Microbial diversity: glaciers teem with life

The rivers that flow at the top of glaciers are complex ecosystems, little known until recently. A team of scientists led by EPFL carried out an unprecedented study, examining in depth the microbiome of these waterways. With the help of mountain guides and porters, scientists spent more than five years collecting and analyzing samples from 170 glacier-fed streams in New Zealand, the Himalayas, the Russian Caucasus, in the Tien Shan and Pamir Mountains, in the European Alps, in Scandinavia, in Greenland, in Alaska, in the Rwenzori Mountains in Uganda and in the Ecuadorian Andes and Chilean.

The research was led by Tom Battin, full professor of environmental sciences and director of the RIVER laboratory at EPFL, as part of the Vanishing Glaciers project funded by the NOMIS Foundation. The main conclusions of the scientists were recently published in “Nature” and “Nature Microbiology” on January 1 and 2, 2025, EPFL communicates on January 8.

These freshwater ecosystems, the most extreme in the world, all have roughly the same characteristics: temperatures near freezing, low nutrient concentrations, almost no sunlight in winter and strong UV radiation in summer. “Given the extreme conditions that prevail in these waterways, we expected that microbial diversity would be low overall and that it would vary little from one mountain range to another,” explains Leïla Ezzat, post -doctoral student and main author of the article published in “Nature”. “But our analyzes proved otherwise: microbial biodiversity and biogeography are remarkable in glacier-fed streams around the world.”

The scientists used their sampling to develop the first global atlas of microbes present in glacier-fed waterways. They discovered a unique microbiome in these environments that clearly differs from other cryospheric systems, such as permafrost and mountain lakes. Additionally, almost half of bacteria are endemic to a given mountain range.

This is particularly the case in New Zealand and Ecuador, regions already known for their wide variety of endemic plants and animals. Scientists attribute this phenomenon to the geographic isolation of mountains, similar to that of islands, and to natural selection, which is particularly strong in these extreme environments. The Nature article also provides insight into the strategies that allow bacteria to evolve in one of the most extreme ecosystems on the planet.

The article published in “Nature Microbiology” presents the analysis of thousands of genomes of bacteria, archaea, fungi, algae and viruses living in glacier-fed streams. This research has revealed the complexity of this microbiome and the many potential relationships between organisms it contains.

“It is fascinating to see the wide range of adaptive strategies that microorganisms have developed to survive in this extreme environment,” says Grégoire Michoud, lead author of the paper. “For example, these microorganisms have evolved to metabolize a variety of substances (organic carbon, solar energy, minerals and probably even gases), allowing them to derive energy from many different and fluctuating sources.”

2025 has been named by the United Nations as the International Year of Glacier Conservation. Preserving our glaciers also means protecting glacier-fed waterways and their microbiome: an urgent task to accomplish given the speed of melting ice.

“Having spent the last few years hiking the planet’s mountain peaks, I can say that we are clearly losing a unique microbiome as glaciers disappear,” says Tom Battin. The researcher thus calls for the creation of a biobank to safeguard not only this microbiome, but also other microbiomes that are disappearing for future generations of scientists. These samples could also be used with next-generation biotechnology. He hopes that such a “vault” will see the light of day in Valais. “Given the skills of the Alpine and Polar Environment Research Center (ALPOLE) at EPFL in Valais, it seems logical to install a biobank there,” says Tom Battin.