The Ice is Alive: Uncovering the Vanishing World of Glacial Microbes

Bathed in the golden glow of the midnight sun, the frozen expanse of the Svalbard archipelago stretches out in endless silence around Arwyn Edwards. To the naked eye, these wind-scoured glaciers appear to be sterile deserts. Yet, immediately beneath the crunch of Edwards’ boots, the ice teems with an invisible and thriving biosphere, lush with bacteria, fungi, and viruses. Scientists have estimated that the glaciers and ice sheets around the globe could contain as many as 10²⁹ cells.¹

“The biomass that’s stored within the planet’s glacial ice is broadly comparable to the amount of biomass that you have in the soils of all the rainforests on earth,” said Edwards, a glacial microbiologist at Aberystwyth University.

In the early 20^th century, a team of scientists on an expedition to Antarctica analyzed glacial ice and falling snow on the frozen continent and cultured the meltwater on nutrient plates.² To their surprise, they found various types of bacteria and yeast in the samples, calling into question the assumption that Earth’s cryosphere was devoid of life. However, concerns about the sterility of the samples and methods used to grow the microbes cast doubt on these findings.

More than half a century later, a slew of studies provided further evidence of the existence of extremophiles in glacial environments around the world. Whether inside the deep ice cores of the Antarctic ice sheet or in the icy surface layers of Alpine glaciers, specialized microbes are capable of not only surviving in these harsh conditions but utilizing the meager resources to their advantage. Scientists have been teasing apart the biology of these extremophiles to uncover their unique adaptations, understand historical climate patterns, study biogeographic cycles, and even discover new drugs.

But now, just as the cryosphere’s biome comes into focus, it is collapsing. As rising temperatures drive the rapid retreat of glaciers worldwide, the unique ecosystems embedded within the ice are vanishing. This physical destruction has triggered a desperate scientific race to catalog these specialized microbial communities and salvage their genetic secrets before the ice turns to water, flushing an entire ecosystem into extinction.³

“Glaciers are more than frozen water. They are ecosystems. The ice is alive,” said Tom Battin, a microbial ecologist at the Swiss Federal Technology Institute of Lausanne. “We are in a race against time to understand their unique biodiversity.”

Cryoconite Forms an Oasis on the Glacial Surface

Edwards’ fascination with the microscopic world of glaciers began serendipitously. In 2006, a piece of out-of-commission laboratory equipment left him unable to run the experiments he had planned. With his primary work stalled, he had no choice but to tag along on his supervisor’s field trip to the ice of Svalbard.

“I was mainly supposed to help carry things in the field, but along the way, to keep my PhD supervisor happy, I agreed to do some actual science,” Edwards said. That accidental detour launched a career that has since taken him on 46 expeditions across the Arctic, Antarctic, the mountain ranges of Europe and Scandinavia, and Greenland.

To the uninitiated, the glaciers Edwards studies might appear as monolithic slabs of frozen water, but they are defined by distinct, active layers. The most dynamic of these is the surface, where windblown dust mixes with microorganisms to form a dark, granular sediment known as cryoconite.⁴ Because this aggregate is darker than the surrounding white ice, it absorbs more solar radiation, melting the ice beneath it. This melting creates water-filled depressions called cryoconite holes that pockmark vast areas of the ice sheet. Cryoconite holes are far from simple puddles; they are oases of life in a polar desert.

“Cryoconite forms a microhabitat that can host maybe 2,000 species of microbes and can have photosynthesis rates comparable to temperate soils,” Edwards said. “All of this is sitting at 0.1ºC in a very austere environment.”

However, studying them presents a logistical nightmare: By the time samples travel from a remote ice cap to a university laboratory, the delicate microbial community may have already become altered or degraded. To bridge this gap, Edwards pioneered a radical shift in fieldwork by bringing the lab to the ice. In 2017, he established a portable genomic sequencing setup—nanopore sequencing—compact enough to fit inside a standard rucksack.⁵ Using this “lab-in-a-backpack,” scientists can extract and sequence DNA anywhere, generating complex metagenomic data within just 36 hours of collection.

“Since then, it’s become commonplace for people to do nanopore sequencing in an ever-growing set of weird environments,” Edwards said.

This real-time analysis revealed that cryoconite holes harbor region-specific microbiomes, each uniquely adapted to the distinct conditions of their local cryosphere.⁶ In an analysis of the changes to global glacial biodiversity published in 2019, scientists found that as glaciers recede, specialized microbial groups residing in them decline, to be replaced by generalists.⁷

While the specific biological signatures in cryoconite holes vary from the Arctic to the Alps, the functional roles remain consistent. Dominating this microscopic landscape are Proteobacteria, Bacteroidetes, and, most crucially, Cyanobacteria.⁸

These blue-green algae serve as ecosystem engineers. Through photosynthesis, cyanobacteria generate between 75 to 95 percent of the available carbon in the cryoconite pools, fueling the food web for fungi, archaea, viruses, and even certain invertebrates that live there too.⁹

Dark Pigments Protect Ice Microbes But Hasten Glacier Melting

Survival in cryoconite holes requires ingenuity. To endure the freeze-thaw cycles and intense solar glare, cyanobacteria secrete a cocktail of extracellular polymeric substances—a sticky matrix of proteins, lipids, and polysaccharides. This “slime” acts as a multipurpose shield: a natural cryoprotectant to keep cell membranes from shattering in the cold, while also trapping UV-protective compounds to prevent radiation damage.¹⁰

These survival strategies, however, have consequences far beyond the microscopic pool of water. The dark pigments the algae produce to protect their DNA from UV radiation combined with the dense mineral dust on the ice surface creates cryoconite, which darkens the glacier’s pristine surface, reducing the reflectivity of the ice.

Limnologist Birgit Sattler focuses on the study and protection of glacier ecosystems at the University of Innsbruck. Sattler and her team have demonstrated that cryoconite dramatically lowers the ice’s albedo, or reflectivity. The difference is staggering; while pristine ice might reflect about 60 percent of incoming sunlight, areas with cryoconite reflect only 10–20 percent.¹¹ This substantial decrease in albedo means solar energy is transferred directly into the ice surface, significantly accelerating melt rates. This creates a positive feedback loop: The resulting meltwater provides the microbes with the liquid habitat they need to grow, and their increased growth further amplifies the melting effect. Microbes don’t just endure the ice; they actively transform it.

“This is visible all over the world,” Sattler said. “The first findings were in Greenland, but we also see it in the Alps.”

Protecting glaciers while also thinking about the life within them proves challenging. Efforts to safeguard vulnerable ice caps sometimes involve large-scale geoengineering solutions, such as covering the ice with huge white polypropylene sheets intended to boost reflectivity and slow melting. Sattler characterized the effort to cover glaciers as a compromise. She noted that shielding the ice blocks the sunlight essential for the surface bacteria, thus fundamentally disrupting the entire microbial food web that those organisms sustain.

Edwards agreed. “The danger is that if we go ahead with these schemes incautiously, we will save frozen water. We won’t be saving living ice,” he said.

Sattler’s research also helped to highlight the environmental cost of this intervention. The sheets often shed microplastic pollution onto the ice, introducing a new layer of contamination directly into the fragile microbial ecosystem.

“A glacier is like a mirror to society,” Sattler said. “Anything that we release in our civilized world—such as pesticides, microplastics, heavy metals—they might be out of our mind, but they get deposited on the glacier ice. They get stored and eventually are released to end up in front of our doors.”

To monitor this emerging problem and bridge the gap between research and public awareness, Sattler leads citizen science programs across glaciers in the Austrian Alps, such as the Tyrolean glacier. For over 20 years, she has integrated school children directly into the research process, taking them onto the ice. The students collect their own samples and participate in the data observation efforts to document the spread of microplastics and other airborne pollutants. By empowering the next generation to observe the life within the ice, the work ensures that even as the glacier retreats, the understanding of its unique, vanishing biology is preserved for future conservation efforts.

Microbes Shape the Chemistry of Glacier-Fed Streams

The microbial activity on the glacier’s surface is only the beginning of the story; that life eventually flows into glacier-fed streams (GFS)—the uniquely cold, turbulent, and nutrient-poor arteries leading away from the ice that serve as vital sources for rivers.¹²

Despite their global importance, “the microbial life in the deepest ocean was better understood than the microbial life in the streams that drain the roof of our planet,” Battin said.

To remedy this profound lack of data, Battin established the Vanishing Glaciers Project in 2018, launching a global, systematic effort to understand these vulnerable ecosystems before they disappear. Battin’s team spent five years on a massive undertaking, collecting samples from 170 GFS spanning major mountain ranges from the European Alps to the Himalayas and the Andes. “Many of them have never seen a human being. It was really wild,” Battin said.

The streams’ microbes form slimy biofilms on the submerged rocks, acting as the gut of the waterway.¹³ GFS microbes are the first stop for all carbon and nutrients washing out of the glacier, efficiently processing the material and controlling the water’s chemistry.

Battin and his team used sensors and fiber-optic cables to measure the stream’s vital signs, like the water’s oxygen concentration, to gauge microbial respiration. This labor-intensive work, combined with advanced metagenomic analysis, revealed that GFS microbes possess a core set of survival traits for metabolizing varied substances across the globe. More remarkably, the scientists found that almost half of the GFS bacteria profiled were endemic to their region—some even unique to a specific mountain range, creating specialized microbial lineages found nowhere else on Earth.¹²

Battin’s team combined this massive genomic database with climate models to predict how future glacier shrinkage might affect GFS microbiomes.¹⁴ They speculated that the resulting warmer streams will cause a functional shift toward ‘greening’—increased growth of photosynthetic microbes—accompanied by a loss of clades that have adapted to environmental harshness. The specialized, endemic organisms will likely be outcompeted by common, generalist species better suited to the new, warmer conditions.

The irreversible loss of this ancient microbial biosphere demands more than just scientific cataloging; it necessitates global policy intervention to slow the melting that is physically destroying the habitat. However, at current rates of global warming, irreversible loss of many glaciers is imminent. Considering this dire future, scientists are taking immediate action to conserve the life within glaciers. A team led by Battin is working to establish a microbial biobank in Switzerland to archive the cryosphere’s vanishing species.

“The idea is to build a biobank that allows us to actively do research on these microbes and harness their power,” Battin said. “For instance, looking for cold adapted enzymes and novel antibiotics.”

Edwards hopes that by making the best effort to store the unique biodiversity of glaciers, the scientific community can secure a vital legacy for future generations.