 By Lee Harding
PhD Thesis Abstract 2002
Gifu University, JapanIn a study of contaminants during 1991 to 1995, an unusual pattern of organochlorine compounds was noticed in some ospreys from the Columbia and Fraser River basins. The pattern, characterized by high concentrations of the more highly chlorinated dioxins and furans, was not present in the fish, their prey, and there were no known local sources. To determine whether this pattern derived from local sources or was accumulated on the wintering range, mink, river otters, martens, and wolverines were collected at several locations in the Columbia and Fraser River basins during 1995-1997. Secondary objectives were to determine whether the endocrine disrupting contaminants identified in the aquatic mustelids were associated with physiological or reproductive anomalies, and to evaluate the four mustelid species as indicators of ecosystem health. Patterns of PCB contamination varied between the two aquatic species and also within a species, among regions. In marten livers, no organochlorine residues were detectable. In wolverine livers, no organochlorine residues were detectable except for trace amounts of DDE in four of 11 specimens. Overall, the heavy metal concentrations in both livers and kidneys were generally low and within the range of values reported for ranch and wild mustelid populations. The one notable exception was a female otter with 7.2 µg/g dry weight of lead captured near a lead smelter at Trail, B.C.. Nutritional conditions varied slightly among collection regions, but showed no relationships with contaminant burdens. About 10% of otters and mink had gross abnormalities of digestive, renal, endocrine, or reproductive systems, but these were unrelated to contaminant concentrations. However, there were significant negative correlations between PCB concentrations and both baculum length and weight in juvenile mink, and between TEQ (toxic equivalent quotients, in which the sum of the toxicities of all organic compounds is expressed in terms of the equivalent toxicity of 2,3,4,7 tetrachlorodibenzo-dioxin) and baculum length in otters. Reduced baculum size, as an indicator of a broader range of reproductive and other health effects, together with a range of endocrine disrupting contaminants, suggests that the more highly contaminated individual mink and otters may be adversely affected in portions of these river systems. From these studies, it was shown that the mink and otters had the same unusual contaminant pattern as observed in the ospreys, proving the existence of a local source of highly chlorinated dioxins and furans. Mink and otters had smaller reproductive organs with increasing concentrations of certain endocrine disrupting contaminants. Martens and wolverines had only very low concentrations of contaminants. Contaminants concentrations in mink and marten livers can be used as indicators of aquatic ecosystem health, but wolverines and river otters are unsuitable as indicators because of their declining populations and uncertain conservation status. Baculum size in juvenile aquatic mustelids can be used as indicators of effects of endocrine-disrupting contaminants if collections are carefully timed to coincide with the post-natal period during which these effects may be observed; in older animals, the rapidly growing sexual organs obscure such effects. Management implications for the conservation of wild mustelids are discussed. The full text of the thesis is available at http://www.SciWrite.ca/Toxicology.htm.
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