The frozen landscape of Antarctica is holding a dangerous metal. The continent is releasing higher levels of mercury into the ocean and marine ecosystem because of climate change, and the toxic metal is accumulating in the region’s wildlife, causing health problems in the food chain. Mercury has also reached the commercial fish industry, potentially risking poisoning in humans.
Mercurial matter
Mercury accumulation in Antarctica, specifically on the Antarctic Peninsula, has “doubled relative to the global shelf average and risen sharply since industrialization,” said a study published in PNAS. The increase is “driven not only by atmospheric deposition but also by climate-warming–induced ice melt and erosion that remobilize legacy mercury stored on land.” Essentially, climate change “acts as an amplifier of mercury cycling,” said study co-author Maodian Liu, an environmental scientist at Peking University in China, to Eos.
The scientists “analyzed 16 sediment cores collected from the continental shelf off the Antarctic Peninsula” and “used a variety of chemical analyses to determine the amount and sources of mercury that was deposited in the sediment over the past 200 years,” said Eos. “Nearly all the sediment cores showed a significant increase in mercury accumulation since industrialization.” And on average, “cores in the region showed a 160% increase in accumulation since industrialization, with rates accelerating particularly quickly beginning in the 1950s.”
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Mercury can be released into the environment “naturally by volcanoes and geological weathering,” said Science Alert. The continent has been “functioning as a kind of mercury ‘sink,’ locking away large amounts of pollution in its layers of ice,” which has “probably been helping reduce the amount of mercury getting into marine food chains (and our seafood).” Polar warming and ice melt are now “turning Antarctica’s cryosphere from a mercury sink into an active secondary pollution source, with important implications for future mercury risk in polar oceans and ecosystems,” said the study.
Mercury “reaches Antarctica through the atmosphere, traveling from sources such as coal plants and mining operations to settle on Antarctic ice and the Southern Ocean,” said Eos. As the metal “accumulates in sediment, it can transform into methylmercury, a more toxic form that more readily accumulates in living organisms.”
Methylmercury “enters and travels through the Antarctic food web, taken up by plankton, then krill, fish, seabirds, and marine mammals,” said Eos. The toxin can “harm animals’ neurology, behavior, growth and reproduction.” It can also get to commercial fisheries, where mercury pollution can affect human health. Now, mercury levels in “Antarctic species such as Antarctic toothfish, marlin and sharks frequently exceed previous records and food safety limits,” said Science Alert.
Antarctica is not the only place experiencing toxic mercury. In the Arctic, “permafrost thaw has begun to release trapped mercury into ecosystems,” said Eos. In the “northeastern United States, increasingly intense storms are accelerating erosion and mobilizing nutrients and metals, including mercury.” While reducing emissions is the best way to reduce the level of ice melt and mercury leaking, said Liu to Eos, “environmental mercury burdens” are “unlikely to decline immediately in step with emission reductions.”
