Inter-annual variation in winter distribution affects individual seabird contamination with mercury

Céline Albert ,Vegard Sandøy Bråthen ,Jóhannis Danielsen ,Paco Bustamante ,Signe Christensen‐Dalsgaard ,Maria Gavrilo ,Yu V Krasnov ,Børge Moe ,Sébastien Descamps ,Tycho Anker‐Nilssen ,Þorkell Lindberg Þórarinsson ,Hallvard Strøm ,Geir Helge Systad ,Yann Kolbeinsson ,Sveinn Are Hanssen ,Alexander Cherenkov ,Paul M Thompson ,Tone K Reiertsen ,Bergur Olsen ,Kjell Einar Erikstad ,Grigori Tertitski ,Hálfdán H Helgason ,Jón Eínar Jónsson ,Erlend Lorentzen ,Magdalene Langset ,Jérôme Fort

doi:10.3354/meps13793

Abstract

Migratory seabirds are exposed to various pollutants throughout their annual cycle. Among them, mercury (Hg) is of particular concern given its large impact on animal health. Recent studies suggest that winter is a critical period for seabirds when contamination by Hg can be higher than at other times of year. However, individuals within and between species can have different migration strategies and winter distributions that could affect their exposure. Here, we combined multi-year individual tracking data and Hg measurements from 6 Arctic seabird species. We investigated whether inter-annual variations in individual winter contamination with Hg was related to seabird fidelity to a wintering site over years. First, our results show that Hg concentrations above the toxicity threshold (i.e. 5 µg g-1dry weight in feathers) were observed in variable proportions according to species (from 2% of northern fulmars to 37% of Brünnich’s guillemots). Second, individuals with high fidelity to a wintering ground had more similar Hg concentrations among years compared to individuals with low fidelity, suggesting an effect of their migratory strategy on Hg contamination. Further, we found that the directional change in wintering areas among years influenced seabird Hg contamination, highlighting an additional effect of seabirds’ winter distribution. More specifically, individuals migrating to the northwest direction of a previous wintering ground tended to be more contaminated compared to those moving to eastern directions. These results confirm spatial differences in Hg concentration throughout the North Atlantic-Arctic and an east-west gradient increase in Hg concentrations. Verifying this trend will require more large-scale ecotoxicological studies at smaller spatial resolution.

Highlights

Mercury (Hg) is a highly toxic pollutant for humans and wildlife, causing severe health impairments, even at low concentrations (e.g. Wolfe et al 1998, Tan et al 2009, Dietz et al 2019)
While some seabirds use the same wintering ground every year, others change and occupy different places from one year to the other. Such different strategies can have large effects on their exposure to environmental stressors, pollutants, which could in turn impact their contamination level, body condition, reproduction and their population dynamics
By combining for the first time the use of tracking devices on multiple species with Hg analyses, we demonstrated that inter-annual fidelity of seabirds to a wintering area affects their contamination level, with a major effect of the location of these areas in the North Atlantic and sub-Arctic

Summary

Introduction

Mercury (Hg) is a highly toxic pollutant for humans and wildlife, causing severe health impairments, even at low concentrations (e.g. Wolfe et al 1998, Tan et al 2009, Dietz et al 2019). Hg is naturally emitted by volcanoes or weathering of rocks (UNEP 2013), but anthropogenic activities have been responsible for an increase in Hg concentrations in the environment since the industrial revolution (e.g. a 3-fold increase in surface marine waters; Lamborg et al 2014). This pollutant is very problematic in aquatic environments, where it can be transformed into its most toxic form (methylmercury or MeHg) by microorganisms (Hsu-Kim et al 2013). Understanding the relationship between seabird distribution and contamination by Hg is important for the conservation of these species, with many populations declining and deserving special attention (Croxall et al 2012, Paleczny et al 2015)

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Conclusion