Sediment microbial community structure and mercury methylation in mercury-polluted Clear Lake, California

Spatial and temporal variations in sediment microbial community structure i n a eutrophic lake polluted with inorganic mercury were identified using po lar lipid fatty acid (PLFA) analysis, Microbial community structure was str ongly related to mercury methylation potential , sediment organic carbon co ntent, and lake location. Pore a ater sulfate, total mercury concentrations , and organic matter C/N ratios showed no relation ships with microbial com munity structure. Seasonal changes and changes potentially attributable to temperature regulation of bacterial membranes were detectable but were less important influences on sediment PLFA composition than were differences du e to lake sampling location. Analysis of biomarker PLFAs characteristic of Desulfobacter and Desulfovibrio groups of sulfate-reducing bacteria suggest s that Desulfobacter-like organisms are important mercury methylators in th e sediments, especially in the Lower Arm of Clear Lake.