A recent study finds that algae can store nutrients, potentially allowing them to spread across more of the ice sheet, accelerating its darkening and melting.
It’s May. The sun is up, and the heat from that distant star can finally be felt as a warm, tingling sensation on the skin.
The snow begins to melt. Flowers and plants break through the ice, gasping for light. Meanwhile, algae living on the ice sheet bloom, darkening the surface.
It has been this way for thousands of years.
But soon, this may change. Spring arrives earlier each year due to climate change, potentially allowing algae to colonize increasingly larger areas of the ice.
These algae contain brown pigments that darken the ice, reducing its ability to reflect sunlight. As a result, the ice melts faster.
This has been known by polar researchers for quite some time. But it was believed that the algae has limited capabilities of colonizing the ice, because of the lack of nutrients in this ice desert.
Until now.
New results published in Nature Communications show that algae are able to live off very few nutrients. And that they are able to store and save up energy. This makes it possible for them to colonize much more of the ice sheet than previously thought.
Laura Halbach, who recently got her Ph.D. degree at the Department of Environmental Science at Aarhus University, together with her research team, is behind the discovery. Now a postdoc at the Max Planck Institute in Bremen, she continues unraveling the mysteries of the arctic ecosystems.
“My main goal with the trip to Greenland was to understand the mechanisms of the algae bloom formations. With new methods I was able to, 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,” she says.
The life of an ice alga
Ice algae are small single-celled organisms. Elongated, brownish, and ellipse-shaped.
They thrive on ice surfaces around the world. They have been found on the Greenland ice sheet, in the Alps as well as on glaciers in the Himalayas and Alaska.
Like plants, the ice algae releases oxygen through photosynthesis and produces organic molecules. It needs sunlight, water, and CO2 as well as small amounts of phosphorus, nitrogen, and carbon to survive.
During spring and summer, the ice algae blooms creating large patches of darkened ice.
The ice sheet is teeming with life
Not that many years ago the Greenland ice sheet was thought of as a frozen desert. Desolate and almost devoid of life. But since the first researchers from Aarhus University and GFZ Helmholtz Center for Geosciences in Germany arrived in 2020, this has gradually changed.
Now we know that the ice is teeming with microbial life.
Expedition after expedition has revealed more and more of the secret life of the ice algae. One major breakthrough was the discovery that the algae is not alone. A whole ecosystem of microorganisms lives on the ice: bacteria, fungi, and even viruses.
But this made it hard to do specific studies of the algae. When researchers scrape off samples of blackened ice, the petri dishes are filled with whole ecosystems. Until now the researchers have only been able to manipulate and test hypotheses on all of the microorganisms at once. And that was what Laura Halbach set out to change.
“If you melt a piece of the surface ice, you see these dark-pigmented algae. But there are many organisms in the sample as well as snow-algae, other eukaryotic algae, bacteria, and fungi.”
“What is commonly done is to incubate the whole community. You give them a nutrient and measure the uptake in the whole community. But then it remains unclear what role the different organisms play.”
Zooming in on single cells
Because Laura Halbach was interested in understanding the role of the ice algae in the ecosystem on the ice, she couldn’t just isolate them. Instead, she fed the whole ecosystem marked nutrients. Minuscule isotopic traces that can be recognized by a machine called a mass spectrometer.
“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,” Laura Halbach explains.
The data from the machine showed that the algae effectively consumed the small amounts of nutrients available – and that they had some stored as well. Something that was completely unknown to the researchers.
“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.”
Phosphorus is very limited on the ice. Some research suggests that it comes from local rocks containing minerals with phosphorus in them. When the rocks are turned into mineral dust by erosion, it’s scattered across the ice and becomes available to the algae.
A game changer in understanding ice algae
Because the ice algae are able to store phosphorus, they can potentially colonize areas of the ice with very limited amounts of these nutrients. Thus the darkening of the ice might spread to larger areas than was previously thought possible.
“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.”
“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.”
Laura Halbach’s discoveries are not only fascinating but also important, because the knowledge of the algae’s nutrient requirements can help us to better predict their future role in the melting of the Greenland Ice Sheet. Today microbes are not yet integrated into most Earth climate models.
These new discoveries will hopefully be included in the climate models, making them more precise in predicting the melting of the ice in the years to come – and how it will impact the global climate.
Reference: “Single-cell imaging reveals efficient nutrient uptake and growth of microalgae darkening the Greenland Ice Sheet” by Laura Halbach, Katharina Kitzinger, Martin Hansen, Sten Littmann, Liane G. Benning, James A. Bradley, Martin J. Whitehouse, Malin Olofsson, Rey Mourot, Martyn Tranter, Marcel M. M. Kuypers, Lea Ellegaard-Jensen and Alexandre M. Anesio, 19 February 2025, Nature Communications.
DOI: 10.1038/s41467-025-56664-6
The study is part of the project DeepPurple which has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme. Aarhus University Research Foundation, the Max Planck Society, The Helmholtz Recruiting Initiative, and the Agence Nationale de la Recherche have also contributed.
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3 Comments
Very well written story! The author describes the essence of the research in the very first sentence. Sometimes science articles begin with, in the beginning God created the heavens and the Earth. Info overload!
And mankind builds blacktop roads and parking lots and black roofs and black solar panels all over the planet, absorbing the light energy that warms the air. They should be painted white or silver Tt4
And mankind builds blacktop roads and parking lots and black roofs and black solar panels all over the planet, absorbing the light energy that warms the air. They should be painted white or silver.