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Mercury in fish tissue of Idaho lakes vs. those of the Northeastern United States as it relates to the moderating effects of selenium
Citation:
PETERSON, S. A., A. T. HERLIHY, AND D. A. Essig. Mercury in fish tissue of Idaho lakes vs. those of the Northeastern United States as it relates to the moderating effects of selenium. Presented at SETAC, New Orleans, LA, November 19 - 23, 2009.
Impact/Purpose:
The primary methyl-mercury (MeHg) exposure mode to wildlife and humans is through the consumption of aquatic organisms, particulary fish.
Description:
The primary methyl-mercury (MeHg) exposure mode to wildlife and humans is through the consumption of aquatic organisms, particulary fish. Selenium has been demonstrated to moderate the toxicity of MeHg in every test animal type examined to date. A molar ratio of Se:Hg >1 appears to be significant relative to protection against MeHg toxicity. We sampled whole body fish tissue from 51 western lakes (Idaho) and 74 northeastern US Lakes (Maine, New Hampshire, Vermont, Connecticut, Rhode Island, Massachusetts, New York and New Jersey) for selenium and mercury concentrations. Sample lakes were selected using a probability design so they are representative of all lakes in the study region. Mean fish tissue mercury concentrations exceeded the human fish tissue criterion (0.3 ug/g) in 25% of the Idaho lakes and 7% of the Northeastern Lakes. Mercury concentrations were highest in piscivorous fish species (e.g. bass, pike, walleye). Selenium to mercury molar ratios (Se:Hg) were >1 in 94% of the fish sampled in the Northeast and 83% of the fish sampled in Idaho. Among fish species common to both western and northeastern lakes, bass (Micropterus salmoides) appear to have the greatest potential for mercury toxicity risk to consumers due to their high mercury content and lower Se:Hg molar ratios. The Se:Hg molar ratio in bass tissue in 35% of our survey lakes that contained bass was <1. In the Northeastern lakes with bass, less than 1% of the lakes had a Se:Hg molar ratio <1. Thus, the expectation that, due to the scarcity of Se in the regional lithosphere, northeastern lakes might pose a greater mercury toxicity risk relative to their fish tissue Se:Hg molar ratio proved to be invalid.