Contamination of ivory gulls (Pagophila eburnea) at four colonies in Svalbard in relation to their trophic behaviour

Abstract : The ivory gull (Pagophila eburnea) is a high-Arctic species considered endangered in most parts of its breeding range. Ivory gulls must cope with not only the reduction in sea ice cover triggered by climate change but also increasing contaminant loads due to changes in global contaminant pathways and the release of previously stored pollutants from melting snow and ice. This top predator may be affected by biomagnification processes of a variety of compounds with concentrations dramatically increasing from water to higher trophic levels. The objective of this study was therefore to assess the contaminant bioaccumulation of this species in four colonies located on Barentsøya, Svalbard, in link with its trophic behaviour. To that end, contaminants, including organochlorines (OCs), brominated flame retardants (BFRs), and perfluorinated alkyl substances (PFASs), were determined in the blood (plasma and whole blood) of ivory gulls sampled over several years. Carbon- and nitrogen-stable isotopes were also determined in different tissues (feathers, plasma and red blood cells, or whole blood) to infer the trophic level (δ15N) and feeding habitat (δ13C) during both the breeding and moulting periods. The most quantitatively abundant contaminants found in the ivory gull were p,p’-DDE (dichlorodiphenyldichloroethylene), RPCB (polychlorobiphenyl), and PFOS (perfluorooctane sulphonate). Several compounds including most of the PFASs, trans-nonachlor, cis-nonachlor, and BDE-28 were correlated with nitrogen values. This study highlighted variability in trophic behaviour among individuals during the breeding and the moulting periods. Overall, similar feeding habitats and strategies were used between breeding sites which was echoed by similar contaminant levels.