Persistent organic pollutants and stable isotopes in seabirds of the Rocas Atoll, Equatorial Atlantic, Brazil

Pollution is a key factor in efforts to conserve seabirds and their habitats. The Marine Biological Reserve of Rocas Atoll hosts the largest population of seabirds (~23 000 individuals) breeding in Brazilian waters. In the present study at Rocas Atoll, liver samples were collected from dead individuals of five species (adults and nestlings): Masked Booby Sula dactylatra, Brown Booby Sula leucogaster, Brown Noddy Anous stolidus, Black Noddy Anous minutus, and Sooty Tern Onychoprion fuscatus. They were analyzed for three persistent organic pollutants (POPs): polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers. Carbon and nitrogen stable isotopes (δ13C and δ15N) were also analyzed to assess feeding and foraging habits. PCBs (3.37-189 ng·g-1), OCPs (DDTs, 0.5-23.1 ng·g-1), and hexachlorobenzene (0.31-12.3 ng·g-1) were predominant overall, and results were generally consistent with previous studies. Despite the low levels of contaminants, intraspecific stratification was found with lower concentrations in nestlings compared to adults, as expected. Stable isotopes revealed that differences in POP levels and PCB profiles were associated with diet and foraging patterns. Low levels of POPs at Rocas Atoll were consistent with patterns observed in studies of other low-latitude and high-latitude seabirds.