Rapidly melting glaciers release staggering payload of unknown bacteria: ScienceAlert

Rapidly melting glaciers are releasing staggering amounts of bacteria into rivers and streams, which could transform frozen ecosystems, scientists warn.

In a study of glacial runoff from 10 sites across the northern hemisphere, researchers estimated that continued global warming over the next 80 years could release hundreds of thousands of tons of bacteria into environments downstream of the retreat. glaciers.

“We think of glaciers as a huge store of frozen water, but the key lesson from this research is that they are also ecosystems in their own right,” said microbiologist and study author Arwyn Edwards of the University. of Aberystwyth in the UK. Told the BBC.

Glaciers are masses of ice crawling very slowly out to sea, carving out mountain valleys as they go. Yet there’s more to the outflows than frozen water, with minerals, gases and organic matter trapped on a one-way slip that could take tens of thousands to millions of years To end.

Studying the contents of glaciers it’s like opening the door to another era in history. The microbes buried inside could be a rich source of useful new compounds, such as antibiotics. However, the researchers behind this new study say melting glaciers are releasing tons and tons of bacteria faster than scientists can catalog them.

Led by glacier hydrologist Ian Stevens of Aarhus University in Denmark, the team sampled surface meltwater from ten glaciers in the northern hemisphere: in the European Alps, Greenland, Svalbard and in the confines of the Canadian Arctic.

Finding an average of tens of thousands of microbes in every milliliter of water, they estimate that more than a hundred thousand tons of bacteria could be expelled into glacial meltwater over the next 80 years, not including glaciers in the Asian region. from the Himalayan Hindu Kush.

This equates to 650,000 tonnes of carbon released per year into rivers, lakes, fjords and oceans in the Northern Hemisphere, although this depends on how fast glaciers are melting and how fast we reduce emissions.

Under a “middle of the road” emissions scenario – which would see global temperatures rise another 2-3C – masses of bacteria in meltwater are expected to peak in decades before declining or disappearing altogether as glaciers retreat, the researchers found.

“The number of microbes released is highly dependent on how quickly the glaciers are melting, and therefore how much we continue to warm the planet. But the mass of microbes released is vast even with moderate warming,” Edwards said. said.

A group of scientists standing on a glacier in Greenland.
Researchers are taking samples from the western edge of the Greenland Ice Sheet. (Arwyn Edwards/Tristram Irvine-Fynn, University of Aberystwyth)

Earlier this year, scientists realized that Arctic ice is already thinning faster than expected. Other research suggests that some glaciers have already past a tipping point where meltwater slows to a trickle as glacial runoff steadily decreases.

Microbes in meltwater can fertilize downstream ecosystems, but these may be sensitive environments or catchments used by communities that rely on glacial runoff as a source of water.

The researchers didn’t study individual strains of bacteria, only estimate their combined biomass, so they couldn’t identify any species that might pose a threat to human health – or whether the microbes were active, dormant, damaged or dead.

“The risk is probably very low, but it requires careful assessment,” Edwards said. Told Stefan Messenger at the BBC.

Without further studies, we also don’t know how the sudden influx of microbes could contribute to further environmental changes. The researchers expect this could have a profound effect on the productivity and biodiversity of microbial communities, as well as on biogeochemical cycles.

Additionally, bacteria and algae found in icy environments typically contain pigments to protect themselves from the sun’s harmful rays. But these pigments, by absorbing solar energy, could add to the warming already accelerating glacial ice loss.

While more research is needed to assess the downstream effects of microbial-laden glacier meltwater, these warnings should not be taken lightly. Human thirst for water and ceaseless industrial activity have reshaped the global water cycle in a way that we are only just beginning to understand.

“Over the coming decades, the predicted ‘water peak’ of Earth’s mountain glaciers means that we need to improve our understanding of the state and fate of glacier surface ecosystems,” said glaciologist and study author Tristram Irvine-Fynn at Aberystwyth University.

“With a better understanding of this image, we could better predict the effects of climate change on glacial surfaces and watershed biogeochemistry.

The study was published in Earth & Environment Communications.

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