THE EFFECTS OF STREAM DRYING ON AQUATIC INVERTEBRATES IN THE CHALONE CREEK WATERSHED
Miranda Gonzales, Michael Bogan, Stephanie M. Carlson.
University of California, Berkeley, Berkeley, CA.
Drought intensity has increased in recent years, creating a need for studies on the effects these events have on ecosystems. With increased drought, streams are at risk of altered flow patterns, including complete stream drying and longer periods without flow. Our objective is to understand how drought and stream drying impact biodiversity in the Chalone Creek watershed, an intermittent stream network in northern California. Intermittent streams naturally dry for part of the year, but vary from having short (weeks) to extended (months) dry periods. We collected aquatic invertebrates from 10 reaches in the watershed to measure invertebrate density and species richness at each site. Flow sensors at each site measured how long each site had been flowing prior to sampling and the overall annual flow duration. In the lab, invertebrates were counted and classified as to species, and we compared density and species richness with flow duration. Annual flow duration for all sites ranged from 10% to 60%, and flow prior to sampling ranged from 15 to 106 days. We found 116 invertebrate species across all sites, with individual site richness ranging from 12 to 54 species. Higher annual flow resulted in higher species richness and lower density of invertebrates. Sites that had been flowing longer before sampling also exhibited higher species richness compared to sites that had flowed for less time. If extreme drought continues, intermittent streams will dry for longer periods, reducing biodiversity. Additionally, streams that currently flow year-round may become intermittent and lose biodiversity.