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Mercury and PCB residues in Massachusetts river otters: Comparisons on a watershed basis

John F Organ, University of Massachusetts Amherst


Mercury and polychlorinated biphenyl (PCB) residues in livers of trapper harvested river otters from Massachusetts were evaluated. Two-hundred and ten river otters collected during 1986 and 1987 were composited into 103 samples and analyzed. Comparisons among 20 watersheds were made using 96 samples. Mercury residues were detected in all samples and ranged from 0.45 to 4.82 ppm wet weight with an arithmetic mean of 1.93 ppm. PCB residues were detected in all but 3 samples and ranged from none-detected (ND) to 22.00 ppm with a geometric mean of 1.03 ppm wet weight. Lipid-adjusted total PCBs ranged from ND to 6.47 ppm with a geometric mean of 0.36 ppm. Significant differences (P $<$ 0.05) were detected among watersheds for mercury, total PCBs, and lipid-adjusted total PCBs. A significant difference between years was detected for lipid-adjusted total PCBs. Tukey's HSD test indicated the Charles, Blackstone, and Parker watersheds had significantly higher otter liver mercury residues than the Westfield, Quinnebaug, Deerfield, Connecticut, Buzzard's Bay, and North Coastal watersheds. Juvenile otters had significantly (P = 0.007) lower mercury residues than older otters. Tukey's HSD test indicated the Housatonic, Buzzard's Bay, Merrimack, Concord, and Charles watersheds had significantly higher otter liver total PCB residues than 13 of the remaining 15 watersheds sampled. Juvenile otters had significantly (P = 0.02) lower levels of total PCBs than older otters. Correlations between otter residues and whole-body fish residues on a watershed basis showed a strong relationship between fish and otter mercury residues. River otters can be used to assess general background mercury and PCB contamination levels on a watershed basis to prioritize and justify more intensive contaminant monitoring efforts. However, caution in interpreting PCB residue analyses is strongly recommended because of high variances associated with watershed means. River otter populations do not appear to be at risk singly from either mercury or PCB contamination in Massachusetts. Population monitoring should evaluate potential additive or synergistic effects of mercury in combination with PCBs in certain watersheds. Laboratory research is needed to document effect levels of environmental contaminants in river otters.

Subject Area

Forestry|Environmental science

Recommended Citation

Organ, John F, "Mercury and PCB residues in Massachusetts river otters: Comparisons on a watershed basis" (1989). Doctoral Dissertations Available from Proquest. AAI9011778.