Antarctic Sea Ice Houses Bacteria Capable of Coverting Mercury to Neurotoxin

A new study has confirmed that the Antarctic Sea Ice is housing a certain type of bacteria capable of converting Mercury to its more toxic form, which could in turn contaminate the marine environment, including fishes and birds.

The study, published in the journal Nature Microbiology, revealed that a certain genus of bacteria called Nitrospina has the genetic ability to convert mercury to a potent neurotoxin known as methylmercury.

Methylmercury is a very poisonous form of mercury that can travel through the brain and cause developmental and physical problems in fetuses, infants and children when ingested. This neurotoxin could build up in the food web through the process called biomagnifications. Small contaminated fish is eaten by a larger fish, which will then be eaten by a larger fish. As the process continues, methylmercury can accumulate at harmful levels for human consumption.

For the study, the researchers collected samples of the Antarctic sea ice. The sea ice is then analyzed for different types of Mercury at the US Geological Survey in Wisconsin (USA), while the DNA and proteins from the sea ice were analyzed at the University of Melbourne (AUS) and Lawrence Livermore National Lab (USA).

With the discovery of the Nitrospina in the Antarctic sea ice, the researchers want to determine if the mercury-methylating bacteria also plays a role in the forming of methylmercury observed in the oceans worldwide.

"Mercury has a long lifecycle in the atmosphere, up to a year," said co-author Dr Robyn Schofield, in a statement. "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."

Mercury is a heavy metal pollutant produced during human activities, including gold smelting and burning fossil fuels. It can also be naturally released in the environment through volcanic eruptions and re-released from vegetation during bushfires.

The toxic metal is being deposited into the seas all year long but increases during the Antarctic spring, when the returning sunlight causes reactions that boost the amount of mercury falling onto sea ice and the ocean.