Measuring the Influence of Flow Regime on Biological Communities: Investigating Abiotic and Biotic Determinants of Algal, Macroinvertebrate, and Fish Assemblage Structure

Alterations to flow regime due to anthropogenic factors have been cited as one of the greatest emerging threats to stream biodiversity. To address the emerging issue of flow alteration recent studies have explored characterization of environmental flows (e-flows) which are distinguished by the quantity, timing, and quality of flows necessary to maintain ecological integrity. Effective implementation of environmental flows can only be achieved through an understanding of the influence of flow regime on biotic assemblages. However, it can be difficult to elucidate robust flow-ecology relationships because often the influence of flow regime can be convoluted or masked by co-varying abiotic and biotic factors. Using biotic data obtained from the Water Quality Portal and flow data collected by USGS gauging stations across the contiguous United States we investigated the relative influence of aspects of flow regime on algal, macroinvertebrate, and fish assemblage structure in respect to additional environmental factors. We examined assemblage metrics following an IT multiple regression approach with a priori selected predictor variables representing hydrology, land use, climate, and local physical habitat. Initial results will be presented and their contribution to existing flow-ecology literature will be discussed.