Toxic levels of methylmercury found in Antarctic sea ice, fossil fuels to blame

A new study from the University of Melbourne in Australia has reported methylmercury found in Antarctic sea ice are at toxic levels, with researchers citing the continued use of fossil fuels as the primary cause of the problem.

“Mercury has a long lifecycle in the atmosphere, up to a year,” says Robyn Schofield of the School of Earth Sciences at the University of Melbourne and co-author of the study. “This means that mercury released through fossil fuel burning from countries over 3000 km away goes up in the atmosphere and ends up in Antarctica.”

The most toxic form of the heavy metal pollutant mercury, methylmercury is a neurotoxic compound that once having entered the body moves quickly into the brain and central nervous system, severely affecting neural development in fetuses and damaging brain, heart, kidney, lung and immune functioning in adults.

The toxic build-up in a region’s ecosystem starts with elemental mercury, produced in trace amounts by the combustion of fossil fuels, which is acted upon by aquatic bacteria found in oceans, lakes, rivers and even soils and transformed into the more poisonous methylmercury. The toxin can then move up the food chain through a process called biomagnification, as plankton containing methylmercury get eaten by small fish who are then consumed by larger fish, increasing the concentration levels of methylmercury along the way.

Researchers aboard the icebreaker Aurora Australis collected samples of Antarctic sea ice, snow and sea water to test for mercury levels and concluded that the bacteria Nitrospina was the most likely source of methylmercury found in the sea ice. “We need to understand more about marine mercury pollution,” said study co-author John Moreau of the University of Melbourne. “Particularly in a warming climate and when depleted fish stocks means more seafood companies are looking south.”

At the other end of the globe, high concentration levels of methylmercury in Arctic marine life has been blamed on global warming and melting sea ice in Arctic and sub-Arctic areas. When sea ice melts it changes salinity levels in the ocean, which in turn affects the availability of organic matter -including methylmercury-producing bacteria- for ingestion by marine plankton.

Researchers studying the projected environmental impact of the Muskrat Falls hydroelectric dam in Labrador measured methylmercury levels in Lake Melville, downstream from the dam, still under construction and found toxic concentrations of the poison.

“We found more methylmercury in the water than our modeling could explain,” says Amina Schartup of the Harvard John A. Paulson School of Engineering and Applied Science. “All of the methylmercury from the rivers feeding into Lake Melville and from the sediment at the bottom of the lake couldn’t account for the levels in the water. There was something else going on here.”

The researchers argue that reservoir flooding for the new dam will drastically increase mercury levels and likely have significant effects on Aboriginal communities which rely upon the region’s aquatic ecosystem for food. “This system is incredibly efficient at accumulating methylmercury,” says Schartup.

The $7.7 billion Muskrat Falls project aiming to bring power to Newfoundland and Labrador and tie the province to the North American energy grid is facing controversy on a number of fronts over construction costs, delays and potential environmental and health impacts.

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