Although lying far from extensive human industries and from major sources of pollution, the Arctic is threatened by major and increasing pollution risks. The rapid change of the cryosphere might indeed release large amounts of pollutants trapped in sea ice, permafrost and terrestrial glaciers over the last decades. The shrinking sea ice cover is also opening new shipping routes and thus increasing opportunities for polluting extractive human industries, targeting hydrocarbons, sea-floor minerals and unexploited fish stocks. The general warming of ocean water masses is also expected to affect the cycle of many pollutants, increasing the exposure of marine organisms. In addition, the Arctic region receives large amounts of pollutants emitted by mid-latitude northern countries transported to the Arctic by prevailing winds, ocean currents and rivers.

Among pollutants that have largely increased in the Arctic over the last decades, mercury (Hg) has raised major environmental concerns, both at the Arctic and global scales. Indeed, low concentrations of Hg in organisms can result in large health effects, ranging from minor physiological disorders to death, Hg acting for instance as endocrine disruptor, neurotoxic or affecting the immune system and gene expression. Beyond health, Hg impact individual reproduction and thus ultimately affect the population dynamics of various marine species.

In that context, several international initiatives and actions have been set up over the last decades to provide a better characterization and understanding of Hg concentrations, sources, temporal trends and toxicological effects in Arctic marine ecosystems (e.g. the Arctic Monitoring and Assessment Programme (AMAP) of the Arctic Council, the Canadian Northern Contaminants Programme, etc.).

In 2014, ARCTOX, a complementary coordinated pan-Arctic network has been set up in order to study the large scale contamination of Arctic seabirds and Arctic marine food-webs.

Seabirds are highly valuable species in this context. First because they are the most threatened group of birds in the world, with pollution being one of the major threat. Hg concentrations can exceed toxicity thresholds in some seabird species with subsequent effects on their reproduction and population dynamics, and a large-scale  understanding of their vulnerability to Hg is thus essential in a conservation perspective. Second because seabirds integrate and reflect the contamination of the entire food-chain on which they rely and therefore function as powerful indicators of the contamination of marine food webs. Their study thus provides information beyond their own contamination, about Hg contamination of marine ecosystems and its large-scale spatio-temporal variations. Third, because the seabird community has a wide, pan-Arctic distribution occupying contrasting habitats and thus allowing very large scale investigations to understand the contamination of Arctic marine ecosystems and underlying processes. 

Based on existing field campaigns led all over the Arctic by the research seabird community, ARCTOX thus aims to collect blood and feather samples every year at >60 Arctic breeding sites and >20 seabird species in order to 1/ evaluate seabird exposure to chemical contaminants year-round (both during summer and winter) and how different Arctic species and/or populations might be at risk. 2/ Understand the trophic, abiotic and spatial sources of this contamination. 3/ Use seabirds as bioindicators to map the pan-Arctic distribution of Hg in marine food webs and identify hotspots and coldspots of contamination. 4/ Evaluate temporal changes in seabird contamination, both at the population and Arctic scales.