Food Chain Structure in Ontario Lakes Determines PCB Levels in Lake Trout (Salvelinus namaycush) and Other Pelagic Fish

Abstract

The trophic structure of pelagic communities in lakes of glaciated regions is highly variable due to restricted dispersal of glacial relict taxa and recent species introductions. Much of the enormous between-lake variability in PCB levels in lake trout flesh (15–10 000 ng/g) from the St. Lawrence system results from differences in the length of pelagic food chains. Ontario Ministry of the Environment data (1978–81) on PCB concentrations in lake trout flesh indicate that PCB concentrations increased with the length of the food chain and tissue lipid content, and decreased with distance north of urban-industrial centres. Each trophic level contributed about a 3.5-fold biomagnification factor to the PCB concentrations in the trout, and the lipid content of the trout flesh increased by a factor of 1.5 for each additional trophic level. An empirical model capable of predicting PCB levels in pelagic salmonids and forage fish (smelt and coregonids) indicated that biomagnification of small atmospheric inputs of persistent lipophilic contaminants can explain the frequent occurrence of high levels of contaminants in some biota from remote areas, and that species introductions that lengthen food chains will lead to significant increases in levels of atmospherically dispersed persistent organic contaminants in top predators.

Bioaccumulation and differential partitioning of polychlorinated biphenyls in freshwater, planktonic food webs

“…In an expanded analysis of the data used by Rasmussen et al (1990), Bentzen et al (1996) found that PCB concentrations in lake trout (Salvelinus namaycush) from different lakes were a function of lipid content, but the intercepts of the regressions differed between lakes. This was attributed to food chain effects and (or) different loading of PCB.…”

Resilience and Restoration of Lakes

“…Organochlorine compounds are persistent toxic pollutants that affect many lakes. Although the more pernicious organochlorine compounds are no longer manufactured in the United States, significant amounts of some compounds still cycle within lakes and enter lakes from the atmosphere (Rasmussen et al 1990, Stow et al 1995. Acid precipitation has several negative impacts on lakes (Schindler et al 1991), including a surprising interaction with stratospheric ozone depletion (D.W. .…”

Bioaccumulation and differential partitioning of polychlorinated biphenyls in freshwater, planktonic food webs

“…Other, indirect approaches have also led to the conclusion that biomagnification of lipophilic chemicals via the food web is a major contributor to their accumulation in biota at higher trophic levels. Rasmussen et al (1990) concluded that concentrations of PCB in top predators from different lakes increased with increasing length of the food chains, a result attributed to biomagnification. Russell et al (1995) showed that concentrations of some PCBs were greater in white bass (Morone chrysops) than in their prey, emerald shiner (Notropis atherinoides), in Lake Erie, i.e., their biomagnification factors (BMFs) were > 1.…”