Algae that thrives on ice plays an unexpected role in glacier melting

For thousands of years, algae have lived on the surface of the ice, blooming as the snow recedes. These tiny organisms seem harmless, almost invisible, yet their presence plays a surprising role in shaping the fate of the Greenland Ice Sheet.

As the world warms, these algae may colonize larger areas, speeding up ice loss and altering the delicate balance of the Arctic.

Role of algae in ice melt

Algae on the Greenland Ice Sheet contain brown pigments. When sunlight strikes the surface, bright ice reflects much of it back into space, keeping the ice cold.

But when the ice is dark due to algal growth, it absorbs more heat and melts at a faster rate.

This process has been recognized for some time, but researchers believed that the algae’s spread was limited by the lack of nutrients in the harsh, frozen environment.

The ice desert was thought to be too barren to sustain widespread growth. That assumption has now been turned on its head.

New findings, published in Nature Communications, suggest that these algae require very few nutrients to survive.

More significantly, they can store and conserve energy, which allows them to spread more extensively than previous expectations.

If this proves correct, ice darkening could happen on a much larger scale in future, thus accelerating the melting of Greenland’s ice.

Understanding ice algae

Laura Halbach, who recently earned her Ph.D. at Aarhus University, has played a crucial role in uncovering this surprising phenomenon.

Now a postdoctoral researcher at the Max Planck Institute in Bremen, she continues her work studying Arctic ecosystems and their hidden complexities.

“My main goal with the trip to Greenland was to understand the mechanisms of the algae bloom formations,” Halbach explained.

“With new methods, I was able, as the first researcher ever, to measure the activity of single algae cells from the Greenland Ice Sheet. This led to the discovery of their ability to live off very few nutrients and to store up energy.”

These findings reshape what scientists thought they knew about microbial life on ice. What was once considered a largely lifeless landscape now appears to host a thriving and resilient ecosystem.

Powerful world of ice algae

Ice algae are single-celled organisms with an elongated, oval shape.

They appear brownish due to their pigments and can be found not just in Greenland but also in high-altitude and high-latitude ice regions worldwide.

The Alps, the Himalayas, and Alaskan glaciers all host similar algal species.

Like plants, these algae perform photosynthesis, producing oxygen and organic molecules. They rely on sunlight, water, and carbon dioxide, along with small amounts of essential nutrients like phosphorus, nitrogen, and carbon.

During spring and summer, they bloom, forming dark patches across the ice. The larger the bloom, the more heat the ice absorbs, creating a cycle where melting fuels even more algal growth.

Understanding how they function is key to predicting their long-term impact on the Arctic.

A frozen desert full of life

That perception that ice sheets are devoid of life started to change in 2020 when researchers from Aarhus University and GFZ Helmholtz Center for Geosciences in Germany began their expeditions into the Arctic.

They found that the expanses of frozen water teemed with microscopic life, including algae, bacteria, fungi, and even viruses, all coexisting and forming a complex and active ecosystem.

But this discovery came with challenges. When scientists collected ice samples, they found not just algae but entire microbial communities.

Studying algae in isolation became nearly impossible. To understand their particular role in the ecosystem, researchers needed a new approach.

A new way to study algae

Laura Halbach wanted to pinpoint exactly how ice algae functioned in their environment. But isolating them from their microbial neighbors was difficult.

Traditional methods involved scraping darkened ice and placing samples into petri dishes, where entire ecosystems would be present.

“If you melt a piece of the surface ice, you see these dark-pigmented algae. But there are many organisms in the sample, including snow-algae, other eukaryotic algae, bacteria, and fungi,” she explained.

To solve this, Halbach and her team introduced marked nutrients into the ecosystem. These nutrients contained isotopic traces detectable with a powerful machine called a mass spectrometer.

Nutrient Flow in ice algae

“You could say that we kind of labeled the food we gave them. This enabled us to see who ate what. Combined with a machine called SIMS, which is extremely precise, we were able to measure the nutrient uptake of single cells,” says Halbach.

The results were striking. The algae efficiently absorbed the small amounts of nutrients available, proving far more resourceful than scientists had expected.

“They are very efficient in taking up the limited nutrients on the ice. Furthermore, we discovered that they have the capability of storing phosphorus, which is crucial for their metabolism.”

Where does phosphorus come from?

Phosphorus is rare on the ice sheet, which raises questions about where the algae acquire it.

Some researchers suggest that it originates from local rock formations that are rich in phosphorus-bearing minerals.

As erosion grinds these rocks into dust, the wind scatters the nutrients across the ice, making them available to the algae.

Because the algae can store phosphorus, they are not entirely dependent on immediate nutrient availability. This could allow them to spread into new areas as more ice becomes exposed each year.

Expanding ice algae colonization

With climate change causing the Greenland Ice Sheet to melt earlier each year, more ice is being exposed to the Sun.

Areas that once remained buried under thick layers of snow are now vulnerable to colonization by algae.

“New ice is being exposed on Greenland every year because the snow melts earlier and earlier. There used to be a thick snow cover all year round, but now large new areas of ice are being exposed to the Sun,” Halbach noted.

“This opens up these areas for the algae to colonize, and as they can live on very limited amounts of nutrients, it might happen sooner than later.”

This shift could significantly alter how scientists predict ice loss in the Arctic. If algae spread to newly exposed ice, they will darken even more of the surface, accelerating the melting process beyond previous estimates.

Implications for climate models

Laura Halbach’s research offers crucial insights into the role of algae in ice loss. Currently, most climate models do not account for microbial life in their calculations.

This gap means that predictions about Greenland’s ice loss – and its effects on global sea levels – may be underestimating the true impact.

If algae colonization continues to expand, its contribution to ice melt will need to be factored into climate projections.

The work of Halbach and her team could help refine these models, leading to more accurate forecasts for the Arctic’s future.

The study is published in the journal Nature Communications.

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