher than uptake in both streams. 3. Substrata-specific measurements indicated that ammonium uptake is higher in riffle habitats than in pools habitats. The results of the short-term ammonium addition experiments support these findings. 4. Short-term ammonium addition experiments show that uptake rates saturate with increasing ammonium concentrations. The observed saturation of uptake rates is consistent with a Michaelis–Menten relationship. 5. Scaled estimates of uptake from the chamber experiments were similar to estimates of ambient ammonium uptake based on the whole-stream experiments, and were comparable with previous estimates of ammonium uptake and mineralization made by using stable isotope tracer methods in Kings Creek.

1 aO'Brien, J.M.1 aDodds, W., K. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2427.2007.01870.x01828nas a2200265 4500008004100000245008100041210006900122300001300191490000700204520104600211653001701257653002001274653002301294653002401317653001601341100001801357700001701375700001901392700001701411700001501428700001601443700002001459700001901479856006401498 2008 eng d00aComparing ecosystem goods and services provided by restored and native lands0 aComparing ecosystem goods and services provided by restored and  a837 -8450 v583 a

We determined the relative benefits for eight categories of ecosystem goods and services associated with native and restored lands across the conterminous United States. Less than 10% of most native US ecosystems remain, and the proportion that is restored varies widely by biome. Restored lands offer 31% to 93% of native land benefits within a decade after restoration, with restored wetlands providing the most economic value and deserts providing the least. Restored ecosystems that recover rapidly and produce valuable commodities return a higher proportion of total value. The relative values of the benefits provided by restoration vary both by biome and by the ecosystem goods and services of interest. Our analysis confirms that conservation should be the first priority, but that restoration programs across broad geographic regions can have substantial value. “No net loss” policies should recognize that restored lands are not necessarily equivalent to native areas with regard to estimated ecosystem benefits.

10aconservation10aecosystem goods10aecosystem services10aecosystem valuation10arestoration1 aDodds, W., K.1 aWilson, K.C.1 aRehmeier, R.L.1 aKnight, G.L.1 aWiggam, S.1 aFalke, J.A.1 aDalgleish, H.J.1 aBertrand, K.N. uhttps://academic.oup.com/bioscience/article/58/9/837/25093902269nas a2200205 4500008004100000245005300041210005300094300001300147490000700160520164700167653003501814653002201849653003001871653001901901653001801920653002501938100001801963700001601981856006601997 2008 eng d00aHeadwater influences on downstream water quality0 aHeadwater influences on downstream water quality a367 -3770 v413 a

We investigated the influence of riparian and whole watershed land use as a function of stream size on surface water chemistry and assessed regional variation in these relationships. Sixty-eight watersheds in four level III U.S. EPA ecoregions in eastern Kansas were selected as study sites. Riparian land cover and watershed land use were quantified for the entire watershed, and by Strahler order. Multiple regression analyses using riparian land cover classifications as independent variables explained among-site variation in water chemistry parameters, particularly total nitrogen (41%), nitrate (61%), and total phosphorus (63%) concentrations. Whole watershed land use explained slightly less variance, but riparian and whole watershed land use were so tightly correlated that it was difficult to separate their effects. Water chemistry parameters sampled in downstream reaches were most closely correlated with riparian land cover adjacent to the smallest (first-order) streams of watersheds or land use in the entire watershed, with riparian zones immediately upstream of sampling sites offering less explanatory power as stream size increased. Interestingly, headwater effects were evident even at times when these small streams were unlikely to be flowing. Relationships were similar among ecoregions, indicating that land use characteristics were most responsible for water quality variation among watersheds. These findings suggest that nonpoint pollution control strategies should consider the influence of small upland streams and protection of downstream riparian zones alone is not sufficient to protect water quality.

10ageographic information systems10aHeadwater streams10aNonpoint source pollution10aRiparian zones10awater quality10aWatershed management1 aDodds, W., K.1 aOakes, R.M. uhttps://link.springer.com/article/10.1007%2Fs00267-007-9033-y00431nam a2200097 4500008004100000245007000041210006700111260004000178100001800218856009700236 2008 eng d00aHumanity's Footprint: Momentum, Impact and our Global Environment0 aHumanitys Footprint Momentum Impact and our Global Environment aNew YorkbColumbia University Press1 aDodds, W., K. uhttp://129.130.186.12/content/humanitys-footprint-momentum-impact-and-our-global-environment01632nas a2200157 4500008004100000245010000041210006900141300001300210490000600223520110300229100002101332700001801353700001601371700001501387856007201402 2008 eng d00aLakes and streams as sentinels of environmental change in terrestrial and atmospheric processes0 aLakes and streams as sentinels of environmental change in terres a247 -2540 v63 a

Recent advances in our understanding of the importance of continental- to global-scale connectivity among terrestrial and aquatic ecosystems make consideration of aquatic–terrestrial linkages an urgent ecological and environmental issue. Here, we describe the role of inland waters as sentinels and integrators of the impact of humans on terrestrial and aquatic ecosystems. The metabolic responses of lakes and streams (ie the rates at which these systems process carbon) are proposed as a common metric to integrate the impacts of environmental change across a broad range of landscapes. Lakes and streams transport and alter nutrients, contaminants, and energy, and store signals of environmental change from local to continental scales over periods ranging from weeks to millennia. A carefully conceived and well-integrated network that includes monitoring and experimental approaches to terrestrial–aquatic connectivity is critical to an understanding of basic ecosystem-level processes and to forecasting and mitigating future environmental impacts at the continental scale.

1 aWilliamson, C.E.1 aDodds, W., K.1 aKratz, T.K.1 aPalmer, M. uhttps://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/07014000549nas a2200121 4500008004100000245013600041210006900177300001300246490000700259100001800266700001800284856012500302 2008 eng d00aPredicting NH4+ uptake andmineralization in prairie streams by using chamber incubation and short-termnutrient addition experiments0 aPredicting NH4 uptake andmineralization in prairie streams by us a102 -1120 v521 aO'Brien, J.M.1 aDodds, W., K. uhttp://129.130.186.12/content/predicting-nh4-uptake-andmineralization-prairie-streams-using-chamber-incubation-and-short02900nas a2200481 4500008004100000245009100041210006900132300001300201490000800214520160100222100002101823700001701844700001601861700001501877700001901892700001901911700001501930700001901945700001701964700001501981700001801996700002002014700001802034700001602052700001802068700001902086700001602105700001702121700001802138700001702156700001902173700001702192700001702209700001702226700001602243700002302259700001802282700001702300700001902317700001702336700001702353856004802370 2008 eng d00aStream denitrification across biomes and its response to anthropogenic nitrate loading0 aStream denitrification across biomes and its response to anthrop a202 -2070 v4523 a

Anthropogenic addition of bioavailable nitrogen to the biosphere is increasing1, 2 and terrestrial ecosystems are becoming increasingly nitrogen-saturated3, causing more bioavailable nitrogen to enter groundwater and surface waters4, 5, 6. Large-scale nitrogen budgets show that an average of about 20–25 per cent of the nitrogen added to the biosphere is exported from rivers to the ocean or inland basins7, 8, indicating that substantial sinks for nitrogen must exist in the landscape9. Streams and rivers may themselves be important sinks for bioavailable nitrogen owing to their hydrological connections with terrestrial systems, high rates of biological activity, and streambed sediment environments that favour microbial denitrification6, 10, 11. Here we present data from nitrogen stable isotope tracer experiments across 72 streams and 8 regions representing several biomes. We show that total biotic uptake and denitrification of nitrate increase with stream nitrate concentration, but that the efficiency of biotic uptake and denitrification declines as concentration increases, reducing the proportion of in-stream nitrate that is removed from transport. Our data suggest that the total uptake of nitrate is related to ecosystem photosynthesis and that denitrification is related to ecosystem respiration. In addition, we use a stream network model to demonstrate that excess nitrate in streams elicits a disproportionate increase in the fraction of nitrate that is exported to receiving waters and reduces the relative role of small versus large streams as nitrate sinks.

1 aMulholland, P.J.1 aHelton, A.M.1 aPoole, G.C.1 aHall, R.O.1 aHamilton, S.K.1 aPeterson, B.J.1 aTank, J.L.1 aAshkenas, L.R.1 aCooper, L.W.1 aDahm, C.N.1 aDodds, W., K.1 aFindlay, S.E.G.1 aGregory, S.V.1 aGrimm, N.B.1 aJohnson, S.L.1 aMcDowell, W.H.1 aMeyer, J.L.1 aValett, H.M.1 aWebster, J.R.1 aArango, C.P.1 aBeaulieu, J.J.1 aBernot, M.J.1 aBurgin, A.J.1 aCrenshaw, C.1 aJohnson, L.1 aNiederlehner, B.R.1 aO'Brien, J.M.1 aPotter, J.D.1 aSheibley, R.W.1 aSobota, D.J.1 aThomas, S.M. uhttps://www.nature.com/articles/nature0668602299nas a2200181 4500008004100000245009500041210006900136300001300205490000700218520168400225653001601909653001401925653001801939653001801957100001801975700001501993856010902008 2007 eng d00aExpanding the concept of trophic state in aquatic ecosystems: It's not just the autotrophs0 aExpanding the concept of trophic state in aquatic ecosystems Its a427 -4390 v693 a“Trophic state” is often used to classify aquatic ecosystems according to biotic productivity. Primary productivity (or a surrogate for it) has always been used as the metric of trophic state. We make the case here that both primary production and key heterotrophic processes are needed to evaluate trophic state. Defined as the relative flux rate of carbon (C) into the food web, trophic state is a fundamental property that is intimately related to both ecosystem structure and how humans influence water quality. Rates of heterotrophic activity can exceed primary production in many aquatic ecosystems including oceans, lakes, and streams. A comprehensive definition of trophic state with respect to aquatic food webs requires accounting for both the oxidation of organic C (respiration) and photosynthetic fixation of inorganic C (primary production). This inclusive definition is required because food webs can be fueled in part by allochthonous C. We propose autotrophic and heterotrophic states be defined by rates of photosynthetic and respiratory C fluxes respectively, and both be used to characterize ecosystems. Cumulative frequency distributions of both can be developed for minimally impacted aquatic systems as a baseline against which to compare human-influenced sites as well as for describing the range of conditions that aquatic organisms have experienced in their recent evolutionary history. Subsidies of organic C and inorganic nutrients to aquatic ecosystems influence heterotrophic state, so characterizing the base of the food web necessitates a stoichiometric view of supply rates, use efficiencies, and recycling of inorganic and organic materials.10aautotrophic10aecosystem10aheterotrophic10aTrophic state1 aDodds, W., K.1 aCole, J.J. uhttp://129.130.186.12/content/expanding-concept-trophic-state-aquatic-ecosystems-its-not-just-autotrophs02262nas a2200205 4500008004100000245006600041210006600107300001300173490000700186520162600193653002401819653002201843653001601865653001501881653001401896653001701910100001801927700001801945856009301963 2007 eng d00aLinking benthic algal biomass to stream substratum topography0 aLinking benthic algal biomass to stream substratum topography a449 -4600 v433 aThe physical properties of substrata significantly influence benthic algal development. We explored the relationships among substratum surface texture and orientation with epilithic microphytobenthic biomass accumulation at the whole-substratum and micrometer scales. Unglazed clay tiles set at three orientations (horizontal, vertical, and 45°), and six substrata of varying surface roughness were deployed in a prairie stream for 3 weeks. Substrata were analyzed for loosely attached, adnate, and total benthic algal biomass as chl a, and confocal laser scanning microscopy was used to measure substrata microtopography (i.e., roughness, microscale slope angles, and three-dimensional surface area). At the whole-substratum level, vertical substrata collected significantly (P < 0.05) less algal biomass, averaging 34% and 36% less than horizontal and 45° substrata, respectively. Benthic algal biomass was also significantly less on smoother surfaces; glass averaged 29% less biomass than stream rocks. At the microscale level, benthic algal biomass was the greatest at intermediate values, peaking at a mean roughness of approximately 17 μm, a mean microscale slope of 50°, and a projected/areal surface area ratio of 2:1. The proportion of adnate algae increased with surface roughness (26% and 67% for glass and brick, respectively), suggesting that substratum type changes the efficiency of algal removal by brushing. Individual substrata and microsubstrata characteristics can have a strong effect on benthic algae development and potentially affect reach scale algal variability as mediated by geomorphology.10aconfocal microscopy10amicrophytobenthos10aorientation10aperiphyton10aroughness10asurface area1 aMurdock, J.N.1 aDodds, W., K. uhttp://129.130.186.12/content/linking-benthic-algal-biomass-stream-substratum-topography02550nas a2200241 4500008004100000245012500041210006900166300001100235490000700246520175400253653002002007653001202027653001802039653001502057653001102072653001102083100001802094700001802112700001702130700001802147700001902165856012402184 2007 eng d00aThe saturation of N cycling in Central Plains streams: 15N experiments across a broad gradient of nitrate concentrations0 asaturation of N cycling in Central Plains streams 15N experiment a31 -490 v843 aWe conducted 15NO 3 − stable isotope tracer releases in nine streams with varied intensities and types of human impacts in the upstream watershed to measure nitrate (NO 3 − ) cycling dynamics. Mean ambient NO 3 − concentrations of the streams ranged from 0.9 to 21,000 μg l−1 NO 3 − –N. Major N-transforming processes, including uptake, nitrification, and denitrification, all increased approximately two to three orders of magnitude along the same gradient. Despite increases in transformation rates, the efficiency with which stream biota utilized available NO 3 − -decreased along the gradient of increasing NO 3 − . Observed functional relationships of biological N transformations (uptake and nitrification) with NO 3 − concentration did not support a 1st order model and did not show signs of Michaelis–Menten type saturation. The empirical relationship was best described by a Efficiency Loss model, in which log-transformed rates (uptake and nitrification) increase with log-transformed nitrate concentration with a slope less than one. Denitrification increased linearly across the gradient of NO 3 − concentrations, but only accounted for ∼1% of total NO 3 − uptake. On average, 20% of stream water NO 3 − was lost to denitrification per km, but the percentage removed in most streams was <5% km−1. Although the rate of cycling was greater in streams with larger NO 3 − concentrations, the relative proportion of NO 3 − retained per unit length of stream decreased as NO 3 − concentration increased. Due to the rapid rate of NO 3 − turnover, these streams have a great potential for short-term retention of N from the landscape, but the ability to remove N through denitrification is highly variable.10adenitrification10aNitrate10anitrification10aSaturation10astream10aUptake1 aO'Brien, J.M.1 aDodds, W., K.1 aWilson, K.C.1 aMurdock, J.N.1 aEichmiller, J. uhttp://129.130.186.12/content/saturation-n-cycling-central-plains-streams-15n-experiments-across-broad-gradient-nitrate01310nas a2200121 4500008004100000245006800041210006600109300001300175490000700188520088200195100001801077856009301095 2007 eng d00aTrophic state, eutrophication, and nutrient criteria in streams0 aTrophic state eutrophication and nutrient criteria in streams a669 -6760 v223 aTrophic state is the property of energy availability to the food web and defines the foundation of community integrity and ecosystem function. Describing trophic state in streams requires a stoichiometric (nutrient ratio) approach because carbon input rates are linked to nitrogen and phosphorus supply rates. Light determines the source of carbon. Cross system analyses, small experiments and ecosystem level manipulations have recently advanced knowledge about these linkages, but not to the point of building complex predictive models that predict all effects of nutrient pollution. Species diversity could indicate the natural distribution of stream trophic status over evolutionary time scales. Delineation of factors that control trophic state and relationships with biological community properties allows determination of goals for management of stream biotic integrity.1 aDodds, W., K. uhttp://129.130.186.12/content/trophic-state-eutrophication-and-nutrient-criteria-streams02560nas a2200193 4500008004100000245009700041210006900138300001300207490000700220520190300227653001302130653001502143653002202158653001302180653001802193100001802211700001602229856012102245 2006 eng d00aControls on nutrients across a prairie stream watershed: Land use and riparian cover effects0 aControls on nutrients across a prairie stream watershed Land use a636 -6460 v373 aNutrient inputs generally are increased by human-induced land use changes and can lead to eutrophication and impairment of surface waters. Understanding the scale at which land use influences nutrient loading is necessary for the development of management practices and policies that improve water quality. The authors assessed the relationships between land use and stream nutrients in a prairie watershed dominated by intermittent stream flow in the first-order higher elevation reaches. Total nitrogen, nitrate, and phosphorus concentrations were greater in tributaries occupying the lower portions of the watershed, closely mirroring the increased density of row crop agriculture from headwaters to lower-elevation alluvial areas. Land cover classified at three spatial scales in each sub-basin above sampling sites (riparian in the entire catchment, catchment land cover, and riparian across the 2 km upstream) was highly correlated with variation in both total nitrogen (r2 = 53%, 52%, and 49%, respectively) and nitrate (r2 = 69%, 65%, and 56%, respectively) concentrations among sites. However, phosphorus concentrations were not significantly associated with riparian or catchment land cover classes at any spatial scale. Separating land use from riparian cover in the entire watershed was difficult, but riparian cover was most closely correlated with in-stream nutrient concentrations. By controlling for land cover, a significant correlation of riparian cover for the 2 km above the sampling site with in-stream nutrient concentrations could be established. Surprisingly, land use in the entire watershed, including small intermittent streams, had a large influence on average downstream water quality although the headwater streams were not flowing for a substantial portion of the year. This suggests that nutrient criteria may not be met only by managing permanently flowing streams.10anitrogen10aPhosphorus10aPrairie watershed10aRiparian10awater quality1 aDodds, W., K.1 aOakes, R.M. uhttp://129.130.186.12/content/controls-nutrients-across-prairie-stream-watershed-land-use-and-riparian-cover-effects02543nas a2200205 4500008004100000245012700041210006900168300001300237490000700250520182200257653001402079653001902093653001302112653002202125653001502147100001802162700001502180700001702195856012502212 2006 eng d00aDetermining ecoregional reference conditions for nutrients, secchi depth, and chlorophyll a in Kansas lakes and reservoirs0 aDetermining ecoregional reference conditions for nutrients secch a151 -1590 v223 aBaseline environmental conditions are a critical consideration in the development of scientifically defensible aquatic nutrient criteria. We applied three methods to ecoregionally stratified data to determine reference conditions in Kansas lakes and reservoirs with respect to total phosphorus, total nitrogen, Secchi depth, and planktonic chlorophyll a (chl a). First, minimally developed lake/watershed units were identified based on existing geographical databases and visual basin surveys. Lakes and reservoirs in these watersheds were considered minimally-to-least impacted “reference” waters. Second, median nutrient, Secchi depth, and chl a values were determined for the best one-third of lakes and reservoirs and applied as indicators of reference condition (trisection). Third, a regression-based extrapolation method was applied to estimate water quality conditions in the absence of anthropogenic influences. The first method suggested no ecoregional effect on the trophic status of minimally impacted reference water bodies, whereas the other two methods indicated some significant ecoregional differences. Lack of ecoregional effect in reference bodies could indicate that differences were driven by anthropogenic influences rather than natural regional characteristics. Reference conditions, as determined by these three methods, broadly agreed for all parameters and were generally at or less than literature values for the mesotrophic-eutrophic threshold for lakes and reservoirs worldwide. Reference values for total phosphorus were primarily less than levels commonly associated with cyanobacterial blooms. Overall, the data suggest that multiple methods can be used to determine reference condition, and that in Kansas lakes and reservoirs reference condition corresponds to mesotrophic state.10aecoregion10aeutrophication10anitrogen10anutrient criteria10aPhosphorus1 aDodds, W., K.1 aCarney, E.1 aAngelo, R.T. uhttp://129.130.186.12/content/determining-ecoregional-reference-conditions-nutrients-secchi-depth-and-chlorophyll-kansas02161nas a2200121 4500008004100000245005900041210005900100300001300159490000700172520175600179100001801935856008601953 2006 eng d00aEutrophication and trophic state in rivers and streams0 aEutrophication and trophic state in rivers and streams a671 -6800 v513 aMany natural streams are net heterotrophic, so I propose that trophic state be divided into autotrophic and heterotrophic state. This division allows consideration of the influence of external carbon sources as well as nutrients such as nitrogen and phosphorus. Empirical results suggest that phosphorus and nitrogen are the most important nutrients regulating autotrophic state in flowing waters and that benthic algal biomass is positively correlated to gross primary production in streams. Reference (minimally influenced by human activities) nutrient concentrations and correlations of nutrients with algal biomass are used to characterize reference distributions of stream autotrophic state. Only when reference nutrient concentrations are in the upper one third of those expected in the United States, is maximum benthic chlorophyll projected to exceed 100 mg m!2 (a concentration commonly used to indicate nuisance levels) "30% of the time. Average reference nutrient concentrations lead to sestonic chlorophyll concentrations above those considered typical of eutrophic lakes ("8 mg m!3 ) less than half the time. Preliminary analysis suggests that autotrophic state is variable in small pristine streams because it is influenced by canopy cover (light), but heterotrophic state is less variable because it can be based on allochthonous or autochthonous production. Nitrogen and phosphorus enrichment can influence both heterotrophic and autotrophic state, and these effects could cascade to animal communities. Stoichiometry should be considered because carbon, nitrogen, and phosphorus are all involved in trophic state. The proposed definition of trophic state offers a starting conceptual framework for such considerations.1 aDodds, W., K. uhttp://129.130.186.12/content/eutrophication-and-trophic-state-rivers-and-streams00501nas a2200109 4500008004100000245012100041210006900162300001300231490000600244100001800250856012300268 2006 eng d00aNutrients and the Dead Zone: Ecological stoichiometry and depressed dissolved oxygen in the northern Gulf of Mexico0 aNutrients and the Dead Zone Ecological stoichiometry and depress a211 -2170 v41 aDodds, W., K. uhttp://129.130.186.12/content/nutrients-and-dead-zone-ecological-stoichiometry-and-depressed-dissolved-oxygen-northern01513nas a2200133 4500008004100000245005400041210005200095300001300147490000800160520109700168100001801265700001701283856007901300 2006 eng d00aRedefining the community:a species-based approach0 aRedefining the communitya speciesbased approach a464 -4720 v1123 aWe propose that effective community size can be defined on the basis of the web of indirect interactions experienced on average by each individual species. Indirect interaction chains are composed of links provided by direct interactions. We analyzed previously published data on 20 assemblages of species. Chain strengths were estimated by the weakest link and by the product of link strength. The average strength of the interaction chain decreased with increasing numbers of links with both models. Positive indirect interactions in chains with an even number of links offset negative direct interactions. We set the community size by the chain length where 95% of the indirect interactions are weaker than 10% of the mean of the absolute value of direct interaction strength. Using the multiplicative model, seven assemblages had a community size (web of interaction length) of three links, one of four links, and the remainder of communities were too small to set community size. The analysis suggests that effective communities of size are rarely investigated in ecological experiments.1 aDodds, W., K.1 aNelson, J.A. uhttp://129.130.186.12/content/redefining-communitya-species-based-approach01906nas a2200217 4500008004100000245008400041210006900125300001300194490000700207520119900214653002101413653002201434653001301456653001701469653002601486100001701512700001801529700001601547700001401563856011101577 2006 eng d00aTemperature and kairomone induced life history plasticity in coexisting Daphnia0 aTemperature and kairomone induced life history plasticity in coe a361 -3720 v403 aWe investigated the life history alterations of coexisting Daphnia species responding to environmental temperature and predator cues. In a laboratory experiment, we measured Daphnia life history plasticity under different predation risk and temperature treatments that simulate changing environmental conditions. Daphnia pulicaria abundance and size at first reproduction (SFR) declined, while ephippia (resting egg) formation increased at high temperatures. Daphnia mendotae abundance and clutch size increased with predation risk at high temperatures, but produced few ephippia. Thus, each species exhibited phenotypic plasticity, but responded in sharply different ways to the same environmental cues. In Glen Elder reservoir, Kansas USA, D. pulicaria dominance shifted to D. mendotae dominance as temperature and predation risk increased from March to June in both 1999 and 2000. Field estimates of life history shifts mirrored the laboratory experiment results, suggesting that similar phenotypic responses to seasonal cues contribute to seasonal Daphnia population trends. These results illustrate species-specific differences in life history plasticity among coexisting zooplankton taxa.10aDaphnia mendotae10aDaphnia pulicaria10aEphippia10aLife history10aPhenotypic plasticity1 aBernot, R.J.1 aDodds, W., K.1 aQuist, M.C.1 aGuy, C.S. uhttp://129.130.186.12/content/temperature-and-kairomone-induced-life-history-plasticity-coexisting-daphnia00364nas a2200121 4500008004100000245004000041210004000081300001300121490000600134100001700140700001800157856006700175 2005 eng d00aChronic nitrogen loading in streams0 aChronic nitrogen loading in streams a442 -4530 v81 aBernot, M.J.1 aDodds, W., K. uhttp://129.130.186.12/content/chronic-nitrogen-loading-streams01530nas a2200169 4500008004100000245007600041210006900117300001300186490000600199520096800205100001501173700001801188700002101206700001701227700001801244856009801262 2005 eng d00aEstimation of stream nutrient uptake from nutrient addition experiments0 aEstimation of stream nutrient uptake from nutrient addition expe a174 -1820 v33 aNutrient uptake in streams is often quantified by determining nutrient uptake length. However, current methods for measuring nutrient uptake length are often impractical, expensive, or demonstrably incorrect. We have developed a new method to estimate ambient nutrient uptake lengths using field experiments involving several levels of nutrient addition. Data analysis involves plotting nutrient addition uptake lengths versus added concentration and extrapolating to the negative ambient concentration. This method is relatively easy, inexpensive, and based on sound theoretical development. It is more accurate than the commonly used method involving a single nutrient addition. The utility of the method is supported by field studies directly comparing our new method with isotopic tracer methods for determining uptake lengths of phosphorus, ammonium, and nitrate. Our method also provides parameters for comparing potential nutrient limitation among streams.1 aPayn, R.A.1 aWebster, J.R.1 aMulholland, P.J.1 aValett, H.M.1 aDodds, W., K. uhttp://129.130.186.12/content/estimation-stream-nutrient-uptake-nutrient-addition-experiments02391nas a2200133 4500008004100000245008300041210006900124300001100193490000700204520190300211100001602114700001802130856010902148 2005 eng d00aHarshness: characterization of intermittent stream habitat over space and time0 aHarshness characterization of intermittent stream habitat over s a13 -230 v563 aFrequently disturbed environments, such as intermittent streams, are ecologically useful for studying how disturbance characteristics (e.g. frequency, magnitude) affect community structure and succession. We developed a harshness index that quantifies ecologically pertinent spatial and temporal characteristics of prairie intermittent streams that may limit or reduce diversity and abundance to predict benthic macroinvertebrate assemblage characteristics. The index incorporates 11 variables that describe the hydrological regime (e.g. average flow, flow variability, drying and flooding) and distance to perennial surface water. We started with 27 variables, but removed 16 that did not increase the predictive value of the index. The relationships among index values and annual mean macroinvertebrate assemblage characteristics (taxonomic richness, diversity, evenness and abundance) were tested over two years using seven sites that represent a range of flow permanence (recent and historical), flood magnitude (recent and historical) and surface-water connectivity. Mean annual taxonomic richness was significantly related to the harshness index. Evenness and abundance were not related to harshness. Further analyses indicated that distance to the nearest permanent habitat was less important than annual or historical hydrological parameters, even though prior research had documented higher rates of colonisation at sites that were closer to nearest permanent habitat. Both annual factors that can alter abundance and colonisation immediately (e.g. floods, drought in each year) and historical factors (e.g. probability of drying, average length of dry period over decades) may influence assemblage characteristics. Historical factors may influence evolutionary adaptations of invertebrates and may predominate when relative disturbance rates are lower such as in years with less flooding.1 aFritz, K.M.1 aDodds, W., K. uhttp://129.130.186.12/content/harshness-characterization-intermittent-stream-habitat-over-space-and-time02511nas a2200313 4500008004100000245007600041210006900117300001300186490000800199520160300207653001101810653002601821653001301847653001801860653001201878100001801890700001401908700001301922700001801935700001901953700001601972700001701988700001902005700001902024700001702043700001802060700001602078856010302094 2004 eng d00aCarbon and nitrogen stoichiometry and nitrogen cycling rates in streams0 aCarbon and nitrogen stoichiometry and nitrogen cycling rates in  a458 -4670 v1403 aStoichiometric analyses can be used to investigate the linkages between N and C cycles and how these linkages influence biogeochemistry at many scales, from components of individual ecosystems up to the biosphere. N-specific NH4 + uptake rates were measured in eight streams using short-term 15N tracer additions, and C to N ratios (C:N) were determined from living and non-living organic matter collected from ten streams. These data were also compared to previously published data compiled from studies of lakes, ponds, wetlands, forests, and tundra. There was a significant negative relationship between C:N and N-specific uptake rate; C:N could account for 41% of the variance in N-specific uptake rate across all streams, and the relationship held in five of eight streams. Most of the variation in N-specific uptake rate was contributed by detrital and primary producer compartments with large values of C:N and small values for N-specific uptake rate. In streams, particulate materials are not as likely to move downstream as dissolved N, so if N is cycling in a particulate compartment, N retention is likely to be greater. Together, these data suggest that N retention may depend in part on C:N of living and non-living organic matter in streams. Factors that alter C:N of stream ecosystem compartments, such as removal of riparian vegetation or N fertilization, may influence the amount of retention attributed to these ecosystem compartments by causing shifts in stoichiometry. Our analysis suggests that C:N of ecosystem compartments can be used to link N-cycling models across streams.10acarbon10aCarbon:Nitrogen ratio10anitrogen10astoichiometry10astreams1 aDodds, W., K.1 aMarti, E.1 aTank, J.1 aPontius, J.L.1 aHamilton, S.K.1 aGrimm, N.B.1 aBowden, W.B.1 aMcDowell, W.H.1 aPeterson, B.J.1 aValett, H.M.1 aWebster, J.R.1 aGregory, S. uhttp://129.130.186.12/content/carbon-and-nitrogen-stoichiometry-and-nitrogen-cycling-rates-streams01523nas a2200169 4500008004100000245006600041210006500107300001300172490000700185520099300192100001801185700001701203700001701220700001601237700001901253856008101272 2004 eng d00aLife on the edge: the ecology of Great Plains prairie streams0 aLife on the edge the ecology of Great Plains prairie streams a207 -2810 v543 aGreat Plains streams are highly endangered and can serve as model systems for studying disturbance ecology and related issues of resistance and resilience in temperate freshwaters. These streams exist in a precarious balance between flood and drying. In general, microbial activity recovers in days to weeks after drying or flooding, and invertebrate and fish species are quick to follow. In lower forested reaches, floods may be more intense but drying less common. Upstream reaches of prairie streams are characterized by frequent drying, little canopy cover, and limited leaf input. Life history and adaptations alter the ways in which stream organisms respond to these linear patterns. Human modification has altered these patterns, leading to large-scale loss of native grassland streams. The future for Great Plains streams is bleak, given the land-use changes and water-use patterns in the region and the large areas required to preserve intact, ecologically functional watersheds.1 aDodds, W., K.1 aGido, K., B.1 aWhiles, M.R.1 aFritz, K.M.1 aMatthews, W.J. uhttp://129.130.186.12/content/life-edge-ecology-great-plains-prairie-streams02308nas a2200253 4500008004100000245010500041210006900146300001300215490000700228520150300235653001501738653001301753653001401766653001101780653002301791653001401814653001801828100001801846700001701864700001701881700001601898700001901914856012101933 2004 eng d00aQuality and quantity of suspended particles in rivers: Continent-scale patterns in the United States0 aQuality and quantity of suspended particles in rivers Continents a355 -3670 v333 aSuspended solids or sediments can be pollutants in rivers, but they are also an important component of lotic food webs. Suspended sediment data for rivers were obtained from a United States–wide water quality database for 622 stations. Data for particulate nitrogen, suspended carbon, discharge, watershed area, land use, and population were also used. Stations were classified by United States Environmental Protection Agency ecoregions to assess relationships between terrestrial habitats and the quality and quantity of total suspended solids (TSS). Results indicate that nephelometric determinations of mean turbidity can be used to estimate mean suspended sediment values to within an order of magnitude (r2 = 0.89). Water quality is often considered impaired above 80 mg TSS L−1, and 35% of the stations examined during this study had mean values exceeding this level. Forested systems had substantially lower TSS and somewhat higher carbon-to-nitrogen ratios of suspended materials. The correlation between TSS and discharge was moderately well described by an exponential relationship, with the power of the exponent indicating potential acute sediment events in rivers. Mean sediment values and power of the exponent varied significantly with ecoregion, but TSS values were also influenced by land use practices and geomorphological characteristics. Results confirm that, based on current water quality standards, excessive suspended solids impair numerous rivers in the United States.10aEcoregions10aLand use10apollution10aSeston10aSuspended sediment10aTurbidity10awater quality1 aDodds, W., K.1 aGido, K., B.1 aWhiles, M.R.1 aFritz, K.M.1 aMatthews, W.J. uhttp://129.130.186.12/content/quality-and-quantity-suspended-particles-rivers-continent-scale-patterns-united-states02468nas a2200205 4500008004100000245012000041210006900161300001200230490000800242520180000250653001602050653001102066653001102077653002502088653002302113653002002136100001602156700001802172856007202190 2004 eng d00aResistance and resilience of macroinvertebrate assemblages to drying and flood in a tallgrass prairie stream system0 aResistance and resilience of macroinvertebrate assemblages to dr a99 -1120 v5973 aIntermittent streams are common worldwide, and the ability of invertebrates to recover from floods and drought is a key feature of communities from these highly disturbed ecosystems. The macroinvertebrate assemblages of Kings Creek in northeastern Kansas were sampled regularly from four intermittent and two perennial sites over 2 years (1995–1996) to investigate the response and recovery to seasonal drying and floods. A ≈9mo drying period reduced taxa richness and density to 14% and 3% of pre-drying assemblages, respectively, in 1995–1996, whereas a 2mo drying period reduced richness by half and density to 4% of pre-drying assemblages in 1996. Floods at intermittent sites reduced densities and richness by 95% and ≈50%, respectively. A >50 y-flood reduced macroinvertebrate richness by 97% and density by >99% at a downstream perennial site. Resistance and resilience of total macroinvertebrate density was typically greater to floods than to drying, whereas resilience of taxa richness did not differ between disturbance types. The time required for recovery to pre-flood conditions (richness and density) was half as long (27 vs. 76 day) for intermittent sites compared to perennial sites. Colonization of intermittent sites was a function of distance from upstream refugia. Floods were a more important disturbance on assemblages in a downstream reach as compared to upstream reaches. In contrast, upstream reaches were more likely to dry. Recovery following flood and drought was dominated by colonization as opposed to tolerance, thus resilience is more important than resistance in regulating macroinvertebrate communities in these streams, and relative position in the landscape affects disturbance type, intensity, and ability of communities to recover from disturbance.10adisturbance10adrying10afloods10aintermittent streams10amacroinvertebrates10aprairie streams1 aFritz, K.M.1 aDodds, W., K. uhttp://link.springer.com/article/10.1023/B:HYDR.0000043188.53497.9b02413nas a2200133 4500008004100000245010400041210006900145300001300214490000600227520188900233100001802122700001402140856012502154 2004 eng d00aA technique for establishing reference nutrient concentrations across watersheds impacted by humans0 atechnique for establishing reference nutrient concentrations acr a333 -3410 v23 aEstablishing reference nutrient conditions for rivers and streams is necessary to assess human impact on aquatic ecosystems and protect water quality and biotic integrity. Several methods have been proposed: (1) percentiles from statistical distributions of all rivers and streams in a region or dataset, (2) reference stream approaches, and (3) modeling river networks from existing reference streams. We propose an additional statistical method to estimate the influence of anthropogenic land uses on lotic nutrient concentrations. First, we quantify regional variation by using analysis of covariance, where total nitrogen or total phosphorus is the dependent variable, region is the categorical predictor, and percentage of anthropogenic land use (e.g., cropland, urban land) is the covariate. This allows for the aggregation of regions if there is not a significant regional effect, or if there is a significant regional effect, identifies the need to analyze regions separately. Second, we develop multiple linear regression models with best-model techniques in which anthropogenic land-use classifications are the independent variables, and the logarithms of in-stream nutrient concentrations are the dependent variables. The intercept of these regression models (i.e., expected nutrient concentration in the absence of human activities assuming linear extrapolation to the origin) represents the reference nutrient concentrations. This analysis suggests that larger percentages of cropland and urban land have strong positive influences on in-stream nutrient concentrations, both in eastern Kansas and across the conterminous United States. The most appropriate method for regions may depend on the relative availability of reference sites and other data sources. The covariance/reference approach offers a potential method for regions with limited numbers of reference sites.1 aDodds, W., K.1 aOakes, R. uhttp://129.130.186.12/content/technique-establishing-reference-nutrient-concentrations-across-watersheds-impacted-humans02305nas a2200181 4500008004100000245012700041210006900168300001500237490000700252520163700259100001701896700001801913700001801931700001901949700001601968700001501984856012401999 2003 eng d00aComparing denitrification estimates for a Texas estuary by using acetylene inhibition and membrane inlet mass spectrometry0 aComparing denitrification estimates for a Texas estuary by using a5950 -59560 v693 aCharacterizing denitrification rates in aquatic ecosystems is essential to understanding how systems may respond to increased nutrient loading. Thus, it is important to ensure the precision and accuracy of the methods employed for measuring denitrification rates. The acetylene (C2H2) inhibition method is a simple technique for estimating denitrification. However, potential problems, such as inhibition of nitrification and incomplete inhibition of nitrous oxide reduction, may influence rate estimates. Recently, membrane inlet mass spectrometry (MIMS) has been used to measure denitrification in aquatic systems. Comparable results were obtained with MIMS and C2H2 inhibition methods when chloramphenicol was added to C2H2 inhibition assay mixtures to inhibit new synthesis of denitrifying enzymes. Dissolved-oxygen profiles indicated that surface layers of sediment cores subjected to the MIMS flowthrough incubation remained oxic whereas cores incubated using the C2H2 inhibition methods did not. Analysis of the microbial assemblages before and after incubations indicated significant changes in the sediment surface populations during the long flowthrough incubation for MIMS analysis but not during the shorter incubation used for the C2H2 inhibition method. However, bacterial community changes were also small in MIMS cores at the oxygen transition zone where denitrification occurs. The C2H2 inhibition method with chloramphenicol addition, conducted over short incubation intervals, provides a cost-effective method for estimating denitrification, and rate estimates are comparable to those obtained by the MIMS method.1 aBernot, M.J.1 aDodds, W., K.1 aGardner, W.S.1 aMcCarthy, M.J.1 aSobolev, D.1 aTank, J.L. uhttp://129.130.186.12/content/comparing-denitrification-estimates-texas-estuary-using-acetylene-inhibition-and-membrane02433nas a2200217 4500008004100000245015100041210006900192300001300261490000700274520165000281653002501931653001601956653001701972653001301989653001502002653002502017100002002042700001802062700001702080856011802097 2003 eng d00aEcosystem significance of crayfishes and central stonerollers in a tallgrass prairie stream: Functional differences between co-occurring omnivores0 aEcosystem significance of crayfishes and central stonerollers in a423 -4410 v223 aThe ecosystem significance of crayfishes (Orconectes nais (Faxon) and O. neglectus (Faxon)) and central stoneroller minnows (Campostoma anomalum (Rafinesque)), was examined in a tallgrass prairie stream by estimating the trophic basis of production and consumption for each species. Annual ash-free dry mass production and production to biomass ratios of C. anomalum (260 mg m−2 y−1, 1.3) were lower than that of O. nais (719 mg m−2 y−1, 2.4) and O. neglectus (508 mg m−2 y−1, 2.1). Gut content analysis revealed no significant differences in the percentages of the various food items ingested by O. nais and O. neglectus, indicating they were functionally similar with respect to the types of organic matter processed in this system. We found a significant difference among seasons in the % of invertebrates in C. anomalum guts (p = 0.0001) and the % of algae in Orconectes spp. guts (p = 0.005), indicating the importance of measuring resource use throughout the growing season. Leaves contributed most to Orconectes spp. annual production (45%) followed by animal matter (30%), algae (19%), and amorphous detritus (6%). Algae contributed most to C. anomalum production (47%) followed by amorphous detritus (30%), animal matter (21%), and leaves (2%). Orconectes spp. consumed more leaf litter, filamentous green algae, and macroinvertebrates than C. anomalum, whereas C. anomalum consumed more diatoms. Crayfish and central stonerollers are both omnivores that function as important consumers and processors of algae and detritus in this tallgrass prairie stream, but each focuses on slightly different types of similar resources.10acentral stonerollers10aGrowth rate10agut contents10aomnivory10aOrconectes10asecondary production1 aEvans-White, M.1 aDodds, W., K.1 aWhiles, M.R. uhttp://129.130.186.12/content/ecosystem-significance-crayfishes-and-central-stonerollers-tallgrass-prairie-stream02609nas a2200337 4500008004100000245007800041210006900119300001500188490000700203520162900210100001801839700001901857700001501876700001701891700001801908700001901926700001701945700001501962700002001977700001801997700001602015700001902031700001802050700001402068700001902082700001602101700001802117700001702135700001902152856010002171 2003 eng d00aFactors affecting ammonium uptake in streams - an inter-biome perspective0 aFactors affecting ammonium uptake in streams an interbiome persp a1329 -13520 v483 a1. The Lotic Intersite Nitrogen eXperiment (LINX) was a coordinated study of the relationships between North American biomes and factors governing ammonium uptake in streams. Our objective was to relate inter-biome variability of ammonium uptake to physical, chemical and biological processes. 2. Data were collected from 11 streams ranging from arctic to tropical and from desert to rainforest. Measurements at each site included physical, hydraulic and chemical characteristics, biological parameters, whole-stream metabolism and ammonium uptake. Ammonium uptake was measured by injection of 15N-ammonium and downstream measurements of 15N-ammonium concentration. 3. We found no general, statistically significant relationships that explained the variability in ammonium uptake among sites. However, this approach does not account for the multiple mechanisms of ammonium uptake in streams. When we estimated biological demand for inorganic nitrogen based on our measurements of in-stream metabolism, we found good correspondence between calculated nitrogen demand and measured assimilative nitrogen uptake. 4. Nitrogen uptake varied little among sites, reflecting metabolic compensation in streams in a variety of distinctly different biomes (autotrophic production is high where allochthonous inputs are relatively low and vice versa). 5. Both autotrophic and heterotrophic metabolism require nitrogen and these biotic processes dominate inorganic nitrogen retention in streams. Factors that affect the relative balance of autotrophic and heterotrophic metabolism indirectly control inorganic nitrogen uptake.1 aWebster, J.R.1 aMulholland, P.1 aTank, J.L.1 aValett, H.M.1 aDodds, W., K.1 aPeterson, B.J.1 aBowden, W.B.1 aDahm, C.N.1 aFindlay, S.E.G.1 aGregory, S.V.1 aGrimm, N.B.1 aHamilton, S.K.1 aJohnson, S.L.1 aMarti, E.1 aMcDowell, W.H.1 aMeyer, J.L.1 aMorrall, D.D.1 aThomas, S.A.1 aWollheim, W.M. uhttp://129.130.186.12/content/factors-affecting-ammonium-uptake-streams-inter-biome-perspective02214nas a2200205 4500008004100000245011000041210006900151300001300220490000700233520147600240653001301716653003401729653002401763653001201787653002401799653001401823653002901837100001801866856012401884 2003 eng d00aMisuse of inorganic N and soluble reactive P concentrations to indicate nutrient status of surface waters0 aMisuse of inorganic N and soluble reactive P concentrations to i a171 -1810 v223 aDissolved inorganic N (DIN) and soluble reactive P (SRP) have been used by some to indicate the trophic status of waters, and concentration ratios (DIN:SRP) to indicate nutrient deficiency. The utility of such measurements should be questioned, particularly based on well-known problems associated with determination of the concentration of SRP, which is commonly assumed to represent PO43−. Another potential problem with using inorganic nutrient pools to represent trophic state and nutrient availability ratios arises because concentration values are in units of mass per unit volume, and cannot be used with certainty to estimate supply (i.e., turnover rate of the nutrient pool, expressed either in mass per unit volume per unit time or simply as per unit time) to organisms without information on uptake and remineralization. Two data sets with lotic water-column nutrient values were explored, a large, continental-scale data set with analyses and collections done by many laboratories, and a more limited data set collected and analyzed by the same laboratory. In concert, the data sets indicated that at high total N (TN) (i.e., >5 mg/L) and total P (TP) (i.e., >2 mg/L) concentrations, >60% of the nutrient is usually made up of dissolved inorganic forms, but at low levels the ratio of dissolved inorganic to total nutrients is highly variable. Last, DIN:SRP is a weak surrogate for TN:TP and thus should be used with caution to indicate nutrient limitation.10aammonium10adissolved reactive phosphorus10ainorganic nutrients10aNitrate10anutrient limitation10aphosphate10awater-quality monitoring1 aDodds, W., K. uhttp://129.130.186.12/content/misuse-inorganic-n-and-soluble-reactive-p-concentrations-indicate-nutrient-status-surface02463nas a2200133 4500008004100000245008400041210006900125300001500194490000700209520197500216100001502191700001802206856010502224 2003 eng d00aResponses of heterotrophic and autotrophic biofilms to nutrients in ten streams0 aResponses of heterotrophic and autotrophic biofilms to nutrients a1031 -10490 v483 a1. Nutrient diffusing substrata were used to determine the effect of added inorganic nitrogen (N) and phosphorus (P) on the development of epilithic and epixylic biofilms in 10 North American streams. Four treatments of diffusing substrata were used: Control (agar only), N addition (0.5 m NaNO3), P addition (0.5 m KH2PO4), and N + P combined (0.5 m NaNO3 + 0.5 m KH2PO4). Agar surfaces were covered with glass fibre filters (for epilithon) or discs of untreated white oak wood veneer (for epixylon). 2. We found that if algae showed significant response to nutrient addition, N limitation (either N alone or N with P) was the most frequent response both on GF/F filters and on wood. Despite the low dissolved nutrient concentrations in our study streams, more than a third of the streams did not show any response to N or P addition. In fact, P was never the sole limiting nutrient for algal biofilms in this study. 3. Nutrient addition influenced algal colonisation of inorganic versus organic substrata in different ways. The presence of other biofilm constituents (e.g. fungi or bacteria) may influence whether algal biomass on wood increased in response to nutrient addition. Algae on organic and inorganic substrata responded similarly to nutrient addition in only one stream. 4. Fungal biomass on wood was nutrient limited in six of 10 study streams. N limitation of fungal biomass (with or without secondary P limitation) was most frequent, but P limitation did occur in two streams. 5. Our results show that biomass responses to nutrient addition by the heterotrophic and autotrophic components of the epixylic biofilm were different, though both experienced the same stream nutrient conditions. For algae and fungi growing on wood, limiting nutrients were rarely similar. Only three of nine streams showed the same biomass response to nutrient addition, including two that showed no significant change in biomass despite added nutrients.1 aTank, J.L.1 aDodds, W., K. uhttp://129.130.186.12/content/responses-heterotrophic-and-autotrophic-biofilms-nutrients-ten-streams02205nas a2200217 4500008004100000245008900041210006900130300001300199490000700212520150300219653001901722653001501741653002201756653001501778653001401793653001501807653002301822653001801845100001801863856010601881 2003 eng d00aThe role of periphyton in phosphorus retention in shallow freshwater aquatic systems0 arole of periphyton in phosphorus retention in shallow freshwater a830 -8490 v393 a

Eutrophication caused by phosphorus (P) leads to water quality problems in aquatic systems, particularly freshwaters, worldwide. Processing of nutrients in shallow habitats removes P from water naturally and periphyton influences P removal from the water column in flowing waters and wetlands. Periphyton plays several roles in removing P from the water column, including P uptake and deposition, filtering particulate P from the water, and attenuating flow, which decreases advective transport of particulate and dissolved P from sediments. Furthermore, periphyton photosynthesis locally increases pH by up to 1 unit, which can lead to increased precipitation of calcium phosphate, concurrent deposition of carbonate-phosphate complexes, and long-term burial of P. Actively photosynthesizing periphyton can cause super-saturated O2 concentrations near the sediment surface encouraging deposition of metal phosphates. However, anoxia associated with periphyton respiration at night may offset this effect. Linking the small-scale functional role of periphyton to ecosystem-level P retention will require more detailed studies in a variety of ecosystems or large mesocosms. A case study from the Everglades illustrates the importance of considering the role of periphyton in P removal from wetlands. In general, periphyton tends to increase P retention and deposition. In pilot-scale constructed periphyton-dominated wetlands in South Florida, about half of the inflowing total P was removed.

10aeutrophication10amicroalgae10amicrophytobenthos10aperiphyton10aphosphate10aPhosphorus10atertiary treatment10awater quality1 aDodds, W., K. uhttp://129.130.186.12/content/role-periphyton-phosphorus-retention-shallow-freshwater-aquatic-systems02844nas a2200373 4500008004100000245012600041210006900167300001300236490000700249520170000256653001301956653002401969653002101993653002302014653001102037653001802048100002102066700001502087700001802102700001702120700001802137700001802155700001602173700001902189700001802208700001402226700001902240700001602259700001602275700001902291700001702310700001902327856012402346 2002 eng d00aCan uptake length in streams be determined by nutrient addition experiments? Results from an inter-biome comparison study0 aCan uptake length in streams be determined by nutrient addition  a544 -5600 v213 aNutrient uptake length is an important parameter for quantifying nutrient cycling in streams. Although nutrient tracer additions are the preferred method for measuring uptake length under ambient nutrient concentrations, short-term nutrient addition experiments have more frequently been used to estimate uptake length in streams. Theoretical analysis of the relationship between uptake length determined by nutrient addition experiments (SW′) and uptake length determined by tracer additions (SW) predicted that SW′ should be consistently longer than SW, and that the overestimate of uptake length by SW′ should be related to the level of nutrient addition above ambient concentrations and the degree of nutrient limitation. To test these predictions, we used data from an interbiome study of NH4+ uptake length in which 15NH4+ tracer and short-term NH4+ addition experiments were performed in 10 streams using a uniform experimental approach. The experimental results largely confirmed the theoretical predictions: SW′ was consistently longer than SW and SW′:SW ratios were directly related to the level of NH4+ addition and to indicators of N limitation. The experimentally derived SW′:SW ratios were used with the theoretical results to infer the N limitation status of each stream. Together, the theoretical and experimental results showed that tracer experiments should be used whenever possible to determine nutrient uptake length in streams. Nutrient addition experiments may be useful for comparing uptake lengths between different streams or different times in the same stream, however, provided that nutrient additions are kept as low as possible and of similar magnitude.10aammonium10anitrogen limitation10anutrient cycling10anutrient spiraling10astream10auptake length1 aMulholland, P.J.1 aTank, J.L.1 aWebster, J.R.1 aBowden, W.B.1 aDodds, W., K.1 aGregory, S.V.1 aGrimm, N.B.1 aHamilton, S.K.1 aJohnson, S.L.1 aMarti, E.1 aMcDowell, W.H.1 aMerriam, J.1 aMeyer, J.L.1 aPeterson, B.J.1 aValett, H.M.1 aWollheim, W.M. uhttp://129.130.186.12/content/can-uptake-length-streams-be-determined-nutrient-addition-experiments-results-inter-biome03019nas a2200169 4500008004100000245010200041210006900143300001400212490000700226520241600233653001802649653001202667653001102679100001502690700001802705856012602723 2002 eng d00aComparisons of nitrification and denitrification in prairie and agriculturally influenced streams0 aComparisons of nitrification and denitrification in prairie and  a998 -10090 v123 aWhole-stream nitrification and denitrification rates were calculated from field incubation studies of representative substrata in Kings Creek and Shane Creek watersheds at the Konza Prairie Biological Station, Kansas, USA. Substrata from a relatively pristine upstream and an agriculturally influenced downstream reach were measured in both watersheds. Rates were scaled to the whole stream by the mass of each substratum in the stream reach. Substrata sampled included epilithon, leaf packs and wood (coarse benthic organic matter, CBOM), filamentous green algae, bryophytes, fine benthic organic matter (FBOM), and suspended particulate organic matter. Upstream sites had significantly lower nitrification and denitrification rates than downstream sites. Nitrification rates were dominated by nitrification associated with epilithon and filamentous green algae. Downstream sites had a higher proportion of nitrification occurring in the water column relative to upstream sites. Whole-stream denitrification was dominated by denitrification associated with FBOM and CBOM and was higher downstream. Water column ammonium (NH4+) and nitrate (NO3−) concentrations were correlated with whole-stream nitrification rates but not whole-stream denitrification rates. Whole-stream nitrification rates were positively correlated with whole-stream denitrification rates, being coupled at the whole-stream level, but not at the substratum level. Relative to the amount of NO3− produced through nitrification, the proportion of NO3− denitrified was 1.4–4.6 times greater in the downstream sites compared to the upstream sites, but the proportion of the in-stream NO3− load denitrified was ∼10 times greater in the upstream sites. These data indicate that changes in stream nitrogen cycling related to increased dissolved inorganic nitrogen concentrations do not result in a large enough increase in denitrification (the stream's capacity to retain nitrogen) to compensate for the increased nitrogen loading. Data also suggest that whole-stream nitrification and denitrification may be decoupled at the reach level by factors that decrease habitat heterogeneity (the variety of substrata types) in stream channels. This indicates that anthropogenic disturbances of small streams, such as channelization and removal of riparian vegetation, would be expected to decrease the capacity of streams to retain nitrogen.10anitrification10aprairie10astream1 aKemp, M.J.1 aDodds, W., K. uhttp://129.130.186.12/content/comparisons-nitrification-and-denitrification-prairie-and-agriculturally-influenced-streams00768nas a2200229 4500008004100000245010100041210006900142300001100211490000700222100002000229700001300249700001200262700001800274700002100292700001900313700001600332700001900348700001600367700001800383700001700401856012000418 2002 eng d00aA cross-system comparison of bacterial and fungal biomass in detritus pools of headwater streams0 acrosssystem comparison of bacterial and fungal biomass in detrit a55 -660 v431 aFindlay, S.E.G.1 aTank, J.1 aDye, S.1 aVallett, H.M.1 aMulholland, P.J.1 aMcDowell, W.H.1 aJohnson, S.1 aHamilton, S.K.1 aEdmonds, J.1 aDodds, W., K.1 aBowden, W.B. uhttp://129.130.186.12/content/cross-system-comparison-bacterial-and-fungal-biomass-detritus-pools-headwater-streams02693nas a2200133 4500008004100000245016800041210006900209300001500278490000700293520210500300100001502405700001802420856012102438 2002 eng d00aThe influence of ammonium, nitrate, and dissolved oxygen concentration on uptake, nitrification, and denitrification rates associated with prairie stream substrata0 ainfluence of ammonium nitrate and dissolved oxygen concentration a1380 -13930 v473 a

Substrata samples were collected from Kings Creek on Konza Prairie Biological Station (Manhattan, Kansas) and incubated with varying levels of ammonium (NH4+), nitrate (NO3−), and dissolved oxygen (O2) to examine the response of nitrogen (N) uptake and transformation rates. Substrata collected were fine benthic organic matter (FBOM), coarse benthic organic matter, filamentous green algae, bryophytes, suspended particulate organic matter, and epilithic diatoms. Nitrification and denitrification were estimated by use of the nitrapyrin and acetylene inhibition methods, respectively. Ammonium uptake demonstrated Michaelis-Menten kinetics, with the highest maximum rates (Vmax) associated with filamentous green algae (5.90 mg N gdm−1 d−1) and epilithic diatoms (4.96 mg N gdm−1 d−1). Nitrate uptake did not saturate at the highest NO3− addition (25 µg N L−1) above ambient when associated with FBOM. Overall, maximum uptake rates of NH4+ were 10-fold higher than for NO3−. Nitrification response to increasing NH4+ concentrations was highly variable, depending on the substrata type. Nitrification was lowest under low O2 conditions, being undetectable when NO3− was added but not when NH4+ was added. Denitrification increased linearly with NO3− concentration when associated with epilithic diatoms and FBOM but became saturated at ~20 µg N L−1 above ambient concentrations when associated with filamentous green algae. Samples purged with N2 gas had the highest rates of denitrification. We predicted stream ecosystem rates using equations derived from the experimental data and substrata mass estimates measured in the field. Substantial temporal variability was predicted in uptake (0–1,300 mg NH4+−N m−2 d−1; 0–5.2 mg NO3−−N m−2 d−1), nitrification (0–35 mg NH4+−N m−2 d−1), and denitrification (0–130 µg N2O-N m−2 d−1) as due to natural variation in water column NH4+, NO3−, and O2 concentrations.

1 aKemp, M.J.1 aDodds, W., K. uhttp://129.130.186.12/content/influence-ammonium-nitrate-and-dissolved-oxygen-concentration-uptake-nitrification-and01925nas a2200145 4500008004100000245008700041210006900128300001200197490000800209520144800217653002201665100001601687700001801703856005801721 2002 eng d00aMacroinvertebrate assemblage structure across a tallgrass prairie stream landscape0 aMacroinvertebrate assemblage structure across a tallgrass prairi a70 -1020 v1543 aStream macroinvertebrates were collected from four intermittent tributaries and two perennial sites within the Kings Creek basin, Konza Prairie Biological Station (KPBS) near Manhattan, KS, USA. The objectives of this study were to assess the roles of disturbances (floods and drying) and refugia on benthic and colonization (drift and aerial) assemblage composition over two years among sites with contrasting hydrologic regimes. Benthic taxa richness and diversity at the perennial headwater site were significantly greater than richness and diversity at intermittent sites, whereas the downstream perennial site did not differ significantly from two of the intermittent sites. The larger magnitude of floods at the downstream perennial site resulted in greater losses in richness than at the upstream intermittent and perennial sites. Both classification and ordination revealed that benthic assemblage composition was more strongly correlated with time since last disturbance and season than with static hydrologic descriptors, microhabitat measures, or assemblage characteristics (richness or density). Richness of aerial colonization and drift samples collected at intermittent sites was greatest at the site with the nearest upstream perennial surface water. Because Kings Creek is a relatively pristine stream, these data may be useful as a baseline for comparison with future efforts for bioassessment of intermittent prairie streams.10atallgrass prairie1 aFritz, K.M.1 aDodds, W., K. uhttp://cat.inist.fr/?aModele=afficheN&cpsidt=1366523903297nas a2200409 4500008004100000245005500041210005500096300001300151490000700164520221800171653002402389653001302413653001702426653001202443653001302455653001902468653001202487653001302499100001802512700001702530700001702547700001602564700001602580700001902596700001802615700001402633700001902647700001602666700001602682700002102698700001902719700001502738700002502753700001802778700001702796856007402813 2002 eng d00aN uptake as a function of concentration in streams0 aN uptake as a function of concentration in streams a206 -2200 v213 aDetailed studies of stream N uptake were conducted in a prairie reach and gallery forest reach of Kings Creek on the Konza Prairie Biological Station. Nutrient uptake rates were measured with multiple short-term enrichments of NO3− and NH4+ at constant addition rates in the spring and summer of 1998. NH4+ uptake was also measured with 15N-NH4+ tracer additions and short-term unlabeled NH4+ additions at 12 stream sites across North America. Concurrent addition of a conservative tracer was used to account for dilution in all experiments. NH4+ uptake rate per unit area (Ut) was positively correlated to nutrient concentration across all sites (r2 = 0.41, log–log relationship). Relationships between concentration and Ut were used to determine whether the uptake was nonlinear (i.e., kinetic uptake primarily limited by the biotic capacity of microorganisms to accumulate nutrients) or linear (e.g., limited by mass transport into stream biofilms). In all systems, Ut was lower at ambient concentrations than at elevated concentrations. Extrapolation from uptake measured from a series of increasing enrichments could be used to estimate ambient Ut. Linear extrapolation of Ut assuming the relationship passes through the origin and rates measured at 1 elevated nutrient concentration underestimated ambient Ut by ∼3-fold. Uptake rates were saturated under some but not all conditions of enrichment; in some cases there was no saturation up to 50 μmol/L. The absolute concentration at which Ut was saturated in Kings Creek varied among reaches and nutrients. Uptake rates of NH4+ at ambient concentrations in all streams were higher than would be expected, assuming Ut does not saturate with increasing concentrations. At ambient nutrient concentrations in unpolluted streams, Ut is probably limited to some degree by the kinetic uptake capacity of stream biota. Mass transfer velocity from the water column is generally greater than would be expected given typical diffusion rates, underscoring the importance of advective transport. Given the short-term spikes in nutrient concentrations that can occur in streams (e.g., in response to storm events), Ut may not saturate, even at high concentrations.10aadvective transport10aammonium10aareal uptake10abenthos10akinetics10amass transport10aNitrate10anitrogen1 aDodds, W., K.1 aLópez, A.J.1 aBowden, W.B.1 aGregory, S.1 aGrimm, N.B.1 aHamilton, S.K.1 aHershey, A.E.1 aMarti, E.1 aMcDowell, W.B.1 aMeyer, J.L.1 aMorrall, D.1 aMulholland, P.J.1 aPeterson, B.J.1 aTank, J.L.1 avan der Hoek, D.C.J.1 aWebster, J.R.1 aWollheim, W. uhttp://129.130.186.12/content/n-uptake-function-concentration-streams01984nas a2200145 4500008004100000245008800041210006900129300001300198490000700211520145900218100001801677700001601695700001501711856011201726 2002 eng d00aNitrogen and phosphorus relationships to benthic algal biomass in temperate streams0 aNitrogen and phosphorus relationships to benthic algal biomass i a865 -8740 v593 aKnowledge of factors limiting benthic algal (periphyton) biomass is central to understanding energy flow in stream ecosystems and stream eutrophication. We used several data sets to determine how water column nutrients and nonnutrient factors are linked to periphytic biomass and if the ecoregion concept is applicable to nutrient–periphyton relationships. Literature values for seasonal means of biomass of periphyton, nutrient concentrations, and other stream characteristics were collected for almost 300 sampling periods from temperate streams. Data for benthic chlorophyll and nutrient concentrations from a subset of 620 stations in the United States National Stream Water-Quality Monitoring Networks were also analyzed. The greatest portion of variance in models for the mean and maximum biomass of benthic stream algae (about 40%) was explained by concentrations of total N and P. Breakpoint regression and a two-dimensional Kolmogorov–Smirnov statistical technique established significant breakpoints of about 30 µg total P·L–1 and 40 µg total N·L–1, above which mean chlorophyll values were substantially higher. Ecoregion effects on nutrient–chlorophyll relationships were weak. Ecoregion effects were cross-correlated with anthropogenic effects such as percent urban and cropland area in the watershed and population density. Thus, caution is necessary to separate anthropogenic effects from natural variation at the ecoregion level.1 aDodds, W., K.1 aSmith, V.H.1 aLohman, K. uhttp://129.130.186.12/content/nitrogen-and-phosphorus-relationships-benthic-algal-biomass-temperate-streams02477nas a2200133 4500008004100000245013300041210006900174300001500243490000700258520191700265100001702182700001802199856012602217 2002 eng d00aRelationships between stream size, suspended particles, and filter-feeding macroinvertebrates in a Great Plains drainage network0 aRelationships between stream size suspended particles and filter a1589 -16000 v313 aSuspended fine particles (seston) are an important component of energy and nutrient cycling in streams, but they can also be pollutants. We examined seston dynamics and filter-feeding macroinvertebrate communities in sites representing headwaters to large rivers in the Kansas River drainage, northeastern KS. Seston samples were collected at least seasonally during low to moderate flows for one year beginning in the summer of 1999, and quality was assessed by determining organic content and C to N ratio. A rapid bioassessment approach was used to examine filter-feeders. Relationships between stream size and seston concentrations were markedly influenced by anthropogenic activities. There was no relationship between total seston concentration and stream size across all sites (r = 0.14, p > 0.05), but a significant, positive relationship was evident when impounded and suburban sites were excluded (r = 0.73, p < 0.01); this same trend was evident for organic and inorganic components. Seasonal patterns of C to N ratio were evident, with generally lower values during winter and highest values in summer. However, seasonal patterns were dampened in suburban sites and virtually absent below impoundments. Filter-feeder richness was correlated with average organic seston concentrations (r = 0.8, p < 0.01), but this relationship was also obscured by impoundments and suburban development. In particular, impoundments had a dramatic, negative effect on richness. Abundance of most hydropsychid caddisfly taxa was positively correlated with organic seston concentration. Results indicate there are significant patterns regarding seston, filter-feeders, and stream size in this Great Plains river system, but patterns are strongly influenced by human activities. These relationships are relevant to management issues regarding suspended particles and the potential development of bioassessment techniques.1 aWhiles, M.R.1 aDodds, W., K. uhttp://129.130.186.12/content/relationships-between-stream-size-suspended-particles-and-filter-feeding-macroinvertebrates02324nas a2200217 4500008004100000245011200041210006900153300001000222490000700232520159700239653001001836653001201846653000901858653001801867653002201885653002201907653002101929100001801950700001801968856012001986 2002 eng d00aWater velocity attenuation by stream periphyton and macrophytes in relation to growth form and architecture0 aWater velocity attenuation by stream periphyton and macrophytes  a2 -150 v213 aPeriphyton and macrophytes alter water velocity in streams, influencing movement of solutes and providing microhabitat for other organisms. How assemblages with different growth form and architecture influence water velocity attenuation across mm to dm scales is not well described. A thermistor microprobe was used to measure water velocity through 4 morphologically distinct stream periphyton assemblages and 4 distinct stream macrophyte assemblages in flumes. All assemblages resulted in an exponential decay in velocity with depth. A dense assemblage of diatoms (primarily Cymbella) attenuated velocity more than filamentous green algae, filamentous green algae with interspersed diatoms, or a red alga (ANOVA, p < 0.05). External water velocity had no significant influence on the coefficient of attenuation in a filamentous green alga (ANOVA, p = 0.76). Macrophytes also attenuated water velocity, but attenuation was more variable and, in all cases, attenuation coefficients were less for macrophytes than for periphyton. A model unifying attenuation by periphyton and macrophytes was developed using biomass density (g ash-free dry mass/m3) as the independent variable and it explained 80% of the variation in attenuation. The relative variance of attenuation coefficients increased sharply as Reynolds number increased above ∼500 to 700, suggesting that variance in water velocity was dependent upon the spatial scale of the primary producer through which water is flowing, and that the distinction btween periphyton and macrophytes may have real physical ramifications.10aAlgae10aCurrent10aFlow10aHydrodynamics10amicrophytobenthos10aPrimary producers10aSubmerged plants1 aDodds, W., K.1 aBiggs, B.J.F. uhttp://129.130.186.12/content/water-velocity-attenuation-stream-periphyton-and-macrophytes-relation-growth-form-and01971nas a2200217 4500008004100000245010800041210006900149300001300218490000700231520124600238653001001484653002001494653001401514653001801528653002101546653001201567653002201579100001501601700001801616856011901634 2001 eng d00aCentimeter-scale patterns of oxygen concentrations related to nitrification in prairie stream substrate0 aCentimeterscale patterns of oxygen concentrations related to nit a347 -3570 v203 aDissolved oxygen (O2) was measured with microelectrodes in shallow subsurface microsites in a prairie stream and related to rates of nitrification determined in the laboratory using the nitrapyrin method. Substrata sampled included diatom mats, leaves and wood (coarse benthic organic matter, CBOM), filamentous green algae, bryophytes, and fine benthic organic matter (FBOM). Significant differences in O2 concentrations were found among the substrata, with anoxic zones occurring primarily in FBOM from deep pool sediments and CBOM from litter accumulations. Filamentous green algae and bryophytes had average O2 concentrations near saturation and intermediate rates of nitrification. Diatom mats had the highest concentrations of O2 (up to several times saturation) and the highest rates of nitrification. In the summer, O2 concentrations were above saturation in epilithon and filamentous green algal mats. Nitrification rates were highest in epilithon and filamentous green algae samples taken in the spring and autumn. A significant positive relationship between nitrification rates and O2 concentration was observed in all seasons except summer. These data suggest that O2 concentration could control nitrification in prairie streams.10aAlgae10amicroelectrodes10aN cycling10anitrification10aO2 concentration10astreams10atallgrass prairie1 aKemp, M.J.1 aDodds, W., K. uhttp://129.130.186.12/content/centimeter-scale-patterns-oxygen-concentrations-related-nitrification-prairie-stream03108nas a2200217 4500008004100000245021100041210006900252300001300321490000800334520227400342653001402616653001702630653001402647653001302661653002002674100002202694700001802716700001302734700001602747856012702763 2001 eng d00aA comparison of the trophic ecology of crayfish (Orconectes nais (Faxon) and Orconectes neglectus (Faxon)) and central stonerollers (Compostoma anomalum (Rafinesque)): omnivory in a tallgrass prairie stream0 acomparison of the trophic ecology of crayfish Orconectes nais Fa a131 -1440 v4623 aOmnivorous fish, such as the central stoneroller minnow (Campostoma anomalum(Rafinesque)), and crayfish often play important roles in the trophic dynamics of streams. The trophic role of these two omnivores has not been compared within a system even though they both consume algae, detritus and invertebrates and often co-occur in streams in the Midwestern United States. Natural abundance of 15N and 13C isotopes and a whole stream 15N-labeled ammonium chloride release were used to compare the trophic ecology of the central stoneroller minnow (Campostoma anomalum (Rafinesque)) and two species of crayfish (Orconectes neglectus (Faxon) and Orconectes nais (Faxon)) in a tallgrass prairie stream. The δ15N and δ13C values of Orconectes spp. were more similar to coarse benthic organic matter (CBOM) and filamentous green algae than to invertebrates, fine benthic organic matter (FBOM), and periphyton. Values for δ15N and δ13C in C. anomalum were more similar to grazer and collector invertebrates and filamentous green algae than to FBOM and periphyton. Results from a 15N tracer release also indicated a portion of algae and/or invertebrates were a component of nitrogen assimilated in Orconectes spp. and C. anomalum diets. Gut contents of C. anomalum were also analyzed. In contrast to stable isotope data, amorphous detritus was a significant component of C. anomalum guts, followed by diatoms and filamentous green algae. A significant percentage of invertebrate material was found in C. anomalum guts sampled in the spring. Experiments were conducted in artificial streams to determine if Orconectes spp. and C. anomalum could reduce epilithic algal biomass in small streams. Algal biomass on clay tile substrata was decreased relative to controls in artificial stream channels containing O. neglectus (3.4 fold, p=0.0002), C. anomalum (2.1 fold, p=0.0012), and both species combined (3.0 fold, p=0.0003). Results indicate that Orconectes spp. are functioning more as algal and detrital processors than as predators in Kings Creek. Isotope and gut content data show that C. anomalum includes invertebrates as well as algae and detritus in its diet. Both species have the potential to affect algal biomass and are important omnivores in the stream food web.10afood webs10agut analysis10aHerbivory10aomnivory10aStable isotopes1 aEvans-White, M.A.1 aDodds, W., K.1 aGray, L.1 aFritz, K.M. uhttp://129.130.186.12/content/comparison-trophic-ecology-crayfish-orconectes-nais-faxon-and-orconectes-neglectus-faxon-and01723nas a2200289 4500008004100000245006800041210006800109300001100177490000800188520088600196100001901082700001901101700002101120700001801141700001601159700001501175700001401190700001701204700001701221700001801238700001901256700001801275700001901293700001601312700001801328856008701346 2001 eng d00aControl of nitrogen export from watersheds by headwater streams0 aControl of nitrogen export from watersheds by headwater streams a86 -900 v2923 aA comparative 15N-tracer study of nitrogen dynamics in headwater streams from biomes throughout North America demonstrates that streams exert control over nutrient exports to rivers, lakes, and estuaries. The most rapid uptake and transformation of inorganic nitrogen occurred in the smallest streams. Ammonium entering these streams was removed from the water within a few tens to hundreds of meters. Nitrate was also removed from stream water but traveled a distance 5 to 10 times as long, on average, as ammonium. Despite low ammonium concentration in stream water, nitrification rates were high, indicating that small streams are potentially important sources of atmospheric nitrous oxide. During seasons of high biological activity, the reaches of headwater streams typically export downstream less than half of the input of dissolved inorganic nitrogen from their watersheds.1 aPeterson, B.J.1 aWollheim, W.M.1 aMulholland, P.J.1 aWebster, J.R.1 aMeyer, J.L.1 aTank, J.L.1 aMarti, E.1 aBowden, W.B.1 aValett, H.M.1 aHershey, A.E.1 aMcDowell, W.H.1 aDodds, W., K.1 aHamilton, S.K.1 aGregory, S.1 aMorrall, D.D. uhttp://129.130.186.12/content/control-nitrogen-export-watersheds-headwater-streams02732nas a2200265 4500008004100000245006800041210006700109300001500176490000700191520194500198100002102143700001802164700001502182700001602197700001802213700001902231700001402250700001902264700001702283700001802300700001902318700001502337700001902352856009502371 2001 eng d00aInter-biome comparison of factors controlling stream metabolism0 aInterbiome comparison of factors controlling stream metabolism a1503 -15170 v463 a1. We studied whole-ecosystem metabolism in eight streams from several biomes in North America to identify controls on the rate of stream metabolism over a large geographic range. The streams studied had climates ranging from tropical to cool-temperate and from humid to arid and were all relatively uninfluenced by human disturbances. 2. Rates of gross primary production (GPP), ecosystem respiration (R) and net ecosystem production (NEP) were determined using the open-system, two-station diurnal oxygen change method. 3. Three general patterns in metabolism were evident among streams: (1) relatively high GPP with positive NEP (i.e. net oxygen production) in early afternoon, (2) moderate primary production with a distinct peak in GPP during daylight but negative NEP at all times and (3) little or no evidence of GPP during daylight and a relatively constant and negative NEP over the entire day. 4. Gross primary production was most strongly correlated with photosynthetically active radiation (PAR). A multiple regression model that included log PAR and stream water soluble reactive phosphorus (SRP) concentration explained 90% of the variation in log GPP. 5. Ecosystem respiration was significantly correlated with SRP concentration and size of the transient storage zone and, together, these factors explained 73% of the variation in R. The rate of R was poorly correlated with the rate of GPP. 6. Net ecosystem production was significantly correlated only with PAR, with 53% of the variation in log NEP explained by log PAR. Only Sycamore Creek, a desert stream in Arizona, had positive NEP (GPP: R > 1), supporting the idea that streams are generally net sinks rather than net sources of organic matter. 7. Our results suggest that light, phosphorus concentration and channel hydraulics are important controls on the rate of ecosystem metabolism in streams over very extensive geographic areas.1 aMulholland, P.J.1 aFellows, C.S.1 aTank, J.L.1 aGrimm, N.B.1 aWebster, J.R.1 aHamilton, S.K.1 aMarti, E.1 aAshkenas, L.R.1 aBowden, W.B.1 aDodds, W., K.1 aMcDowell, W.H.1 aPaul, M.J.1 aPeterson, B.J. uhttp://129.130.186.12/content/inter-biome-comparison-factors-controlling-stream-metabolism02884nas a2200205 4500008004100000245012000041210006900161300001300230490000700243520216800250653001302418653001602431653001202447653002102459653002602480653001202506100001502518700001802533856012702551 2001 eng d00aSpatial and temporal patterns of nitrogen concentrations in pristine and agriculturally- influenced prairie streams0 aSpatial and temporal patterns of nitrogen concentrations in pris a125 -1410 v533 aLong-term data on nitrogen chemistry of streams draining Konza Prairie Biological Station (Konza), Kansas were analyzed to assess spatial and temporal patterns and examine the influence of agricultural activity on these patterns. Upland watersheds of Konza are predominantly tallgrass prairies, but agricultural fields and riparian forests border the lower reaches of the streams. We have up to 11 years of data in the relatively pristine upland reaches and 4 years of data on wells and downstream reaches influenced by fertilized croplands. Seasonal and spatial patterns in total nitrogen (TN) concentrations were driven largely by changes in the nitrate (NO3 −) concentrations. A gradient of increasing NO3 − concentrations occurred from pristine upland stream reaches to the more agriculturally-influenced lowland reaches. Nitrate concentrations varied seasonally and were negatively correlated with discharge in areas influenced by row-crop agriculture (p = 0.007). The NO3 − concentrations of stream water in lowland reaches were lowest during times of high precipitation, when the relative influence of groundwater drainage is minimal and water in the channel is primarily derived from upland prairie reaches. The groundwater from cropland increased stream NO3 − concentrations about four-fold during low-discharge periods, even though significant riparian forest corridors existed along most of the lower stream channel. The minimum NO3 − concentrations in the agriculturally influenced reaches were greater than at any time in prairie reaches. Analysis of data before and after introduction of bison to four prairie watersheds revealed a 35% increase of TN concentrations (p < 0.05) in the stream water channels after the introduction of bison. These data suggest that natural processes such as bison grazing, variable discharge, and localized input of groundwater lead to variation in NO3 − concentrations less than 100-fold in prairie streams. Row-crop agriculture can increase NO3 − concentrations well over 100-fold relative to pristine systems, and the influence of this land use process over space and time overrides natural processes.10aammonium10agroundwater10aNitrate10anutrient cycling10ariparian buffer zones10astreams1 aKemp, M.J.1 aDodds, W., K. uhttp://129.130.186.12/content/spatial-and-temporal-patterns-nitrogen-concentrations-pristine-and-agriculturally-influenced00380nas a2200121 4500008004100000245004600041210004600087300001300133490000700146100001800153700001400171856007300185 2000 eng d00aEstablishing nutrient criteria in streams0 aEstablishing nutrient criteria in streams a186 -1960 v191 aDodds, W., K.1 aWelch, E. uhttp://129.130.186.12/content/establishing-nutrient-criteria-streams02545nas a2200325 4500008004100000245006100041210006100102300001300163490000600176520164900182653002001831653001401851653001901865653002001884653001101904653002201915100001801937700002201955700001801977700001301995700001702008700001502025700001702040700001802057700001602075700001502091700001702106700001702123856007902140 2000 eng d00aQuantification of the nitrogen cycle in a prairie stream0 aQuantification of the nitrogen cycle in a prairie stream a574 -5890 v33 aNitrogen (N) was added for 35 days in the form of 15NH4Cl to Kings Creek on Konza Prairie, Kansas. Standing stocks of N in key compartments (that is, nutrients, detritus, organisms) were quantified, and the amount of labeled N entering the compartments was analyzed. These data were used to calculate turnover and flux rates of N cycling through the food web, as well as nutrient transformation rates. Inorganic N pools turned over much more rapidly in the water column of this stream than in pelagic systems where comparable measurements have been made. As with other systems, the mass of ammonium was low but it was the key compartment mediating nutrient flux through the ecosystem, whereas dissolved organic N, the primary component of N flux through the system, is not actively cycled. Nitrification was also a significant flux of N in the stream, with rates in the water column and surface of benthos accounting for approximately 10% of the total ammonium uptake. Primary consumers assimilated 67% of the inorganic N that entered benthic algae and microbes. Predators acquired 23% of the N that consumers obtained. Invertebrate collectors, omnivorous crayfish (Orconectes spp.), and invertebrate shredders dominated the N flux associated with primary consumers. Mass balance calculations indicated that at least 23% of the 309 mg of 15N added during the 35 days of release was retained within the 210-m stream reach during the release. Overall, the rates of turnover of N in organisms and organic substrata were significantly greater when C:N was low. This ratio may be a surrogate for biological activity with regard to N flux in streams.10aaquatic insects10aC:N ratio10anitrogen cycle10anitrogen export10astream10aTrophic structure1 aDodds, W., K.1 aEvans-White, M.A.1 aGerlanc, N.M.1 aGray, L.1 aGudder, D.A.1 aKemp, M.J.1 aLo'pez, A.L.1 aStagliano, D.1 aStrauss, E.1 aTank, J.L.1 aWhiles, M.R.1 aWollheim, W. uhttp://129.130.186.12/content/quantification-nitrogen-cycle-prairie-stream01642nas a2200157 4500008004100000245010000041210006900141300001300210490000800223520107000231653002201301100001601323700001801339700001601357856011101373 1999 eng d00aThe effects of bison crossings on the macroinvertebrate community in a tallgrass prairie stream0 aeffects of bison crossings on the macroinvertebrate community in a253 -2650 v1413 aThe distribution and diversity of macroinvertebrates in relation to bison crossings was studied for four seasons in a headwater reach of a tallgrass prairie stream. Species richness was significantly higher above crossings only during the fall. Summer samples revealed significantly higher EPT (richness within only Ephemeroptera, Plecoptera and Trichoptera) index values above crossings than at crossings. On average, over 10% more fine sediment (<0.2 mm) occurred at the crossings than above or below crossings. Densities of two taxa (Hydropsyche spp. and Elmidae) were significantly higher above or below crossings, whereas three taxa (Bezzia/Palpomyia spp., Culicoides sp., and Naididae/Tubificidae) were significantly higher at crossings for at least one season. Overall, this study suggests that impact of bison on benthic communities of headwater streams was spatially limited. Although bison may have less impact upon stream communities than previous studies of cattle impacts have shown, differences in climate and stocking rate could be important factors.10atallgrass prairie1 aFritz, K.M.1 aDodds, W., K.1 aPontius, J. uhttp://129.130.186.12/content/effects-bison-crossings-macroinvertebrate-community-tallgrass-prairie-stream01817nas a2200229 4500008004100000245010800041210006900149300001300218490000700231520103400238653001901272653002301291653001901314653001701333653002301350653002501373100001601398700001601414700001801430700001701448856012201465 1999 eng d00aVariations in microbial activity due to fluctuations in soil water content at the water table interface0 aVariations in microbial activity due to fluctuations in soil wat a479 -5050 v343 aA soil column experiment was designed to investigate the response of an indigenous microbial population to a vertically fluctuating water table. A subsurface environment with a transitional zone was simulated. The water table in the soil columns was raised and lowered, and compared to columns under static conditions. Carbon dioxide and oxygen concentrations were measured. Peaks of CO2 occurred in the fluctuating columns immediately following a rise in the water table. Dissolved O2 in the fluctuating columns was consistently lower throughout the experiment, but these lower concentrations were exaggerated immediately following a rise in the water table. Values for total organic carbon in the pore water were slightly lower in the fluctuating columns. The results of this soil column study indicate that vertical fluctuation of the water table can enhance microbial activity of indigenous soil microbial populations. This increase in microbial activity suggests an increased rate of available carbon under these conditions.10abioremediation10amicrobial activity10asoil interface10asoil texture10aSoil water content10asubsurface sediments1 aBanks, M.K.1 aClennan, C.1 aDodds, W., K.1 aRice, C., W. uhttp://129.130.186.12/content/variations-microbial-activity-due-fluctuations-soil-water-content-water-table-interface00616nas a2200205 4500008004100000245003600041210003600077260003800113300001300151653002200164100001500186700002300201700002000224700001800244700002000262700001900282700001900301700002400320856006600344 1998 eng d00aHydrology and aquatic chemistry0 aHydrology and aquatic chemistry aNew YorkbOxford University Press a159 -17610atallgrass prairie1 aGray, L.J.1 aMacpherson, G., L.1 aKoelliker, J.K.1 aDodds, W., K.1 aKnapp, Alan, K.1 aBriggs, J., M.1 aHartnett, D.C.1 aCollins, Scott., L. uhttp://129.130.186.12/content/hydrology-and-aquatic-chemistry02256nas a2200133 4500008004100000245007100041210006900112300001100181490000700192520180200199100001802001700001402019856008902033 1998 eng d00aA portable chamber for in situ determination of benthic metabolism0 aportable chamber for in situ determination of benthic metabolism a49 -590 v393 a1. Many stream ecologists are interested in determining the metabolic rates of benthic organisms, particularly those of production and respiration. It is often necessary to make these measurements on fresh material in the field at remote sites. Recirculating chambers are commonly used for this purpose. 2. A broad variety of recirculating chambers are described in the literature, but each design has inherent limitations. The most common are inability to control flow in the chamber and match it with external flow rates, and a lack of the power required to do this for extended periods. Alteration of spectral irradiance, temperature rise and elevated internal chamber pressures are additional limitations that have received little attention. 3. We have designed and constructed a flow chamber that eliminates some of these problems. The chamber utilizes a DC motor-driven propeller as an efficient recirculator (axial impeller), minimizing power requirements and it is constructed of UVB transparent acrylic to allow a full spectral complement of solar irradiance in the interior. Modular components allow the chamber to be taken apart quickly for cleaning and replacement of parts, making it more functional than some previous designs. 4. The axial impeller chamber was compared to a similar sized conventional chamber that had a small diameter return line and a high capacity centrifugal pump. The axial impeller chamber had less of a temperature rise during field incubations, lower power consumption and less internal pressure in the return line when producing equivalent water velocities. 5. The reported axial impeller design had relatively homogeneous velocity across the working section relative to other chambers and was capable of water velocities in excess of 1 m s–1.1 aDodds, W., K.1 aBrock, J. uhttp://129.130.186.12/content/portable-chamber-situ-determination-benthic-metabolism00588nas a2200181 4500008004100000245005000041210005000091260003800141300001300179653002200192100001500214700001800229700002000247700001900267700001900286700002400305856007700329 1998 eng d00aStructure and dynamics of aquatic communities0 aStructure and dynamics of aquatic communities aNew YorkbOxford University Press a177 -18910atallgrass prairie1 aGray, L.J.1 aDodds, W., K.1 aKnapp, Alan, K.1 aBriggs, J., M.1 aHartnett, D.C.1 aCollins, Scott., L. uhttp://129.130.186.12/content/structure-and-dynamics-aquatic-communities02443nas a2200265 4500008004100000245014100041210006900182300001500251490000700266520159400273653001601867653001401883653001601897653001301913653001401926653001701940653001501957653001501972653001101987653001201998100001802010700001602028700001602044856011702060 1998 eng d00aSuggested classification for stream trophic state: Distributions of temperate stream types by chlorophyll, total nitrogen and phosphorus0 aSuggested classification for stream trophic state Distributions  a1455 -14620 v323 aAquatic scientists and managers have no conventional mechanism with which to characterize and compare nutrients and algal biomass in streams within a broader context analogous to trophic state categorization in lakes by chlorophyll (chl) and nutrients. We analyzed published data for a large number of distinct, temperate, stream sites for mean benthic chl (n=286), maximum benthic chl (n=176), sestonic chl (n=292), total nitrogen (n=1070), and total phosphorus (n=1366) as a first effort to establish criteria for trophic boundaries. Two classification systems are proposed. In the first system, the boundary between oligotrophic and mesotrophic categories is defined by the lower third of the cumulative distribution of the values. The mesotrophic–eutrophic boundary is defined by the upper third of the distribution. In the second system, individual streams are placed more precisely in a broad geographic context by assessing the proportion of streams that have greater or lesser nutrient and chl values. The proposed relationships for streams were compared to trophic criteria published for lakes. The proposed trophic boundaries for streams generally include a broader range of values in the mesotrophic range than conventional criteria for lakes. The ratio of maximum to mean benthic chl for streams was significantly higher than that found for planktonic chl in lakes, reflecting the greater variance in streams. This high variance in streams suggests that the proposed stream trophic criteria should be viewed only as a general first approach to categorizing stream ecosystems.10aChlorophyll10aeutrophic10amesotrophic10anitrogen10anutrients10aoligotrophic10aperiphyton10aPhosphorus10arivers10astreams1 aDodds, W., K.1 aJones, J.R.1 aWelch, E.B. uhttp://129.130.186.12/content/suggested-classification-stream-trophic-state-distributions-temperate-stream-types02598nas a2200181 4500008004100000245011900041210006900160300001300229490000700242520195000249653001102199653001102210653001202221653002402233653001502257100001802272856012602290 1997 eng d00aDistribution of runoff and rivers related to vegetative characteristics, latitude, and slope: A global perspective0 aDistribution of runoff and rivers related to vegetative characte a162 -1680 v163 aThe geographic distribution of streams on earth can be associated with terrestrial vegetation, slope, and latitude, among other factors. Classifying flowing water habitats by associated vegetative cover is useful because factors such as downstream transport of organic carbon (C), sediments, nutrients, and other dissolved or suspended materials are influenced heavily by the vegetative characteristics of the watershed. Global datasets with 1-degree spatial resolution were analyzed to characterize both volume of runoff and number of mapped rivers associated with each of 14 classes of vegetation, and how runoff is influenced by latitude and slope. The vegetation classes (land cover) were ranked in decreasing order with respect to runoff. About 30% of the global runoff originates from broadleaf evergreen forest, followed by wooded C4 grassland (14.8%), cultivated land (8.9%), coniferous forest and woodland (8.3%), ice (7.8%), wooded C3 grassland (6.0%), mixed coniferous and broadleaf deciduous forest (5.4%), C3 grassland (5.3%), tundra (4.5%), high latitude deciduous forest and woodland (3.9%), broadleaf deciduous forest and woodland (2.3%), C4 grassland (1.7%), shrubs and bare ground (1.4%), and desert and bare ground (0.5%). Numbers of mapped rivers followed a similar pattern, except that broadleaf evergreen forests did not dominate, and tundra habitats were much more important. Counts of intermittent rivers were generally highest in the areas with the lowest runoff. River counts are likely to be less reliable than runoff estimates because they rely upon the subjective judgment of cartographers. Equatorial and northern temperate regions accounted for the greatest proportion of total runoff. A weak positive relationship occurred between slope and runoff. This analysis may assist investigators in determining how well their results can be extrapolated beyond regional scales.10arivers10aRunoff10astreams10aTerrestrial systems10avegetation1 aDodds, W., K. uhttp://129.130.186.12/content/distribution-runoff-and-rivers-related-vegetative-characteristics-latitude-and-slope-global02353nas a2200133 4500008004100000245009900041210006900140300001300209490000700222520183400229100001802063700001802081856012002099 1997 eng d00aInfluence of protozoa and nutrient availability on nitrification rates in subsurface sediments0 aInfluence of protozoa and nutrient availability on nitrification a155 -1650 v343 aProtozoan abundance, nitrification potential, and related factors in saturated subsurface sediments and the overlying soil were compared at a nonfertilized grassland and an agricultural cropland site. In a 6-week laboratory experiment, DOC, ammonium, and protozoan abundance were manipulated in flasks containing groundwater-sediment slurries. Microbial abundance (protozoa, actively respiring bacteria, and total bacteria) and nutrient concentrations (extractable ammonium and nitrate) were measured. Results from the soil profile analysis showed that protozoan abundance declined with depth at both sites, but significant numbers (392 cells g−1dw) were found in groundwater sediments at the cropland site. Nitrification potential declined with depth at the grassland site and increased with depth at the cropland site. In the laboratory experiment, treatment responses generally were observed within 3 weeks, but had diminished by 6 weeks. Protozoa reduced bacterial populations through the first 3 weeks, but this effect was not significant by week 6. In the cropland sediments, increased net nitrate production occurred in the two reduced protozoa treatments that received ammonium, suggesting that nitrification was occurring and was limited by ammonium. High protozoan abundance in the cropland sediments increased the nitrate flux response, unless DOC was added; in this case, no response occurred. No such responses were recorded in the grassland sediments. Apparently, appreciable nitrification can occur in some groundwater sediments, if sufficient ammonium is present and DOC availability is low. Furthermore, nitrification can be enhanced when protozoan abundance is elevated. Finally, our results suggest that surface land use practices can alter subsurface nitrification rates and microbial community structure.1 aStrauss, E.A.1 aDodds, W., K. uhttp://129.130.186.12/content/influence-protozoa-and-nutrient-availability-nitrification-rates-subsurface-sediments02121nas a2200121 4500008004100000245009100041210006900132300001300201490000700214520164700221100001801868856011301886 1997 eng d00aInterspecific interactions: constructing a general, neutral model for interaction type0 aInterspecific interactions constructing a general neutral model  a377 -3830 v783 aExperiments have not been devised to provide unbiased estimates of the relative co-occurrence of all different interaction types in communities. Thus, we have no idea what types of interspecific interactions to expect if we randomly sample species from an environment. The probability that a unidirectional, non-zero interaction is negative (P-) or positive (P+) has a direct effect on the expected types of reciprocal interspecific interactions. Analysis of field studies where strengths and signs of interactions between seven or more species were documented (large studies were selected to avoid bias from choosing species known to interact) suggests that P+=P-=0.5. Data also suggest that the proportion of non-zero interactions (C) is generally less than 0.6 when 10 or more interactions are considered. The proportion of expected reciprocal interspecific interactions can be calculated given the proportion of direct interactions that are not significantly different from zero and assuming that non-zero interactions are equally likely to be positive or negative. In general, this neutral model predicts that if species are chosen from an environment randomly, non-interaction (0/0), commensalism (+/0), or amensalism (-/0) will be most common when C < 0.6. Predation and functionally similar interactions (+/-), competition (-/-), and mutualism (+/+) should be relatively rare when there are less than 10 species with C < 0.6. Predation should be twice as common as competition or mutualism, and mutualism as common as competition. The neutral model suggests that community ecologists place undue emphasis on competition and predation.1 aDodds, W., K. uhttp://129.130.186.12/content/interspecific-interactions-constructing-general-neutral-model-interaction-type02294nas a2200193 4500008004100000245009600041210006900137300001300206490000700219520163600226100001801862700001601880700001701896700001701913700001801930700001801948700001101966856012301977 1996 eng d00aBiological properties of soil and subsurface sediments under abandoned pasture and cropland0 aBiological properties of soil and subsurface sediments under aba a837 -8460 v283 aLittle is known about the effects of most surface land-use practices on shallow subsurface microbial communities. We analyzed duplicate cores taken aseptically from up to 10 m depth from unconsolidated valley sediments (soils) beneath an abandoned pasture reverting to tall grass prairie and cropland. Both profiles had similar soil texture, with moderately higher silt under cropland and a slight decrease in clay with depth. Soluble organic C was about two times higher in the grassland site and dissolved O2 was about 8% lower compared with the cropland site. Water content and C-to-N ratios were greatest at the grassland surface but were less in the grassland than the cropland site within 2 m depth. In general, numbers of aerobic heterotrophic bacteria and protozoa decreased with depth until the saturated zone (4.3 m in grassland and 5.3 m in the cropland site). Bacterial numbers as determined by plate counts were about 10-fold less at the groundwater interface than in the surface soils at both sites. Direct microscopic counts of total bacteria were approximately the same in the surface soil and the sediments at the top of the water table at both sites. The top of the water table generally did not exhibit elevated microbial biomass or activity relative to deeper sediments. There was no significant relationship between protozoan numbers and microbial thymidine uptake at the cropland site, but a negative relationship was observed at the grassland site. The data suggest that cultivation may affect microbial biomass and activity in the subsurface, as well as community interactions between protozoa and bacteria.1 aDodds, W., K.1 aBanks, M.K.1 aClenan, C.S.1 aRice, C., W.1 aSotomayor, D.1 aStrauss, E.A.1 aYu, W. uhttp://129.130.186.12/content/biological-properties-soil-and-subsurface-sediments-under-abandoned-pasture-and-cropland01739nas a2200133 4500008004100000245006400041210005900105300001300164490000700177520130500184100001401489700001801503856008401521 1996 eng d00aThe ecology of a subterranean isopod, Caecidotea tridentata0 aecology of a subterranean isopod Caecidotea tridentata a249 -2590 v353 a1. The blind isopod Caecidotea tridentata is the dominant invertebrate in a simple community of subterranean organisms inhabiting the local, shallow aquifer under Konza Prairie, Kansas, U.S.A. 2. The ecology of this karst aquifer was explored by sieving water from a spring, collecting water samples for analysis, and manipulating sediments and invertebrates in the laboratory. The size frequency distribution was stable and gravid females were present throughout the year, suggesting continuous reproduction. 3. The number of isopods collected per litre was negatively correlated with discharge and the abundance of bacteria, but positively related to the numbers of an amphipod (Bactrurus hubrichti). This may be explained if both the isopods and the amphipods track the saturated zone below the top of the water table; at lower discharge, the top of the water table is closer to the spring outlet. The suspended bacteria wash out in greater numbers with high discharge. 4. When isopods and carbon were added in a pairwise experimental design to sediments collected from the aquifer, the isopods significantly stimulated numbers and activity of planktonic and sedimentary bacteria, while carbon had no effect. This suggests that invertebrates can affect the microbes locally in an aquifer.1 aEdler, C.1 aDodds, W., K. uhttp://129.130.186.12/content/ecology-subterranean-isopod-caecidotea-tridentata01626nas a2200181 4500008004100000245006000041210005600101300001100157490000700168520107900175653002101254653001601275653002301291653001401314100001801328700001801346856008001364 1996 eng d00aThe effect of density dependence on community structure0 aeffect of density dependence on community structure a33 -420 v933 aThe effect of population density controls on the relationship between stability and species richness was explored by constructing Monte Carlo community models with density dependent population controls. Simulated communities with more initial species exhibit proportionally fewer extinctions. This form of stability is greatest at low interaction strengths and intermediate connectivities. Stability appeared to be related to the fact that species with more interactions were less likely to be driven to extinction by negative interactions. Species with mutualistic (+ / +) and commensal (0/ +) interactions survive at greater than expected proportions, while those with relatively more competitive (− / −) and amensal (0 / −) interactions tend toward extinction. Incorporation of density dependent population control thus leads to features that previous community models have not exhibited. It is suggested that communities with many of the populations controlled by abiotic factors in a density dependent fashion should exhibit increased stability with more species.10aCommunity matrix10aCompetition10adensity dependence10amutualism1 aDodds, W., K.1 aHenebry, G.M. uhttp://129.130.186.12/content/effect-density-dependence-community-structure01546nas a2200145 4500008004100000245012200041210006900163300001300232490000700245520097800252100001801230700001501248700001401263856012301277 1996 eng d00aMicrocosms for aquifer research: Application to colonization of various sized particles by groundwater microorganisms0 aMicrocosms for aquifer research Application to colonization of v a756 -7590 v343 aFlow-through microcosms were constructed to conduct ecological experiments on aquifer organisms. The two 5-channel microcosms were simple to construct, were fed by an artesian spring, and maintained close to in situ temperature and O2 concentrations. They were used to test relative microbial colonization of three substrate sizes: silt (0.063 mm), sand (0.9 mm), and gravel (3 mm). After 96 days of incubation, O2 microelectrode measurements revealed the lowest O2 tension in the silt, the highest in the gravel, and intermediate values in the sand. Microbial activity (3[H]-thymidine incorporation) was greatest in the gravel, followed by sand and then silt. Denitrification was greatest in the silt, followed by sand and then gravel. Microbial activity may be greatest with the largest particle size because of increased water exchange through pores, and denitrification may be greatest with the smallest particle sizes because of the occurrence of anaerobic microzones.1 aDodds, W., K.1 aRandel, C.1 aEdler, C. uhttp://129.130.186.12/content/microcosms-aquifer-research-application-colonization-various-sized-particles-groundwater02128nas a2200193 4500008004100000245005700041210005700098300001300155490000700168520154600175653002201721100001801743700002001761700001801781700002001799700001801819700001501837856008201852 1996 eng d00aNitrogen transport from tallgrass prairie watersheds0 aNitrogen transport from tallgrass prairie watersheds a973 -9810 v253 aDischarge and N content of surface water flowing from four Karst watersheds on Konza Prairie Research Natural Area, Kansas, managed with different burn frequencies, were monitored from 1986 to 1992. The goal was to establish the influence of natural processes (climate, fire, and bison grazing) on N transport and concentration in streams. Streams were characterized by variable flow, under conditions that included an extreme flood and a drought during which all channels were dry for over a year. The estimated groundwater/stream water discharge ratio varied between 0.15 to 6.41. Annual N transport by streams, averaged across all watersheds and years, was 0.16 kg N ha−1 yr−1. Annual N transport per unit area also increased as the watershed area increased and as precipitation increased. Total annual transport of N from the prairie via streams ranged from 0.01 to 6.0% of the N input from precipitation. Nitrate and total N concentrations in surface water decreased (P < 0.001, r values ranged from 0.14–0.26) as length of time since last fire increased. Increased watershed area was correlated negatively (P < 0.0001) to stream water concentrations of NO−3N and total N (r values = −0.43 and −0.20, respectively). Low N concentration is typical of these streams, with NH+4-N concentrations below 1.0 µg L−1, NO−3-N ranging from below 1.4 to 392 µg L−1, and total N from 3.0 to 714 µg L−1. These data provide an important baseline for evaluating N transport and stream water quality from unfertilized grasslands.10atallgrass prairie1 aDodds, W., K.1 aBlair, John, M.1 aHenebry, G.M.1 aKoelliker, J.K.1 aRamundo, R.A.1 aTate, C.M. uhttp://129.130.186.12/content/nitrogen-transport-tallgrass-prairie-watersheds02484nas a2200265 4500008004100000245011800041210006900159300001300228490000800241520163600249653001801885653001001903653001001913653001501923653002301938653001901961100001801980700001701998700001702015700001602032700001702048700001602065700001302081856012402094 1996 eng d00aThe relationship of floods, drying, flow and light to primary production and producer biomass in a prairie stream0 arelationship of floods drying flow and light to primary producti a151 -1590 v3333 aFactors related to autochthonous production were investigated at several sites along a prairie stream at Konza Prairie Research Natural Area. Primary production, algal biomass, litter input, and ability of floods to move native substrate were measured. Additional experiments were conducted to establish the influence of light and water velocity on primary production rates and recovery of biomass following dry periods. The study period encompassed two extreme (> 50 year calculated return time) floods, thus we were able to analyze the effects of scour on periphyton biomass and productivity. Biomass of sedimentary algae was reduced greatly by flooding and did not reach preflood amounts during the 2 months following the first flood. Rates of primary production associated with sediments recovered to levels above preflood rates within 2 weeks. Biomass of epilithic periphyton was not affected as severely as that of sedimentary algae. Little relationship was observed between water velocity and photosythetic rates. Production reached maximum rates at 25% of full sun light. Epilithic chlorophyll levels recovered within eight days following a dry period, and chl a was an order of magnitude greater on rocks than sediments 51 days after re-wetting. Estimated annual rates of primary production were 2.6 times greater in the prairie than in the forest reaches of the stream. The ratio of annual autochthonous:allochthonous carbon input was 4.81 for prairie and 0.32 for the forest. Periphyton production in prairie streams is resilient with regard to flooding and drought and represents a primary carbon source for the system.10aautochthonous10aFlood10alight10aperiphyton10aPrimary production10awater velocity1 aDodds, W., K.1 aHutson, R.E.1 aEichem, A.C.1 aEvans, M.E.1 aGudder, D.A.1 aFritz, K.M.1 aGray, L. uhttp://129.130.186.12/content/relationship-floods-drying-flow-and-light-primary-production-and-producer-biomass-prairie01492nas a2200169 4500008004100000245014300041210006900184300001500253490000700268520092100275100001101196700001801207700001601225700001601241700001801257856004701275 1995 eng d00aOptimal staining and sample storage time for direct microscopic enumeration of total and active bacteria in soil with two fluorescent dyes0 aOptimal staining and sample storage time for direct microscopic  a3367 -33720 v613 aDirect counting techniques, first developed for aquatic samples, can be used to enumerate bacteria in soil and groundwater sediments. Two fluorescent dyes, 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) for actively respiring bacteria and 4(prm1),6-diamidino-2-phenylindole (DAPI) for total bacteria, were tested for their usefulness in epifluorescent direct bacterial enumeration in soil. Both dyes can be used for the same soil sample without affecting enumeration results. Staining for 8 h with CTC and for 40 min with DAPI resulted in maximum numbers of stained cells. The optimal DAPI staining concentration is 10 mg liter(sup-1). After preparation, slides should be stored at 4(deg)C and counted within 2 days for CTC and within 24 h for DAPI. Sodium PP(infi) or sodium chloride solutions were used to desorb bacteria from soil prior to counting. Counts were significantly higher when sodium chloride was used.1 aYu, W.1 aDodds, W., K.1 aBanks, M.K.1 aSkalsky, J.1 aStrauss, E.A. uhttp://aem.asm.org/content/61/9/3367.short02084nas a2200193 4500008004100000245010300041210006900144300001100213490000700224520141600231653001601647653001801663653001401681653001301695653002501708100001801733700001801751856012101769 1995 eng d00aSimulation of responses of community structure to species interactions driven by phenotypic change0 aSimulation of responses of community structure to species intera a85 -940 v793 aWe developed a community model which considers the effect of phenotype on species interaction in order to elucidate general relationships between phenotype, species interactions and community structure. The model consists of community matrices with density-dependent species interactions and a limit on the total population of each species. A general natural pattern forms the basis of the model: organisms which are most similar compete, those which are less similar may enter into a predator-prey relationship, and those which are most different may be mutualistic. In this model, contrary to some previously published studies, increasing the number of species increased stability of community matrices. The rate of change in phenotype was varied to assess the response of community characteristics. At the highest rate of random phenotypic change there were the most species; the minimum number of species was found at intermediate rates of change. The models were run in the absence of predation, competition, or mutualism. The absence of mutualism led to more extinction. The absence of competition caused communities to quickly reach a population ceiling. Results suggest that it is extremely important to understand the relative occurrence of mutualism and competition in natural communities. Furthermore, the rate of phenotypic change could be an important but subtle determinant of community structure.10aCompetition10ainterspecific10amutualism10anetworks10aSpecies interactions1 aDodds, W., K.1 aHenebry, G.M. uhttp://129.130.186.12/content/simulation-responses-community-structure-species-interactions-driven-phenotypic-change01982nas a2200157 4500008004100000245006900041210006900110300001500179490000700194520151300201100001501714700001801729700001501747700001401762856004801776 1993 eng d00aMicrobial decomposition of elm and oak leaves in a karst aquifer0 aMicrobial decomposition of elm and oak leaves in a karst aquifer a3592 -35960 v593 aDry Chinquapin oak (Quercus macrocarpa) and American elm (Ulmus americana) leaves were placed in four microcosms fed by groundwater springs to monitor changes in dry mass, ash-free dry mass, and microbial activity over a 35-day period. Oxygen microelectrodes were used to measure microbial activity and to estimate millimeter-scale heterogeneity in that activity. Oak leaves lost mass more slowly than elm leaves. Generally, there was a decrease in total dry weight over the first 14 days, after which total dry weight began to increase. However, there were consistent decreases in ash-free dry mass over the entire incubation period, suggesting that the material remaining after initial leaf decomposition trapped inorganic particles. Microbial activity was higher on elm leaves than on oak leaves, with peak activity occurring at 6 and 27 days, respectively. The level of oxygen saturation on the bottom surface of an elm leaf ranged between 0 and 75% within a 30-mm2 area. This spatial heterogeneity in O2 saturation disappeared when the water velocity increased from 0 to 6 cm s-1. Our results suggest that as leaves enter the groundwater, they decompose and provide substrate for microorganisms. The rate of decomposition depends on leaf type, small-scale variations in microbial activity, water velocity, and the length of submersion time. During the initial stages of decomposition, anoxic microzones are formed that could potentially be important to the biogeochemistry of the otherwise oxic aquifer.1 aEichem, A.1 aDodds, W., K.1 aTate, C.M.1 aEdler, C. uhttp://aem.asm.org/content/59/11/3592.short00573nam a2200193 4500008004100000245004000041210004000081260005400121300001000175100001600185700001600201700001700217700001800234700002000252700001500272700001500287700001400302856006300316 1993 eng d00aStream Research in the LTER Network0 aStream Research in the LTER Network aSeattle, WAbLTER Network LTER publication no. 15 a114 -1 aMeyer, J.L.1 aCrocker, T.1 aD'Angelo, D.1 aDodds, W., K.1 aFindlay, S.E.G.1 aOswood, M.1 aRepert, D.1 aToetz, D. uhttp://129.130.186.12/content/stream-research-lter-network00463nas a2200109 4500008004100000245009000041210006900131300001100200100001400211700001800225856011000243 1992 eng d00aCharacterization of a groundwater community dominated by Asellus tridentata (Isopoda)0 aCharacterization of a groundwater community dominated by Asellus a91 -991 aEdler, C.1 aDodds, W., K. uhttp://129.130.186.12/content/characterization-groundwater-community-dominated-asellus-tridentata-isopoda