If you were to slice a chunk of Arctic sea ice and peer at it under a microscope, you probably wouldn’t expect much. Frozen water, trapped sediment, perhaps a few still-living microbes locked in stasis. But look closer.
Along delicate veins within the ice, single-celled algae called diatoms are skating. The researchers identified several Arctic diatoms, primarily from the genus Navicula, using microscopy and DNA barcoding.
“You can see the diatoms actually gliding, like they are skating on the ice,” said Qing Zhang, a postdoctoral scholar at Stanford University and lead author of a new study published in Proceedings of the National Academy of Sciences. “The diatoms are as active as we can imagine until temperatures drop all the way down to –15°C, which is super surprising”.
This is the lowest temperature at which movement has ever been recorded in a eukaryotic cell—the same cells like those in humans, trees, and fungi.
This discovery opens a window into a hidden, mobile world beneath the Arctic’s frozen surface, but also raises urgent questions about how life is changing as the ice above it disappears.
Microscopic Skaters of the Chukchi Sea
The revelation came from a 45-day summer expedition through the Chukchi Sea, a region of the Arctic Ocean nestled between Alaska and Russia. Aboard the research vessel Sikuliaq, scientists from the Prakash and Arrigo labs at Stanford collected ice cores from 12 locations.
Some of those cores looked like they were streaked with dirt. But under custom sub-zero microscopes—some built from scratch by the research team—those streaks came to life.
Inside narrow, hair-thin channels in the ice, diatoms were gliding. Not twitching. Not wriggling. Gliding smoothly along surfaces that they should have been frozen into.
“There’s a polymer, kind of like snail mucus, that they secrete that adheres to the surface, like a rope with an anchor,” Zhang explained. “And then they pull on that ‘rope’ and that gives them the force to move forward.”
That ‘rope’, researchers discovered, is made of mucilage—a slippery, protein-rich secretion. Embedded in it are the same molecular machines that power human muscles: actin and myosin. Somehow, those motors still operate at –15°C.
Even more astonishing: while their relatives living in temperate climate zones stall out at around –1°C, the Arctic diatoms move nearly ten times faster on ice at freezing temperatures.
Life in Motion, Against All Odds
Why would such small organisms glide through such a hostile place?
The answer lies in light and salt.
Arctic sea ice forms a porous matrix riddled with microscopic brine channels. These narrow veins allow diatoms to inhabit precise microzones where light filters through and salinity is just right. During long polar nights and cold seasons, staying mobile could be a matter of survival.
“[Diatoms] are believed to select specific depths within the ice core that offer optimal light, nutrients, and salinity,” the team wrote in their study. Without movement, they might miss those ephemeral windows of opportunity.
The researchers found that only Arctic diatoms can move through actual ice. Temperate diatoms (species from warmer waters) lost all movement on frozen surfaces. They failed to adhere to the ice and drifted only through currents or collisions.
On both glass and ice, Arctic species showed not just faster movement, but a completely different resilience to cold. When Zhang and her team measured the force needed to detach them from icy surfaces, Arctic diatoms held fast. Temperate ones peeled off immediately.
This unique adhesion, the researchers believe, may involve specialized ice-binding proteins. These molecules are also used by some cold-dwelling bacteria and fish to stick to or resist freezing.
The Physics of Skating Cells
By adding tiny fluorescent beads to the water and watching how they moved, the team mapped the forces diatoms generate as they move. Those beads acted like footprints in the snow, tracing invisible trails beneath the cells.
They also built a thermodynamic model that simulates how internal forces, such as those from the myosin motors, balance against external drags—like the sticky resistance of mucilage and the fluid surrounding the diatom.
What emerged was a portrait of energy efficiency: ice diatoms have evolved both lower internal energy demands and external materials (like their mucilage) that change less with temperature than those of temperate species.
A Dynamic Engine Beneath the Ice
Arctic diatoms are super important in the polar food web. They form the base of an ecosystem that sustains everything from krill to seals to polar bears. If they’re not just surviving in ice—but moving, navigating, and reshaping their surroundings—that changes how we understand the flow of nutrients and energy in one of Earth’s most extreme environments.
“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, a Stanford bioengineer who has spent years developing tools to study life in difficult environments. “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”.
Some researchers believe diatom mobility could even influence ice formation and melting. Their secretions might serve as nuclei for new ice growth.
The discovery arrives at a critical moment. The Arctic is warming faster than any other place on Earth. Many projections suggest the region could be ice-free in summer within the next 25 to 30 years.
“Many of my colleagues are telling me, in the next 25 to 30 years, there will be no Arctic,” Prakash said. “When ecosystems are lost, we lose knowledge about entire branches in our tree of life”.
And that loss could happen just as scientists are beginning to uncover how those ecosystems work. The specialized microscopes and field experiments used in this study depend on long-standing support from organizations like the National Science Foundation. But those programs are facing steep budget cuts—up to 70 percent for polar research, by some estimates.
Without infrastructure like the Sikuliaq, or time to develop and deploy tools like Zhang’s sub-zero microscope, entire microbial worlds could remain uncharted.
