RELATIONSHIP BETWEEN MICROBIAL COMMUNITIES AND METAL MOBILITY IN URBAN WATERSHEDS, EASTERN SAN FRANCISCO BAY AREA, CA

Urban watershed-reservoir systems in the eastern San Francisco Bay area were investigated to determine the relationship between microbial communities and metal pollutant mobility. Results indicate that microbes and redox conditions play an important role in metal solubility. Three sites were selected for this research: 1) Lake Aliso/Lion Creek, a watershed impacted by an abandoned sulfur mine; 2) San Lorenzo Creek Reservoir/San Lorenzo Creek, located adjacent to a major freeway in an urban area; and 3) Lake Anza/Wildcat Creek, a low human impact watershed. Corresponding water and surface sediment samples were collected from each reservoir and from the primary tributaries that discharge into each of these reservoirs during summer 2013. DNA was extracted from each water and sediment sample then the 16S rRNA gene was amplified by polymerase chain reactions (PCR) and sequenced to determine the microbial community composition. Samples were also analyzed for metal concentration using inductively coupled plasma mass spectrometry (ICP-MS) and for field parameters including dissolved oxygen, pH, conductivity, and temperature using a YSI multiprobe. Total Iron (Fe) concentrations in Lake Aliso waters increase between the lake inlet and outlet. This increase suggests that Fe is mobilized within the lake and will be transported downstream through the lake outlet. Conversely, total Fe concentration in waters collected from San Lorenzo Creek Reservoir and Lake Anza decreased between the inlets and outlets. The downstream decrease in Fe in these two lakes suggests that the sediments retained Fe. All three reservoirs exhibit a decrease in Nickel (Ni) concentrations between the inlets and outlets, however, the patterns of other trace metals are less consistent. Results presented from this project will include how microbial populations are related to metal mobility. Conclusions from this study may be useful in the mitigation of redox sensitive pollutants in watersheds with small reservoirs.