According to a paper by scientists from EPFL and Charles University published today in Nature Geoscience.Streams fed by glaciers are entering a process of deep change. This conclusion is based on trips made by participants of the Disappearing Glaciers project to the world’s main mountain ranges.

Microbial life will thrive in mountain streams as glaciers continue to retreat. This was reported by a team of scientists from EPFL and the Faculty of Natural Sciences of Charles University in Prague in their recent study. Their observations are based on samples collected from 154 glacier streams around the world as part of the Disappearing Glaciers project led by EPFL.

Streams fed by glaciers in summer are turbid, turbulent streams. Large amounts of glacial meltwater break down rocks and sediments, allowing little light to reach the riverbed, while freezing temperatures and snow at other times of the year provide little opportunity for a rich microbiome to develop.

However, as glaciers shrink due to global warming, the volume of water coming from the glaciers also decreases. This means streams become warmer, calmer and cleaner, giving algae and other microorganisms a chance to become redundant and contribute more to local carbon and nutrient cycles.

“We are witnessing a process of profound change at the microbiome level in these ecosystems, nothing short of a ‘green transition’ due to increased primary production,” says Tom Battin, a tenured professor at EPFL’s River Ecosystems Laboratory (RIVER).

They then looked at changes in both along a very broad stream gradient fed by glaciers of varying sizes.

“Glacier-fed ecosystems are often limited in carbon and nutrients, especially phosphorus,” explains Tyler Kohler, former RIVER postdoctoral researcher and lead author of the paper.

“As glaciers shrink and demand for phosphorus from algae and other microorganisms increases, phosphorus may become more limited in high-elevation streams.” Thus, phosphorus, a fundamental building block for life, will become even more scarce in downstream ecosystems, with as yet unknown impacts on food webs.

These results are confirmed by a published document. Royal Society Open Science By scientists from the Vanishing Glaciers project in August 2023. In this study, the authors analyzed the microbiome of a small glacier-fed river in Uganda’s Ruwenzori Mountains, where the “green transition” is already in an advanced stage. Here, too, the composition of nutrients and enzymes was significantly different and there was a lot of algae.

“What’s happening at the Ruwenzori glacier gives us an idea of ​​what glacier-fed Swiss streams will look like in 30 or 50 years,” says Battin. One consequence of this change is that glacier-fed streams will play a greater role in biogeochemical cycles such as CO flux because they contain more microbial life.₂.

The RIVER team plans to continue this research. They are conducting microbial biodiversity censuses in glacier-fed streams and using different genomic information to investigate how diverse microorganisms can survive in one of the most extreme freshwater ecosystems on Earth.

Lead author Tyler Kohler, currently a research assistant at the Department of Ecology at the Faculty of Natural Sciences of Charles University in Prague, was responsible for sample collection during the expeditions, laboratory analysis and writing of the paper. Tyler is currently the leader of Charles University’s PRIMUS project titled: A Green New World: Unraveling Patterns of Microbial Community Assembly in Endangered Glacier-Fed Streams.

In this project, Tyler’s team continues this research by focusing on how algal communities (specifically diatoms) in glacier-fed waterways are changing with climate change.