CONGENER-SPECIFIC POLYCHLORINATED BIPHENYL PATTERNS IN EGGS OF AQUATIC BIRDS FROM THE LOWER-LAGUNA-MADRE, TEXAS

Eggs from four aquatic bird species nesting in the Lower Laguna Madre, Texas, were collected to determine differences and similarities in th e accumulation of congener-specific polychlorinated biphenyls (PCBs) a nd to evaluate PCB impacts on reproduction. Because of the different t oxicities of PCB congeners, it is important to know which congeners co ntribute most to total PCBs. The predominant PCB congeners were 153, 1 38, 180, 110, 118, 187, and 92. Collectively, congeners 153, 138, and 180 accounted for 26 to 42% of total PCBs. Congener 153 was the most a bundant in Caspian terns (Sterna caspia) and great blue herons (Ardea herodias) and congener 138 was the most abundant in snowy egrets (Egre tta thula) and tricolored herons (Egretta tricolor). Principal compone nt analysis indicated a predominance of higher chlorinated biphenyls i n Caspian terns and great blue herons and lower chlorinated biphenyls in tricolored herons. Snowy egrets had a predominance of pentachlorobi phenyls. These results suggest that there are differences in PCB conge ner patterns in closely related species and that these differences are more likely associated with the species' diet rather than metabolism. Total PCBs were significantly greater (p < 0.05) in Caspian terns tha n in the other species. Overall, PCBs in eggs of birds from the Lower Laguna Madre were below concentrations known to affect bird reproducti on.