Mercury exposure and potential health risks to Antarctic seabirds: A synthesis

Mercury (Hg) is an environmental concern in polar regions, including Antarctica-despite its remoteness and limited direct human activity. This review examines Hg exposure and the potential health risks for 31 species of Antarctic seabirds, using Hg toxicity benchmarks established for blood and converted for feathers. Blood and feathers Hg concentrations differed among families, species and diet. Squid-feeding species, such as albatrosses and some petrels, exhibited the greatest Hg concentrations, while crustacean feeders, such as Pygoscelis species, showed the lowest concentrations. Several Antarctic seabird populations showed blood Hg levels exceeding known toxicity thresholds, with 62 % of species surpassing the "no adverse health effect" level. Furthermore, 25 % of the species reviewed were categorized as being at moderate to high risk of Hg toxicity. While the majority (70 %) were considered at no or low risk, even relatively low Hg levels have been associated with adverse outcomes, including reduced egg volume and lower breeding success. Comparisons with Arctic seabirds of similar diets suggest comparable Hg burdens. Although overall Hg contamination in Antarctic seabirds remains low for most species, the potential for harmful effects may be amplified when combined with other stressors such as pollutants, disease, parasites, and climate change. This review also underscores a significant gap in available data: most existing studies are limited to a few species, locations, or isolated sampling years. Addressing these gaps will require broader, long-term monitoring efforts and international collaboration to improve understanding of Hg exposure and its ecological impacts in Antarctic seabird populations.