Antarctic sea ice acts as a massive, overlooked storage unit for climate-regulating microbes, according to research published in Nature Communications. Scientists from Stellenbosch University, alongside collaborators from the United Kingdom and Italy, discovered that sea ice contains DMSP concentrations up to 38 times higher than the surrounding Southern Ocean water during the austral winter. This compound helps microorganisms survive extreme, subzero temperatures and serves as a precursor to climate-cooling gases like dimethylsulfide.
Why does Antarctic sea ice matter for global climate?
The Southern Ocean plays a disproportionate role in Earth’s climate system, absorbing nearly half of the atmospheric carbon taken up by the world’s oceans, according to the study. During the austral winter, sea ice expands to form a ring around Antarctica covering roughly 20 million square kilometers. Dr. Mayi Buthelezi, a marine microbiologist at Stellenbosch University and the study’s lead author, notes that this ice is not merely a frozen barrier but a “dynamic reservoir and transformation hub.” By harboring microbial communities that cycle sulfur, the ice influences the production of gases that help regulate global temperatures.
The sea-ice ecosystem is one of the most extreme environments on Earth, with internal temperatures remaining between -1°C and -20°C throughout the winter months.
How do microbes survive in extreme cold?
Microorganisms trapped in sea ice utilize DMSP as a survival mechanism, according to Dr. Buthelezi. When environmental conditions become too stressful—such as the hypersaline and freezing conditions of sea ice—microbes synthesize or import DMSP to act as a buffer. This process is not energetically expensive, making it a viable strategy for survival when growth resources are scarce. The study’s metagenomic data confirms an enrichment of genes responsible for DMSP synthesis within the ice, contrasting with the open seawater where microbes primarily focus on DMSP degradation for carbon and sulfur.
What is the significance of the SCALE expedition data?
Data collected during the Southern Ocean Seasonal Experiment (SCALE) in July 2022 provides a rare look at the Antarctic winter. Accessing the region is notoriously difficult due to extreme winds and the massive expansion of sea ice, which has historically led to an overrepresentation of summer data in climate models. Prof. Thulani Makhalanyane, senior author of the study, emphasizes that the expansion of data infrastructures and bioinformatics is allowing researchers to fill these geographic gaps. By analyzing these winter samples, scientists are now able to better understand how microbial life differs in iron-limited marine ecosystems compared to more temperate waters.
Comparison: Sea Ice vs. Open Seawater
| Feature | Sea Ice | Open Seawater |
|---|---|---|
| DMSP Concentration | Up to 38x higher | Lower |
| Primary Gene Activity | DMSP Synthesis | DMSP Degradation |
Frequently Asked Questions
What is DMSP?
DMSP (dimethylsulfoniopropionate) is an organic sulfur compound produced by marine microbes. It protects organisms from environmental stress and acts as a source of carbon and sulfur.
Why are climate-cooling gases important?
The degradation of DMSP produces dimethylsulfide and methanethiol. These gases are released into the atmosphere and play a critical role in cooling the planet.
How were the samples collected?
Researchers collected the samples during the SCALE austral winter expedition in July 2022, operating aboard the South African polar research vessel, the SA Agulhas II.
Do you want to stay updated on the latest marine research and polar science? Subscribe to our monthly newsletter for deep dives into how our oceans are changing.
Worth a look