The trophodynamics of PCBs, including mono- and non- ortho congeners, in the food web of North-Central Lake Ontario

The distribution of polychlorinated biphenyls (PCBs) in the food-web of Lake Ontario was studied to determine the parameters that control the trophodynamics of PCB congeners; including toxic non- ortho and mono- ortho PCBs. ‘Biomagnification’ of PCBs was evident in the food-web as total PCBs increased through trophic levels when concentrations were calculated on both a wet wt. and lipid weight basis; although there was no evidence of biomagnification between forage fish and piscivorous fish. Biomagnification was greatest for congeners with log octanol-water partition (log K ow) coefficients between 6 and 7.5. Non- ortho congeners 77 and 126, and congener 151 were not biomagnified to the extent of other congeners with similar K ow, which was attributed to high rates of metabolic clearance of these compounds. The Toxic Equivalent Quantities (TEQs) associated with non- ortho and mono- ortho PCBs increased throughout the Lake Ontario food-web. The high TEQ observed in herring gull eggs was primarily the result of very high concentrations of congener 126 in this component of the food web.