Effects of trophic position and lipid on organochlorine concentrations in fishes from subarctic lakes in Yukon Territory

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; δ15N) were significantly different across populations, and the latter differences could not be attributed to variable δ15N at the base of the food webs. Across lakes, concentrations of ΣPCB, ΣDDT, chlorinated bornanes (CHB), chlordane (ΣCHL), chlorobenzenes (ΣCBZ), and hexachlorocyclohexane (ΣHCH) in lake trout and northern pike muscle and burbot liver were significantly related to their δ15N. The slopes of these log organochlorine - δ15N relations were greatest for more lipophilic contaminants (ΣPCB, ΣDDT, 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 ΣHCH in trout muscle were removed by adjusting concentrations by the covariate lipid. Lipid-adjusted concentrations of CHB, ΣPCB, ΣDDT, ΣCHL, and ΣCBZ in lake trout remained significantly different between lakes, and these differences were attributed to variable food chain lengths.