Levels of Polychlorinated Biphenyls, Including Coplanar Congeners, and 2,3,7,8-T 4 CDD Toxic Equivalents in Double-crested Cormorant and Herring Gull Eggs From Lake Erie and Lake Ontario: A Comparison Between 1981 and 1992

Abstract

Eggs of double-crested cormorants and herring gulls collected from Lakes Erie and Ontario during 1981 and 1992 were analyzed for PCB congener concentrations, including non-ortho congeners 77, 126, and 169. Total PCB in herring gulls, measured as Aroclor 1254/1260, was significantly lower in 1992, although differences in chemical concentrations in Lake Erie birds were not of the same magnitude as those observed in Lake Ontario. Changes in concentration of total PCB in cormorant populations were not significant in Lake Ontario, and only a small change was observed in Lake Erie cormorants. In 1981, cormorants and herring gull eggs were similarly contaminated in Lake Ontario and Lake Erie, but in 1992, Lake Erie eggs were significantly more contaminated than those from Lake Ontario. An examination of changes in concentrations of individual congeners suggested that in cormorants, the decrease in PCB concentrations was due primarily to the loss of low K ow congeners. All congeners, however, contributed to the decline of PCBs in herring gulls. Toxic equivalents (TEQs) estimates revealed that congener 126 dominated the TEQs in both species in Lake Ontario and Lake Erie, and were highest in herring gulls. Although estimates of total TEQs in herring gulls in both lakes were lower in 1992, there was little change in TEQs in double-crested cormorants. These results support the conclusion that chemical accumulation patterns are regulated to some degree by both ecological and limnological processes.