Differential Accumulation of Polychlorinated Biphenyl Congeners in the Aquatic Food Web at the Kalamazoo River Superfund Site, Michigan

A series of field studies were conducted to gain a better
understanding of the bioaccumulation and dynamics of
polychlorinated biphenyl (PCB) congeners in the aquatic
food web of the Kalamazoo River flood plain. Representative
species of passerine birds, mammals, fish, aquatic
plants, invertebrates, and colocated sediments were
collected from areas located within submerged portions
of the former Trowbridge impoundment and also from areas
located at an upstream reference location. In most
matrixes, total concentrations of PCBs were significantly
greater in the downstream study area compared to the
upstream reference location. Patterns of PCB congeners
varied among trophic levels due to selective bioaccumulation
of more chlorinated congeners in upper trophic level
organisms. There were no statistically significant differences
in total PCB concentrations among sampling grids within
either site or temporally among three sampling seasons
between May and September. The greatest total PCB
concentrations were detected in adult tree swallows (mean
= 8.7 mg/kg wet weight (ww)) and fish (mean = 4.4 mg/kg ww) collected from the former Trowbridge impoundment.
Concentrations of total 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) were greatest in egg, nestling,
and adult tree swallows collected from the former Trowbridge
impoundment. There was not a significant correlation
between concentrations of total PCBs and TEQs at either
site in the mammalian or avian food webs. The relative
potency of the mixture of PCBs, expressed as the ratio of
TEQs to total PCBs, increased with trophic position in
the avian and mammalian aquatic food webs located within
the former Trowbridge impoundment.