Concentrations and patterns of organochlorines (OCs) and perfluoro-alkyl substances (PFASs) in eggs of two Arctic seabird species and their relationship with eggshell thickness

Abstract

Despite the remoteness of the Arctic, long-range transport of anthropogenic organohalogenated contaminants (OHCs) has led to their detection at high concentrations in various Arctic animals for decades. Seabirds have been commonly used as biomonitors of OHCs, and the current study investigated the concentrations and patterns of organochlorines (OCs) and perfluoro-alkyl substances (PFASs) in eggs of two Arctic seabird species, namely the Brünnich’s guillemot (Uria lomvia) and the ivory gull (Pagophila eburnea). In addition, stable isotopes of carbon and nitrogen were analysed in the eggs and used as proxies for feeding habitat and trophic level, respectively. The Brünnich’s guillemot is one of the most abundant seabird species breeding in the Arctic, and feeds mainly on prey at lower trophic levels. The ivory gull is a rare High Arctic seabird species roaming in ice filled waters positioned at the top of the Arctic food web. Unlike the Brünnich’s guillemot, the ivory gull has been less frequently monitored. This is the second study to report contaminant concentrations from the Norwegian and Russian Arctic. During the period 2018-2022, a total of 20 Brünnich’s guillemot eggs were collected from two locations (Bjørnøya and Kongsfjorden) within the Norwegian Arctic, and a total of 13 ivory gull eggs were collected from two locations (Nordaustlandet and Uyedineniya) within the Norwegian and Russian Arctic. In Brünnich’s guillemot eggs, we reported differences in the concentration of several contaminant groups between the two locations, while ivory gull eggs exhibited lower differences across sampling areas. Compared to Brünnich’s guillemot eggs, ivory gull eggs showed levels of OCs and PFASs 21 and 2.6 times higher, respectively. Additionally, the ivory gull had higher values of both carbon and nitrogen stable isotopes, reflecting their higher tropic position and stronger connection to the pelagic ecosystem compared to Brünnich’s guillemots. Our results indicated decreasing concentrations of several major contaminants over the last decade in both species. Moreover, we investigated the association between eggshell thickness and contaminants as potential drivers of the population declines observed over the last decades in the Brünnich’s guillemot and the ivory gull. For both species, the lack of correlations observed between OHC concentrations and eggshell thickness does not support contaminant-induced eggshell thinning. Although this was expected for the Brünnich’s guillemot, the ivory gull has previously been linked to contaminant-induced eggshell thinning. This result might indicate better outcomes for the species at the population level, however, other stressors such as climate change continue to threaten seabird populations.