Beneath the icy expanse of the Southern Ocean lies a complex and largely unexplored world of microscopic life that quietly shapes Earth’s climate. Credit: Shutterstock

A sweeping genetic survey of Antarctic waters reveals a hidden microbial world with untold influence on Earth’s climate.

The ocean surrounding Antarctica may look remote and empty, but it quietly helps regulate the planet’s climate. This region, known as the Southern Ocean, absorbs enormous amounts of heat and carbon dioxide from the atmosphere. Much of that work is carried out by plankton, microscopic organisms that drift with ocean currents yet play a central role in Earth’s carbon balance.

A new study published March 9 in Nature Communications offers one of the most detailed looks yet at the genetic makeup of these organisms. By mapping their DNA, scientists are beginning to uncover how this hidden ecosystem functions and why it matters for the future of the climate.

The research is based on nearly ten years of work led by biogeochemist Nicolas Cassar of Duke University’s Nicholas School of the Environment, alongside an international team. Their goal was to better understand how microbial life in one of the harshest environments on Earth influences global systems.

“The Southern Ocean is massive and plays a disproportionate role in terms of heat and carbon uptake from the atmosphere,” Cassar said. “We wanted to better understand microbial diversity in the region, because those microbes affect the carbon cycle in different ways.”

The Hidden Power of Phytoplankton

Among these organisms are phytoplankton, microscopic marine life that carries out about half of all photosynthesis on Earth. By doing so, they remove large amounts of carbon dioxide from the atmosphere.

To study them, researchers examined DNA from water samples collected across the Southern Ocean during a three-month expedition in late 2016 and early 2017. After sequencing the genetic material, they compared it with existing gene catalogs and grouped samples based on shared traits, including adaptations to cold environments.

The findings revealed a major gap in current knowledge. At least one-third of the identified genes do not appear in existing marine gene catalogs, highlighting how much remains unknown about ocean microbes.

“When we looked at the databases, a huge portion of these genes just wasn’t there. That’s a sign we’re charting largely uncharacterized genetic territory,” he said.

Distinct Ecosystems Beneath the Surface

The study also found that microbial communities are unevenly distributed across the Southern Ocean. Instead, they form distinct ecosystems shaped by ocean circulation patterns. Some thrive in cold surface waters, while others are found at greater depths.

According to Cassar, the next step is to explore this newly uncovered genetic diversity in more detail to better understand how it both influences and responds to climate change.

“Microbes regulate much of the ocean’s chemistry,” he said. “To understand how the Southern Ocean will influence future climate, we need to understand the genes that control those microbial processes.”

Reference: “Water mass specific genes dominate the Southern Ocean microbiome” by Emile Faure, Jolann Pommellec, Cyril Noel, Alexandre Cormier, Lisa-Marie Delpech, A. Murat Eren, Antonio Fernandez-Guerra, Chiara Vanni, Marion Fourquez, Marie-Noëlle Houssais, Ulysse Guyet, Corinne Da Silva, Frederick Gavory, Aude Perdereau, Karine Labadie, Patrick Wincker, Julie Poulain, Christel Hassler, Yajuan Lin, Nicolas Cassar and Loïs Maignien, 9 March 2026, Nature Communications.
DOI: 10.1038/s41467-026-69584-w

Funding: The Antarctic Circumnavigation Expedition was funded by the Swiss Polar Institute and Ferring Pharmaceuticals.

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