Linking Shifts in Community and Trophic Structure to Altered Streamflow Regime

Recent studies discuss the coupling of lotic organisms to stream flow patterns and how human induced hydrographic alterations can disrupt these relationships. The objective of this study is to develop correlations between specific deviation in the natural streamflow patterns with shifts in trophic and community structure in low order alpine streams in eastern California. To isolate the impact of altered flow regime on periphyton and benthic macroinvertebrate communities, relatively undisturbed regulated and unregulated stream reach pairings were selected based on similar geographic and geomorphic characteristics. Although analyses of abiotic parameters show little difference between stream reach pairings, preliminary analyses of biological data show a reduction in the BMI community diversity (H), a decrease in the scraper abundance, and an increase in Chlorophyll A in regulated reaches. Initial investigations of stream hydrographs show an increase in summer and winter flows and a decrease in spring high flows in regulated streams. Future investigations will analyze fish communities, temperature variability, and water quality parameters with the goal of determining if specific shifts in community and trophic structure can be correlated to specific deviations in the natural hydrograph, and if so, which components contribute the most to structuring these communities.