Mercury levels in Ontario mink and otter relative to food levels and environmental acidification

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Abstract
Tissue mercury levels were determined in 94 mink and 84 otter collected from five study areas in Ontario during the 1983–1984 and 1984–1985 trapping seasons. The level of Hg in tissues of both mink and otter followed the order of liver, kidney > muscle > brain. There was no observed relationship between age, sex, or selenium content and tissue Hg levels in mink or otter within a study area. Tissue Hg levels in mink and otter were significantly different among locations. For example, the mean Hg concentrations in mink liver from the English River, Turkey Lakes, Muskoka, Sudbury, and Cambridge areas were 2.55, 2.36, 2.17, 0.56, and 0.14 μg/g, respectively. Mercury levels in fish and crayfish from the study areas followed a similar pattern. Mink and otters are, therefore, sensitive bioindicators of environmental Hg levels. The results contradict the general hypothesis of elevated Hg levels in biota from acid-stressed ecosystems, and suggest that environmental variables other than pH play a major role in governing biotic metal levels.