Sediment Microbial Community Structure and Mercury Methylation in Mercury-Polluted Clear Lake, California

Spatial and temporal variations in sediment microbial community structure in a eutrophic lake polluted with inorganic mercury were identified using polar lipid fatty acid (PLFA) analysis. Microbial community structure was strongly related to mercury methylation potential, sediment organic carbon content, and lake location. Pore water sulfate, total mercury concentrations, and organic matter C/N ratios showed no relationships with microbial community 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 due to lake sampling location. Analysis of biomarker PLFAs characteristic of Desulfobacter and Desulfovibrio groups of sulfate-reducing bacteria suggests that Desulfobacter-like organisms are important mercury methylators in the sediments, especially in the Lower Arm of Clear Lake.

本研究采用极性脂脂肪酸（polar lipid fatty acid，PLFA）分析方法，解析了受无机汞污染的富营养化湖泊沉积物微生物群落结构的时空变异规律。沉积物微生物群落结构与汞甲基化潜能、沉积物有机碳含量及湖泊采样点位存在显著相关性。孔隙水硫酸盐浓度、总汞浓度及有机质碳氮比与微生物群落结构无显著关联。虽可观测到季节变化及可能由细菌细胞膜温度调控引发的群落结构变化，但相较于湖泊采样点位差异，其对沉积物PLFA组成的影响程度更低。针对硫酸盐还原菌中脱硫杆菌属（Desulfobacter）与脱硫弧菌属（Desulfovibrio）的特征生物标记PLFA的分析结果表明，类脱硫杆菌属微生物是沉积物中重要的汞甲基化类群，在克莱尔湖（Clear Lake）下湾区域尤为显著。