REU: Debris Dams as Mitigating Patches for Stream Fauna During Floods

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Communities which persist in the face of severe disturbances may do so because the impact of the disturbance is mitigated by patch configuration coupled with dispersal. This proposal examines this issue for lotic invertebrates which are known to rapidly recover from floods but for which the recovery mechanisms are not known. The PI will test the general hypothesis that mitigating patches, namely debris dams, lessen the detrimental effect of floods on stream meiofauna by reducing faunal displacement during floods and by facilitating return of displaced fauna to the stream bottom following flood. Experimental tests of specific hypotheses are outlined to address both the magnitude of the effect that these mitigating patches have on the fauna and the mechanisms underlying the effects. Experiments will involve: (1) field quantification of how the spatial patterns of the fauna are effected by the proposed mitigating patches and by flood; (2) field experiments in which patches are manipulated and recovery of fauna compared with unmanipulated sites; and (3) field and flume studies examining the mechanisms responsible for faunal response to mitigating patches. The results will provide information on how natural disturbances effect equilibrium conditions.