INFLUENCE OF FEEDING-HABITS ON ORGANOCHLORINE CONTAMINANT ACCUMULATION IN WATERFOWL ON THE GREAT-LAKES

Zebra mussels (Dreissena polymorpha) are an important component of ben thic communities in the Great Lakes and are exploited by a host of pre dators, including waterfowl. In this study, we analyze diet content an d stable isotope and organochlorine contaminant patterns in Lesser Sca up (Aythya affinis), Greater Scaup (Aythya marila), Bufflehead (Buceph ala albeola), Redhead (Aythya americana), Canvasback (Aythya valisiner ia), and Mallard (Arras platyrhynchos) collected from three sites (Fig hting Island, western Lake Erie, Big Creek) in the lower Great Lakes. Lesser and Greater Scaup from Fighting Island were classified as eithe r zebra mussel (greater than or equal to 67% of diet) or macrophyte (g reater than or equal to 85% of diet) consumers. Bufflehead, Canvasback , Mallard, and Redhead consumed mainly (greater than or equal to 89%) macrophyte at Fighting Island. Zebra mussel was the principal food of Lesser Scaup (>99%), Greater Scaup (97%), and Bufflehead (72%) in west ern Lake Erie. Stable isotope analysis revealed enrichment of delta(15 )N in Lesser Scaup (greater than or equal to 2.24 parts per thousand), Greater Scaup (greater than or equal to 1.28 parts per thousand), and Bufflehead (greater than or equal to 0.63 parts per thousand) that ex ploited mussels relative to conspecifics with macrophyte diets and rel ative to mussel prey. Representative contaminants of low (hexachlorobe nzene [HCB]), moderate (PCB [polychlorinated biphenyl] 153), and high (PCB 180) hydrophobicity were examined in waterfowl. Lipid-normalized concentrations of PCBs 153 and 180 were significantly higher in scaup and Bufflehead that consumed Dreissena than in individuals that ate ma inly macrophytes. Among taxa that consumed primarily Dreissena, concen trations of PCBs 153 and 180 were significantly higher in individuals from Lake Erie than in those Fighting Island. Principal components ana lysis revealed broad differences in contaminant patterns of waterfowl based principally on diet. Results from this study illustrate that Dre issena has become a primary food source of some waterfowl in the lower Great Lakes and serves as an effective conduit for transfer of persis tent organic contaminants to higher trophic levels.