DISTRIBUTION OF TOTAL MERCURY AND METHYL MERCURY IN WATER, SEDIMENT, AND FISH FROM SOUTH FLORIDA ESTUARIES

Concentrations of total mercury and methyl mercury were determined in sediment and fish collected from estuarine waters of Florida to unders tand their distribution and partitioning. Total mercury concentrations in sediments ranged from 1 to 219 ng/g dry wt. Methyl mercury account ed for, on average, 0.77% of total mercury in sediment. Methyl mercury concentrations were not correlated with total mercury or organic carb on content in sediments. The concentrations of total mercury in fish m uscle were between 0.03 and 2.22 (mean: 0.31) mu g/g, wet wt, with met hyl mercury contributing 83% of total mercury. Methyl mercury concentr ations in fish muscle were directly proportional to total mercury conc entrations. The relationship of total and methyl mercury concentration s in fish to those of sediments from corresponding locations was fish- species dependent, in addition to several abiotic factors. Among fish species analyzed, hardhead catfish, gafftopsail catfish, and sand seat rout contained the highest concentrations of mercury. Filtered water s amples from canals and creeks that discharge into the Florida Bay show ed mercury concentrations of 3-7.4 ng/L, with methyl mercury accountin g for <0.03-52% of the total mercury. Consumption of fish containing 0 .31 mu g mercury/g wet wt, the mean concentration found in this study, at rates greater than 70 g/day, was estimated to be hazardous to huma n health.