Evidence of continued exposure to legacy persistent organic pollutants in threatened migratory common terns nesting in the Great Lakes

Persistent organic pollutants (POPs) accumulate in the food web of the Great Lakes ecosystem, causing concern that these chemicals play a role in the decline of avian species such as colonial-nesting waterbirds. In this study, samples from four life stages of the common tern (Sterna hirundo), a threatened species in New York State, were collected post-mortem in the Buffalo-Niagara region (United States). Brains (n = 26) and livers (n =27) were analyzed for polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and the insecticide p,p’-dichlorodiphenyltrichloroethane (DDT) and its two metabolites p,p’-dichlorodiphenyldichloroethylene (DDE) and p,p’-dichlorodiphenyldichloroethane (DDD). Detectable concentrations of PCBs and PBDEs were observed in all samples; concentrations of total PCBs ranged from 5.59 to 2,490 ng/g wet weight (ww), total PBDEs ranged from 1.09 to 494 ng/g ww, and DDE metabolites ranged from 0.56 to 637 ng/g ww. Analysis of the primary food source for terns in the Buffalo-Niagara region, emerald shiners (Notropis atherinoides), revealed that all three classes of POPs had similar contaminant profiles in the fish to those in the brains and livers of tern samples. Overall, small chicks contained greater concentrations of pollutants than medium chicks and juveniles, likely from maternal loading to eggs. These results underline the persistence of these legacy contaminants in the Great Lakes, despite their banning, and their biomagnification in threatened species through food web interactions.