The distribution of mercury across the North Atlantic

Mercury is a particularly toxic metallic element, making it crucial to better understand its spatial distribution in the environment.

In a recent study published in Proceedings of the Natural Academy of Sciences, an international network of researchers, led by the Littoral, Environment and Societies Laboratory (LIENSs - UMR 7266) and the Norwegian Polar Institute, used seabirds as bioindicators to map the broad-scale distribution of mercury across the North Atlantic.


Mercury (Hg), although a natural element, has seen its concentrations greatly increased in the environment over the past two centuries due to the rise in human activities and fossil fuel combustion. At high concentrations, it becomes toxic to living species, including humans, with known effects on behavior, reproduction, and the physiology of organisms. Therefore, international bodies closely monitor mercury concentrations in the environment to regulate its emissions.


To protect natural habitats and animal populations, it is crucial to better understand the spatial distribution of this pollutant. However, obtaining this knowledge is often challenging in marine organisms, due to technical limitations and financial costs.

In this study, seabirds were used as bioindicators to track and map Hg concentrations in the marine environment. Through an international collaboration between the ARCTOX network (monitoring Hg in seabirds on a pan-Arctic scale) and SEATRACK (monitoring seabird spatial distribution at sea), a total of 837 birds from seven species and 27 different colonies were monitored over four years. Hg concentration was measured in the feathers of each individual, and their spatial distribution was determined using geolocation systems.


The results highlight the wide-scale spatial distribution of Hg across the North Atlantic. They reveal a longitudinal gradient of measured concentrations, which are lower in the European part of the North Atlantic and the Arctic. Specifically, mercury hotspots were identified south of Greenland and east of Canada, where concentrations are up to three times higher than in the Barents Sea (Norway) or the Kara Sea (Russia).

This spatial distribution suggests an influence of ocean currents and the melting of the Greenland ice sheet on the distribution of Hg in food chains in the North Atlantic. Most importantly, it provides essential knowledge to support international bodies aiming to regulate mercury pollution globally. This study continues today within the framework of the ARCTOX network and long-term monitoring by the CNRS to assess how this Hg distribution and identified contamination hotspots have changed over the past 10 years and will continue to evolve in the future.

Reference:
Seabirds reveal mercury distribution across the North Atlantic.
Proceedings Of The National Academy Of Sciences Of The United States Of America, published on May 13, 2024.