Over the past two centuries, Antarctica has accumulated significant amounts of mercury pollution, despite efforts to preserve the continent’s largely untouched environment.
Mercury occurs naturally through volcanic activity and the weathering of rocks. However, human activities such as fossil fuel combustion and mining have greatly increased mercury levels in the environment.
Antarctica’s Ice Has Trapped Mercury Pollution
Antarctica has acted as a mercury sink, trapping substantial amounts of this pollution within its layers of ice. This process has likely helped limit the amount of mercury entering marine food webs and seafood consumed by humans.
However, the industries responsible for increasing mercury pollution also emit greenhouse gases, which contribute to global warming and the accelerated melting of Antarctic ice.
As Antarctica’s ice continues to melt, it is also releasing the accumulated “legacy” mercury into the surrounding ocean.
A research team led by environmental scientist Chengzhen Zhou of Peking University in China has published a study in Proceedings of the National Academy of Sciences examining the issue.
By analyzing sediment cores from the Antarctic Peninsula, the fastest-melting part of the continent, the researchers identified a worrying trend. Despite its remote location and distance from major industrial sources of mercury, the Antarctic Peninsula shelf is accumulating mercury at roughly twice the global average rate.
The study also found that mercury accumulation in the region has increased by about 160% since industrialization began in the mid-19th century.
The Atmosphere–Ocean Loop Carries Mercury to Antarctica
One of the main ways mercury reaches Antarctica from distant regions is through the atmosphere. It can be absorbed by seawater and later released back into the air, creating what scientists call the “atmosphere–ocean loop.”
However, researchers found that part of the increase in Antarctic mercury is also coming from within the continent itself. As glaciers melt and the land erodes, a process known as the “atmosphere–glacier–land–ocean loop” is activated, releasing mercury that had been trapped in the ice.
According to Zhou and his colleagues, the interaction between these two cycles has increased ice-melt-driven mercury release from land by 550% and air–sea mercury exchange by 350%.
The researchers warn that climate warming is transforming Antarctica’s historical mercury reservoir into an active secondary source of pollution, potentially increasing the risks associated with mercury contamination in polar environments.
The World Health Organization (WHO) classifies mercury among the 10 chemicals posing the greatest public health concerns, as exposure to even relatively low concentrations can be harmful.
A previous study using data from 2012 also discovered bacteria in Antarctic sea ice capable of transforming mercury into methylmercury, a highly toxic form that can accumulate in marine organisms.
This conversion makes the latest findings particularly worrying. The researchers caution that faster mercury accumulation and cycling in Antarctica could pose growing risks to the region’s marine and terrestrial ecosystems.
Methylmercury Threatens the Southern Ocean Food Web
The Southern Ocean food web, which extends from diatoms and krill to fish and larger predators, is particularly vulnerable to methylmercury contamination. Recent studies indicate that mercury concentrations in Antarctic species, including Antarctic toothfish, marlin, and sharks, are increasingly exceeding earlier measurements and established food-safety limits.
The potential consequences, however, may extend far beyond Antarctic waters.
The amount of mercury transported from the Antarctic Peninsula into the open ocean by ocean currents has increased by 400%, raising concerns that this pollution could reach ecosystems far beyond Antarctica.
The researchers warn that if other marginal seas around the Southern Ocean have experienced levels of post-industrial mercury accumulation similar to those recorded along the Antarctic Peninsula, the resulting contamination could pose an even greater threat to marine ecosystems and fisheries.
Read the original article on: sciencealert
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