INFLUENCE OF WATER CHEMISTRY ON MERCURY CONCENTRATION IN LARGEMOUTH BASS FROM FLORIDA LAKES

Harvestable-size largemouth bass Micropterus salmoides were collected from 53 Florida lakes to determine relationships between mercury concentration in fish and physical and chemical lake characteristics. Diverse lakes with a broad range of sizes (15-181,000 hectares), pH (3.6-9.1), and alkalinities (1.2-128 mg/L as CaCO3) were sampled. Total mercury concentrations in axial muscle of individual fish ranged from 0.04 to 2.04 mu/g wet weight and were positively correlated with fish age (strongest correlation) and size. There was no difference in the rate of mercury accumulation by age between the sexes, even though females grew faster. Chemical characteristics of lakes strongly influenced the bioaccumulation of mercury in largemouth bass. Mercury concentrations, standardized to age-3 fish for comparison among lakes, ranged from 0.04 to 1.53 mug/g and were negatively correlated with alkalinity, calcium, chlorophyll a, conductance, magnesium, pH, total hardness, total nitrogen, and total phosphorus. No significant correlations were observed between the standardized fish mercury concentration and lake color, secchi transparency, tannic acid, or surface area. Linear regression revealed that pH accounted for 41% of the variation in the standardized fish mercury concentration. Multiple regression revealed that chlorophyll a and alkalinity accounted for 45% of the variation in the standardized fish mercury concentration. Mercury concentrations were significantly higher in lakes with either pH less than 7, alkalinity less than 20 mg/L as CaCO3, or chlorophyll a less than 10 mug/L.