ACCUMULATION OF 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN EQUIVALENTS BY DOUBLE-CRESTED CORMORANT (PHALACROCORAX-AURITUS, PELICANIFORMES) CHICKS IN THE NORTH-AMERICAN GREAT-LAKES

Concentrations of polychlorinated biphenyls (PCBs), and 2,3,7,8-tetrac hlordibenzo-p-dioxin equivalents (TCDD-EQ) were determined in eggs and chicks of double-crested cormorants (DCC) which were collected in 198 9 from eight locations in the Laurentian Great Lakes. The mean biomagn ification factor (BMF) from forage fish to eggs was found to be 31.3. Absolute and relative concentrations as well as rates of accumulation of total concentrations of PCBs and TCDD-EQ were measurable in all of the samples. The concentrations of both PCBs and TCDD-EQs decreased im mediately upon hatching of chicks, due to growth dilution. Initial dec reases in absolute masses of TCDD-EQ in chicks were also observed, whi ch indicates that there can be significant elimination of these compou nds during early development. The initial rates of accumulation by chi cks were dependent only on the mass of fish consumed. After the chicks began thermoregulating, the rates of accumulation, expressed as a con centration, normalized to body weight, became greater. Rates of accumu lation of both PCBs and TCDD-EQ were correlated with their respective concentrations in forage fish consumed by the chicks. The relative pot ency, expressed as the ratio of the concentration of TCDD-EQ to that o f total PCBs was calculated to determine if there was significant trop hic-level enrichment of the TCDD-EQs, relative to total concentrations of PCBs. A significant enrichment was observed at the more and less c ontaminated locations, but the degree of enrichment was greater at the less contaminated locations (26 vs 72 mug/g). (C) 1994 Academic Press , Inc.