New research has found methylmercury – a potent neurotoxin – in sea ice in the Southern Ocean.Published today in the journal Nature Microbiology, the results are the first to show that sea-ice bacteria can change mercury into methylmercury, a more toxic form that can contaminate the marine environment, including fish and birds.If ingested, methylmercury can travel to the brain, causing developmental and physical problems in foetuses, infants and children.