00728nas a2200181 4500008004500000245012700045210006900172100001700241700001700258700002800275700001800303700002300321700002400344700001700368700001800385700002300403856012000426 In Press eng d 00aRemoving a perched culvert facilitates dispersal of fishes in an intermittent prairie stream but not recovery from drought0 aRemoving a perched culvert facilitates dispersal of fishes in an1 aGido, K., B.1 aHedden, S.C.1 aBruckerhoff, Lindsey, A1 aPennock, C.A.1 aHedden, Crosby, K.1 aHopper, Garrett, W.1 aRenner, E.A.1 aJohnson, E.R.1 aPostlethwait, B.J. uhttp://129.130.186.12/content/removing-perched-culvert-facilitates-dispersal-fishes-intermittent-prairie-stream-not03424nas a2200217 4500008004100000245011800041210006900159300001200228490000700240520268800247100002402935700001702959700002302976700002302999700002303022700002203045700002503067700002303092700002903115856006203144 2020 eng d00aBiomass loss and change in species dominance shift stream community excretion stoichiometry during severe drought0 aBiomass loss and change in species dominance shift stream commun a403-4160 v653 a

    1. Animals contribute significantly to nutrient cycling through excretion, but most studies consider their effects under relatively benign abiotic conditions. Disturbances such as drought may alter animals’ nutrient contributions through shifts in species composition and biomass. Headwater streams are particularly vulnerable to extreme climate events and thus might show rapid changes in stream biota and their ecosystem effects.
    2. We tested how biomass and subsequent ecosystem effects (nutrient cycling) of an intermittent prairie stream community changed during a drought. We quantified the biomass and contributions to nutrient cycling for assemblages comprising fishes, crayfish, and tadpoles in 12 isolated pools over 3 months encompassing the harshest drought on record for Kings Creek, KS, U.S.A. We predicted that macroconsumer biomass would decline with pool surface area and that differences in macroconsumer biomass and taxonomic composition would lead to different contributions of pool assemblages to nutrient cycling.
    3. The biomass of pool assemblages declined with decreasing pool size, a pattern apparently driven by mortality, emigration, or metamorphosis. We also observed a change in assemblage structure of drying pools during drought relative to pool size, shifting dominance toward species with more drought‐resistant traits. Accordingly, assemblage nitrogen (N) excretion rates declined as pool biomass was reduced, leading to a 58% reduction in N available to epilithic biofilms. Phosphorus (P) excretion rates declined from June to July, but increased in August, as species with high P excretion rates maintained similar proportional biomass and biomass of a non‐native fish increased. Molar N:P of pool assemblage excretion declined significantly throughout the drought and coincided with loss of southern redbelly dace (Chrosomus erythrogaster: Cyprinidae).
    4. Animal‐mediated nutrient cycling was altered by the loss of biomass and stoichiometric traits of taxa that differed in their occurrences and ability to tolerate abiotic conditions during drought. Elevated availability of dissolved N in isolated pools may increase N uptake rates by biofilms during drought conditions, indicating the importance of N excreted by aggregated macroconsumers, especially those with unique stoichiometric traits. While the significance of shifts in the composition of freshwater communities to ecosystems is not entirely known, additional losses in ecosystem function and changes in community structure may follow episodes of severe drought.
 

1 aHopper, Garrett, W.1 aGido, K., B.1 aPennock, Casey, A.1 aHedden, Skyler, C.1 aGuinnip, James, P.1 aFisher, Molly, A.1 aTobler, Courtney, M.1 aHedden, Crosby, K.1 aBruckerhoff, Lindsey, A. uhttps://onlinelibrary.wiley.com/doi/pdf/10.1111/fwb.1343302694nas a2200205 4500008004100000022001400041245011000055210006900165490000700234520201300241100002402254700001702278700002302295700002302318700002402341700001602365700002302381700002902404856005502433 2020 eng d a1015-162100aNowhere to swim: interspecific responses of prairie stream fishes in isolated pools during severe drought0 aNowhere to swim interspecific responses of prairie stream fishes0 v823 a

Extreme drying can dramatically shift abiotic characteristics of streams and species respond differently as conditions change. We modified a conceptual model describing responses of aquatic invertebrate assemblages to stream drying to facilitate predictions of fish assemblage shifts in which thresholds of physiochemical gradients lead to punctuated losses of fish diversity as stream connectivity diminishes. We tested the applicability of this model during a record-breaking drought that reduced a perennial reach of a headwater prairie stream to a series of 12 isolated pools with variable levels of hyporheic connectivity that was associated with pool volume. We tracked fish assemblage structure in pools over seven weeks and measured abiotic conditions. Inter-specific differences in drought resistance traits were tested in the lab (i.e., thermal and hypoxia tolerance) for common species experiencing drought conditions. Species richness declined rapidly with pool volume associated with hyporheic connectivity. Abundance of the most common species prior to drought, Chrosomus erythrogaster (southern redbelly dace) declined 95% and was extirpated from five pools during drought due to its low thermal tolerance. Despite being the least tolerant to hypoxia, Campostoma anomalum (central stoneroller) populations persisted in most pools. The remaining pools became dominated by a non-native extremophile fish, Gambusia affinis (western mosquitofish) and abundances of less resistant native species declined. Our study demonstrates that richness in drying pools is driven by factors associated with pool volume, and assemblage composition shifts from dominance by native species adapted to variable hydrological conditions to non-native species able to resist increasing temperatures and hypoxia. Sudden species loss associated with reduced stream connectivity can shift abundance patterns of prairie stream fish communities with potentially lagged effects on population and community dynamics.

1 aHopper, Garrett, W.1 aGido, K., B.1 aPennock, Casey, A.1 aHedden, Skyler, C.1 aFrenette, Bryan, D.1 aBarts, Nick1 aHedden, Crosby, K.1 aBruckerhoff, Lindsey, A. uhttp://link.springer.com/10.1007/s00027-020-0716-2