Southern Ocean, Antarctica – Scientists have discovered that Antarctic sea ice contains a dense and active microbial system that plays a major role in climate-related chemical processes during the harsh winter months.

A study led by South African researchers found that winter sea ice around Antarctica hosts large populations of microbes capable of producing and breaking down dimethylsulfoniopropionate (DMSP), a sulfur-containing compound that helps organisms survive extreme environmental stress.

Measurements showed that DMSP concentrations in sea ice can be up to 38 times higher than in surrounding seawater. At peak extent, Antarctic sea ice covers around 20 million km2 and forms a vast ring encircling the continent, stretching up to 1,900 km wide.

DMSP serves as a protective compound for microbes and breaks down into dimethylsulfide (DMS) and methanethiol (MeSH), both linked to climate-cooling gas production. Researchers say this makes sea ice a biologically active environment rather than an inert frozen mass.

Genetic analysis revealed widespread microbial pathways involved in DMSP cycling, including genes linked to algae and previously unidentified bacterial producers. These findings suggest that microbial communities in sea ice are highly adapted to survive and function under extreme winter conditions.

The study also shows that sea ice microbes use DMSP both as a stress-response mechanism and as a source of carbon and sulfur, while microbes in seawater mainly use it for nutrient breakdown.

Researchers from Stellenbosch University, working with international partners, say the Southern Ocean marginal ice zone is a key global hotspot for sulfur cycling, where microbial activity contributes to the production of climate-cooling gases.

Overall, the findings highlight the important role of microbial life in Antarctic sea ice in shaping chemical processes that influence Earth’s climate system.

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