SEASONAL CHANGES OF INVERTEBRATE COMMUNITY COMPOSITION IN INTERMITTENT STREAMS
Christopher Hernandez, Michael Bogan, Stephanie M. Carlson.
University of California, Berkeley, Berkeley, CA.
Flow regimes of intermittent streams, which cease flowing for several months each year, support a variety of invertebrates that play a vital role in the recruitment of native fish species. Seasonal flow variation supports different communities and densities of invertebrates. Fishes may benefit more from certain types of invertebrates. Our objective is to determine how invertebrate communities in an intermittent stream, Coyote Creek, California, change over the course of a year, as this rainfall-dominated stream’s flow magnitude changes over time. Perennial pools and seeps were sampled in late summer of 2014, and intermittent riffles in flowing reaches were sampled every 7 weeks following flow resumption in December 2014. To determine species composition and richness, we counted and sorted invertebrates down to the most practical taxonomic level, usually genus or species. Preliminary results show that perennial pools and seeps have the highest species richness as well as a unique community composition that differs significantly from intermittent reaches of the stream. Although our study is still in progress, strong trends are already visible. As flow duration increased over time, species composition in intermittent streams changed to more closely resemble perennial pools and seeps. Data can be used by water management organizations to make decisions on how to alter flow of intermittent streams in a way that minimizes impact to fish species of interest. Climate change may alter rainfall patterns in ways that increase the intensity of the dry season in intermittent streams, making it important to understand how ecological communities will be affected.