How does habitat use influence PFAS contamination in wildlife? Combining stable isotopes and GPS tracking in three gull species

Per- and polyfluoroalkyl substances (PFAS) are toxic and persistent compounds widely distributed in the environment and accumulate in top predators, including seabirds. Because of the biomagnification potentials of some PFAS, diet is thought to be a key exposure route for PFAS. However, other factors such as habitat use, may mask interspecific differences in PFAS exposure expected from trophic structure. Among seabirds, gulls are generalists that forage in both terrestrial and marine habitats, making them relevant models to concurrently investigate the influence of foraging habitats and trophic position on PFAS exposure. We combined plasma PFAS concentrations with GPS tracking and stable isotopes to define foraging habitats (δ¹³C; δ³⁴S; GPS) and trophic positions (δ¹⁵N) in three sympatric gull species breeding in France (Isle of Ré). In herring gulls (Larus argentatus), long-chain perfluoroalkyl carboxylic acids (PFCAs) were positively correlated with high trophic resources from marine habitats. We found compound- and sex-dependent relationships between PFAS concentrations and stable isotope values in lesser black-backed gulls (Larus fuscus), while no association was found with habitat use. No association was found between PFAS levels and stable isotopes in great black-backed gulls (Larus marinus). Our study suggests that coastal habitat could be a source of PFCA contamination and highlights that the influence of habitat use on gull exposure to PFAS varied depending on species, sex, and compounds.