THE EFFECTS OF DROUGHT AND STREAM DRYING ON AQUATIC INVERTEBRATES AT POINT REYES NATIONAL SEASHORE
Anthony Sanabria, Michael Bogan, Stephanie M. Carlson.
University of California, Berkeley, Berkeley, CA.
Drought affects streams by decreasing water flow and surface area. As a result, some streams become dry over the summer season (intermittent streams), while others remain wetted throughout the entire year (perennial streams). For the last 4 years, California has been in a record-breaking drought. Because of this record-breaking drought, more and more perennial streams may be turning into intermittent streams. Our objective is to understand how stream drying influences the density and species richness of aquatic invertebrates in the Pine Gulch Watershed at Point Reyes National Seashore in Northern California. From February to March 2015, we collected invertebrate samples from 5 perennial sites and 5 intermittent sites along Pine Gulch and its tributaries. To calculate species richness and density, we counted and sorted the invertebrates down to the species level. Moreover, flow sensors monitored the water flow duration at the time when samples were taken at each site. We found a total of 139 species, with individual sites varying from 25 species at an intermittent site to 67 species at a perennial site. Our data showed higher density and species richness in the perennial sites than the intermittent sites, and that longer flow duration in the intermittent sites was correlated with increased density and species richness. Based on our findings, if California’s record-breaking drought continues in the coming years, we would expect to see a much greater loss of biodiversity in both present-day intermittent streams and streams that transition from perennial to intermittent.