Supercold Algae Play Vital Role in Arctic Food Web

Tiny Diatoms Undergird the Food Chain Crucial for Indigenous Cultures

Assorted diatoms as seen through an optical microscope. These specimens were living between crystals of annual sea ice in McMurdo Sound, Antarctica. Prof. Gordon T. Taylor, Stony Brook University/Wikipedia

New research reveals that Arctic diatoms—microscopic algae—can actively move and survive in sea ice at temperatures as low as −15° C (5° F). This groundbreaking discovery means that these tiny organisms play a far more dynamic role in the Arctic food chain than previously thought and serve as a vital and active food source for marine life during the long, dark Arctic winter.

This discovery not only reshapes scientists’ understanding of life in extreme environments but also underscores the delicate and interconnected balance that sustains both wildlife and human life in the Arctic.

The Arctic food chain is uniquely dependent on sea ice algae. In the past, scientists believed these algae were mostly dormant and trapped within the ice, providing a limited food source.

However, research from Stanford University, published on September 9, 2025, in Proceedings of the National Academy of Sciences, shows diatoms are not only surviving but also actively gliding through icy channels using actin filaments. This gliding movement persists at −15 °C (5 °F), the lowest temperature ever recorded for motility in a eukaryotic cell.

This movement allows them to continue providing a crucial energy source during a time of year when other food sources are scarce. Diatoms are consumed by zooplankton like copepods and krill, which are then eaten by Arctic cod and other small fish. These fish, in turn, are the primary food for marine mammals such as seals, walruses, and whales. At the top of this chain are polar bears, which rely on seals for survival. Essentially, the ability of these microscopic algae to remain active and available as a food source during the coldest months is a matter of life and death for the Arctic’s largest predators.

Mechanism and Observations

The researchers, led by Manu Prakash, an associate professor of bioengineering at Stanford, collected ice cores from 12 stations throughout the Chukchi Sea during a 45-day Arctic expedition in summer 2023, aboard the research vessel Sikuliaq. Using custom microscopes onboard, they imaged inside the ice and observed the diatoms moving. They then created a winter environment by lowering the temperature of a “special sub-zero microscope” below freezing and by putting thin layers of frozen freshwater over very cold saltwater, mimicking natural micro-channels that form when sea ice expels salt.

Even under these subzero conditions, the diatoms glided using a combination of mucus secretion (polymeric material) and molecular motor machinery (including actin filaments). Temperate diatoms, by contrast, do not show the same ability to glide within ice substrates at such low temperatures.

Regarding the prevalence of algae in the Arctic food chain, Prakash noted that the team’s underwater drone revealed that, while “the Arctic is white on top … underneath it’s green—absolute pitch green because of the presence of algae.”

Inuit fishermen in Uummannaq, Greenland, prepare longlines on dinghies to catch Greenland halibut and other Arctic fish, which are ultimately dependent on diatoms and other phytoplankton. Creative Commons

Impact on Human Beings

The health of the Arctic food chain directly affects Indigenous communities that depend on subsistence hunting.

For example, the Inuit and other Arctic peoples hunt marine mammals like seals and whales, whose populations are sustained by the productivity of the lower food chain. The resilience of diatoms in extreme cold ensures the continued health of the ecosystem that has supported these cultures for millennia.