Concentrations of total mercury and methyl mercury were determined in sediment and fish collected from estuarine waters of Florida to understand their distribution and partitioning. Total mercury concentrations in sediments ranged from 1 to 219 ng/g dry wt. Methyl mercury accounted for, on average, 0.77% of total mercury in sediment. Methyl mercury concentrations were not correlated with total mercury or organic carbon content in sediments. The concentrations of total mercury in fish muscle were between 0.03 and 2.22 (mean: 0.31) micrograms/g, wet wt, with methyl mercury contributing 83% of total mercury. Methyl mercury concentrations in fish muscle were directly proportional to total mercury concentrations. The relationship of total and methyl mercury concentrations 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 seatrout contained the highest concentrations of mercury. Filtered water samples from canals and creeks that discharge into the Florida Bay showed mercury concentrations of 3-7.4 ng/L, with methyl mercury accounting for < 0.03-52% of the total mercury. Consumption of fish containing 0.31 microgram mercury/g wet wt, the mean concentration found in this study, at rates greater than 70 g/day, was estimated to be hazardous to human health.

During June and July, 2002, forty-seven stations were sampled within estuaries along the gulf coast of the state of Veracruz, MX, using a probabilistic survey design and a common set of response indicators. The objective of the study was to collect information to assess the condition of estuarine waters within the state of Veracruz, and to provide data that would strengthen future assessments of Gulf of Mexico estuaries. Samples for water quality, sediment contaminants, sediment toxicity, and benthic populations were collected in a manner consistent with EPA's National Coastal Assessment (NCA). Data were evaluated by comparing indicator measurements to tropical waters threshold values cited in US EPA's National Coastal Condition Report II, 2004, for tropical waters. In Veracruz, 75% of the area sampled rated poor for water quality, attributed primarily to high concentrations reported for chlorophyll a, and dissolved nutrients. One percent of the area exhibited poor sediment quality, based on PAH and metals concentrations. Compared to US estuaries of the Gulf of Mexico, water quality observed in Veracruz estuaries was more affected by nutrient over-enrichment. The probabilitistic nature of the survey design allowed for the comparison of the condition of Veracruz and the US GOM estuaries.

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Santa Rosa County, FL) that were held in cages in the C-ll1 canal and at selected sites in northeastern Florida Bay. Samples were collected during June and July 1995.

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