Mercury, methylmercury, and its fractions at the base of the trophic pyramid of the maritime Antarctic ecosystem of Admiralty Bay.

Mercury (Hg) pollution in polar regions is a critical environmental concern, exacerbated by glacier melting due to climate change. This study investigated the impact of glacial meltwater on total mercury (THg), methylmercury (MeHg), and various Hg fractions levels in seawater, suspended particulate matter, and microplankton in Admiralty Bay, Antarctica. Stable isotope analyses of carbon and nitrogen complement Hg measurements, providing insights into food web dynamics and pollutant transfer. The average THg concentration in water samples from creeks, which may represent runoff from melting glaciers and snow, was 2.5 times higher than in sea water from Admiralty Bay. The proportion of methylmercury in total mercury varied depending on the environmental component: in water, it was 1.1 %; in SPM, 0.7 %; and in microplankton, 2.4 %. Increased microplankton biomass, which provides a larger surface area, enhanced the proportion of adsorbed HgF1, in microplankton, indicating that mercury adsorbs onto available planktonic surfaces. This research enhances our understanding of Hg cycling in Antarctic ecosystems and underscores the implications of climate change for Hg contamination, with potential effects on marine food webs and human health.