Effects of trophic position and lipid on organochlorine concentrations in fishes from subarctic lakes in Yukon Territory
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abstract
Concentrations of organochlorines in lake trout (Salvelinus namaycush), burbot (Lota lota), and northern pike (Esox lucius) from subarctic lakes in Yukon Territory varied significantly among populations, and these differences could not be ascribed to size or age of the fishes. For each species, lipid content and trophic positioning (measured by stable nitrogen isotope ratios; delta 15N) were significantly different across populations, and the latter differences could not be attributed to variable delta 15N at the base of the food webs. Across lakes, concentrations of up Sigma PCB, Sigma DDT, chlorinated bornanes (CHB), chlordane ( Sigma CHL), chlorobenzenes ( up Sigma CBZ), and hexachlorocyclohexane ( Sigma HCH) in lake trout and northern pike muscle and burbot liver were significantly related to their delta 15N. The slopes of these log organochlorine - delta 15N relations were greatest for more lipophilic contaminants ( Sigma PCB, Sigma DDT, CHB), indicating that they bioaccumulate to a greater degree than less lipophilic contaminants. Lipid significantly predicted organochlorine concentrations both within and among populations of lake trout, and the slopes did not vary significantly with contaminant lipophilicity. Among-lake differences in Sigma HCH in trout muscle were removed by adjusting concentrations by the covariate lipid. Lipid-adjusted concentrations of CHB, Sigma PCB, Sigma DDT, Sigma CHL, and Sigma CBZ in lake trout remained significantly different between lakes, and these differences were attributed to variable food chain lengths.
