Science News

Sea ice responsible for rising mercury in Antarctic fish, birds

Researchers say Antarctic sea ice is encouraging the accumulation of methylmercury, a more toxic form of mercury, in birds and fish.

Scientists with the U.S. Geological Survey in Wisconsin, Lawrence Livermore National Laboratory and the University of Melbourne, analyzed different types of mercury, as well as communities of microorganisms, in ice and water samples collected from Antarctica.

The research showed that bacteria in sea ice helps convert the mercury into its more toxic form, which accumulated in local food chains. When humans consume larger fish, they absorb methylmercury. An accumulation of methylmercury in humans can cause brain development issues and other health maladies.

“These results are the first to identify a particular genus of bacteria, Nitrospina, as capable of producing methylmercury in Antarctic ice,” John Moreau, University of Melbourne geomicrobiologist, said in a news release.

Mercury is leeched into the environment from natural processes like volcanoes and wildfires, as well as human activities like mining and burning fossil fuels.

The latest research, detailed in the journal Nature, is one of the first to examine one of the natural processes that turns mercury into a more toxic form.

“The presence of these potential mercury-methylating bacteria raises an interesting question,” Moreau said. “Could they also play a role in forming the methylmercury observed in the oceans worldwide?”

Moreau and his colleagues believe future studies must look at how both mercury accumulation in the ocean and atmosphere will affect humans and other animals as the climate gets warmer.

“We need to understand more about marine mercury pollution,” said Moreau. “Particularly in a warming climate and when depleted fish stocks means more seafood companies are looking south.”