ASSESSING IMPACTS OF ANTHROPOGENIC CONTAMINANTS ON MICROBIAL COMMUNITIES AND ORGANIC MATTER COMPOSITION IN TWO WEST COAST ESTUARIES USING ORGANIC GEOCHEMICAL TECHNIQUES
We compare a core from South San Francisco Bay [1.2 m, 2-cm to 5-cm intervals, ≤ 50 y age range], a highly urbanized estuary that receives urban and agricultural runoff and wastewater discharge, and a core from Elkhorn Slough (CA) [0.76 m, 1-cm to 5-cm intervals, ~300 y age range], a more pristine estuary that receives mainly agricultural input. We measured downcore profiles of total organic carbon (TOC), nitrogen (N), δ13C and δ15N of bulk organic matter and several classes of current use, legacy, and emerging contaminants [e.g., carbamates, anilines, triazines, organophosphates, DDT/DDD/DDE, chloracetanilides, pyrethroids, PAHs]. We found notable differences between the two cores and in each core through time, attesting to the environmental and ecological changes that have taken place in recent decades to centuries [San Francisco Bay/Elkhorn Slough: TOC = 1 3/2 7%, N = 0.1 0.2/0.2 0.5%, δ13C = -24 -27/-24 -27, δ15N = 4 9/2 7].
In addition to these baseline data, we are beginning to assess the impact of anthropogenic contamination on microbial populations and other OM sources through the use of molecular tracers, (lipid biomarkers), e.g., organic compound classes such as aliphatic hydrocarbons, fatty acids and sterols. We are in the process of determining biomarker distributions in the two sediment cores, and relating these to the concentration profiles of organic contaminants to determine if changes in the microbial community composition can be linked to contamination and/or changes in OM sources.