Sea-ice bacteria generate a potent neurotoxin.
We’ve all heard warnings about mercury in fish. It builds up in food webs through a process called biomagnification, whereby a large fish eats a small, contaminated fish, and then an even larger fish eats that one, with the toxic mercury becoming more concentrated at each step.
Mercury can be transformed into an even more potent neurotoxin, called methylmercury, which contaminates marine environments and accumulates in food webs much in the same way as mercury. If ingested during pregnancy, methylmercury can be absorbed by the fetus, and it takes a heavy toll on the developing brain.
According to new study published in the journal Nature Microbiology, marine bacteria living in Antarctic sea ice can facilitate the transformation from mercury to methylmercury.
A team of researchers collected samples of Antarctic sea ice during a two-month expedition. The samples were analyzed for different forms of mercury, as well as DNA and proteins belonging to sea ice microbes.
The team discovered that a bacterium present in the sea ice, called Nitrospina, possesses the genetic ability to convert mercury into its more toxic form.
Mercury gets released into the environment through volcanic eruptions and re-released from vegetation during bushfires. Another major source is human activity, such as gold smelting and burning of fossil fuels.
Senior study author John Moreau of the University of Melbourne tells ABC News: “What we typically think of as pristine Antarctica actually has the potential to convert mercury pollution into a form that's toxic to the marine food web.”
With a warming climate, Moreau can’t help but wonder: “Would increased methylmercury be available to the ocean food web if that ice melted or melted faster?”
The findings underscore the imminent need to eliminate mercury pollution from the natural environment.
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