Organochlorine and heavy metal contaminants in wild mink in western Northwest Territories, Canada.

The mink (Mustela vision) is a top trophic level species that readily bioaccumulates environmental pollutants and is considered to be a sensitive indicator of ecosystem health. Spatial trends in levels of organochlorine and heavy metal contaminant burdens were determined from 1991 to 1995 for wild mink from western Northwest Territories (NWT), Canada. Tissue samples from 207 mink from seven communities were analyzed for residues of 63 organochlorines and 10 heavy metals. All groups of organochlorines were detected in mink livers at relatively low levels; maximum community means were 9.52 ng/g sigma DDT and 73.07 ng/g sigma PCB (sum of 43 congeners). There was a general trend of decreasing organochlorine burdens along a northerly or westerly gradient for some groups of compounds, primarily sigma DDT, sigma PCB, sigma chlordane and dieldrin. Toxic equivalents (TEQs) of mink liver tissue were low, with the maximum community mean of 0.28 pg/g wet weight (5.5 pg/g lipid weight). Levels of heavy metal burdens in liver and kidney tissues were found to be relatively low, with the exception of Hg, which was found at moderate levels. There was no obvious geographic trend to the pattern of heavy metal burdens. The available evidence suggests that long-range atmospheric transport is the main source of the organochlorine contaminants observed. Local conditions (geology, water and soil chemistry, diet, etc.) may determine heavy metal burdens. Levels of contaminants in NWT mink appear to be one to two orders of magnitude lower than levels observed to cause reproductive impairment, reduced survival of kits, or lethality in adult mink. In the western NWT mink may be the best indicator to assess trends in environmental contaminants and ecosystem health; periodic monitoring is recommended.

Environmental contaminants in caribou in the Northwest Territories, Canada.

Caribou (Rangifer tarandus) are strict herbivores with a winter diet consisting primarily of lichen. This simple food chain makes caribou a good species for monitoring changes in arctic terrestrial ecosystem contamination. The defined ranges of herds across the Northwest Territories (NWT) also enables examination of spatial trends in contaminant exposure. Caribou were collected from five locations in the first half of a study designed to examine levels of a broad spectrum of organochlorine, heavy metal, and radionuclide contaminants. A wide range of contaminants were detected, with most compounds found at relatively low levels. In general, organochlorine residues were significantly lower in caribou from the mainland Bathurst and Qamanirjuaq (Arviat) and the Southampton Island herds than in caribou from Cape Dorset and Lake Harbour on southern Baffin Island. Moderate levels of hexachlorobenzene (HCB) and alpha-hexachlorocyclohexane (alpha-HCH) were detected at all five study sites. HCB residues ranged from a lipid corrected mean of 32.83 ng/g in fat of Bathurst caribou to 129.41 ng/g in Lake Harbour animals. Alpha-HCH levels ranged from 8.11 ng/g in Bathurst animals to 37.9 ng/g in Cape Dorset caribou. Total polychlorinated biphenyl (sigma PCB) residues ranged from 6.24 ng/g in fat of Arviat caribou to 31.68 ng/g in Cape Dorset animals. Congeners 153 and 138 were the most dominant of the 43 congeners tested. Metal levels were also relatively low with the exception of cadmium, which had community means of 9.68- 33.87 micrograms/g in kidney tissue and 1.96-4.39 micrograms/g in liver tissue. Moderate levels of cesium-137 were detected, with community means of 33.2-184.1 Bq/kg in muscle tissue. Long-range atmospheric transport appears to be the primary source of the contaminants detected in this study.

Environmental contaminants in wild mink in the Northwest Territories, Canada.

As a top trophic level species that readily bioaccumulates environmental pollutants, the mink (Mustela vison) is considered to be a sensitive indicator of ecosystem health. Here we report on the first 2 years of a 4-year program established to examine organochlorine and heavy metal residues in wild mink from western Northwest Territories (NWT), Canada. Tissue samples taken from up to 24 mink harvested from each of five sites in 1991-92 and 1992-93 were analyzed for residues of a suite of 63 organochlorines in fat and liver samples, including 43 polychlorinated biphenyl (PCB) congeners and 20 pesticides, and residues of 10 heavy metals in liver and kidney samples. Overall, contaminant levels were low in comparison with levels in other mink studied in North America. Sigma PCB residues (sum of 43 congeners) ranged from a mean of 5.32 ng/g wet weight in the livers of Inuvik mink (the most northerly collection site) to 27.67 ng/g in mink from Fort Smith (the most southerly collection site). There appeared to be no differences in organochlorine burden between sexes. Heavy metal residues were also comparatively low, with the exception of total mercury, which was at moderate levels (community means of 1.16-3.30 micrograms/g wet wt. in liver samples). There was a distinct trend of decreasing organochlorine contaminant burdens with increasing latitude, but no trend in heavy metal burdens was evident. There was a doubling of mean sigma PCB levels in Inuvik mink from 5.32 ng/g wet weight in 1991-92 to 10.69 ng/g in 1992-93. Population indices derived from age and sex ratios of the harvest, coupled with comparatively low levels of contaminants, suggest little or no effects on mink reproduction or population health as a result of these contaminants. Long-range atmospheric transport is probably the major source of most of the contaminants. Additional collections will further elucidate spatial and temporal trends in contaminant levels in NWT mink.