Frozen and alive: Algae glide inside Arctic sea ice in subzero cold

You wouldn’t expect anything to be moving around inside a chunk of Arctic sea ice. At most, maybe a frozen microbe or two stuck in place for centuries. But that idea just got shattered.

Tiny single-celled algae called diatoms have been found not only alive in Arctic ice – but gliding around as if they were skating under the microscope.

And they’re doing it in conditions colder than almost any life has ever been observed moving in. These aren’t just tough survivors. They’re active, fast, and full of surprises.

Arctic algae defy freezing limits

Diatoms are known for their glass-like outer walls. You’ll find them floating in oceans, lakes, and even puddles. In the Arctic, researchers have long seen them trapped in ice, lined up like specks of dirt in ice cores.

The assumption was they were dormant – alive, maybe, but inactive. Turns out, that assumption was way off.

Researchers discovered that these Arctic diatoms were gliding through ice channels at temperatures as low as 5°F. That’s the coldest temperature ever recorded for a complex cell to move. And it’s not just a twitch or shiver – they’re really cruising.

Ice cores reveal hidden life

The discovery comes from a team of scientists who spent 45 days aboard the research ship Sikuliaq in the summer of 2023. They traveled through the Chukchi Sea near Alaska, collecting ice cores from 12 different stations. Along the way, they dodged sea ice and spotted polar bears.

Back in the lab, they recreated Arctic conditions using petri dishes with frozen freshwater and cold saltwater underneath. They carved tiny channels in the ice using strands of their own hair to mimic natural ice structures.

Using special microscopes designed to work below freezing, they watched the diatoms move. Instead of flailing or flapping, the diatoms slid forward smoothly. To track their motion, the researchers added fluorescent beads to gel-like material, creating glowing trails like footprints in sand.

Algae glide without limbs

The movement looks effortless, but there’s serious biological machinery behind it. The diatoms move by gliding – pulling themselves forward using a kind of sticky mucus and internal motors.

“There’s a polymer, kind of like snail mucus, that they secrete that adheres to the surface, like a rope with an anchor,” said Qing Zhang, the study’s lead author from Stanford University. “And then they pull on that ‘rope’ and that gives them the force to move forward.”

That rope-pulling system uses actin and myosin – the same molecules that power human muscle. But these algae are doing it in subzero temperatures. Understanding how this system keeps working in such cold conditions is now a major focus of the team.

The Arctic diatoms didn’t just move – they outpaced their warmer cousins. When the scientists compared them with temperate diatoms moving on glass, the Arctic ones were faster. That suggests they’ve evolved a serious edge to survive the deep freeze.

A hidden world under the ice

This isn’t just a cool biological trick. These diatoms could be a key part of the Arctic food web. They feed tiny animals, which feed bigger ones, and so on up the chain – including fish, seals, and polar bears.

“The Arctic is white on top but underneath, it’s green – absolute pitch green because of the presence of algae,” said senior author Manu Prakash. “In some sense, it makes you realize this is not just a tiny little thing, this is a significant portion of the food chain and controls what’s happening under ice.”

Knowing these diatoms are active in freezing conditions changes how we understand life in polar environments. They could be helping to move nutrients through the ecosystem, even in the dead of winter. Their mucus trails might even aid the formation of new ice, similar to how a pearl forms around a grain of sand.

Urgency in Arctic discoveries

This discovery is exciting, but it’s also happening under pressure. “Many of my colleagues are telling me, in the next 25 to 30 years, there will be no Arctic. When ecosystems are lost, we lose knowledge about entire branches in our tree of life,” said Prakash.

He also pointed to major cuts in funding. Projections suggest that the National Science Foundation’s polar research budget could drop by 70 percent. Such a reduction would mean fewer expeditions, fewer discoveries, and fewer chances to understand the rapidly changing Arctic before it is too late.

“I feel a sense of urgency in many of these systems, because, at the end of the day, the infrastructure and capacity to be able to operate is critical for discovery,” Prakash said.

The full study was published in the journal Proceedings of the National Academy of Sciences.

Image Credit: Prakash Lab

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