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More and more glaciers are melting as the Earth heats up, posing a multitude of threats to humanity. From rising sea levels to increased coastal erosion, the record speed at which the world's ice sheets are melting has the potential to disrupt societies globally.
Now scientists from Aberystwyth University warn that hundreds of thousands of tonnes of microbes could leak into lakes and rivers as the world's glaciers melt due to climate change, according to an institutional press release.
"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 Aberystwyth University, UK.
An entire ecosystem trapped inside
Glaciers have an entire ecosystem trapped inside. As snow fell year after year in the coldest places on Earth, it was slowly compressed to form ice, trapping microorganisms and preserving them in a dormant state. As the Earth's temperature continues to rise, the ice has started to melt, releasing ancient microbes that are being flushed down into the lakes and rivers.
In the study, researchers collected surface meltwater from eight sites across Europe, North America, and two sites on the Greenland ice cap. They found tens of thousands of microbes in each milliliter of water.
The team estimated that the situation could result in more than a hundred thousand tonnes of bacteria being expelled into glacial meltwaters over the next 80 years, not including the glaciers in the Himalaya Hindu Kush region of Asia.
The figure is equivalent to 650,000 tonnes of carbon being released into our environment per year, depending on how fast the glaciers melt and whether humans can curb climate change.
The team's calculations are based on a "moderate" warming scenario, where the global temperature is expected to rise between two degrees Celsius and three degrees Celsius on average by 2100. If carbon emissions are cut, slowing global heating and ice melting, the mass of microbes released would be reduced by about a third.
"The number of microbes released depends closely on how quickly the glaciers melt and, therefore, how much we continue to warm the planet. But the mass of microbes released is vast even with moderate warming," Edwards said.
A doomsday pathogen melting out of the glaciers
The first virus to be isolated and reactivated from permafrost was in 2014. It was from a genus of giant viruses called Pithovirus. The virus was viable in a 30,000-year-old ice core taken from the Siberian permafrost.
Since then, researchers have isolated various microbes, with some having pathogenic potential. However, the likelihood of these microorganisms becoming the next pandemic is thought to be relatively low.
"The risk is probably very small, but it requires careful assessment," said Edward in a statement.
How could these microbes transform the ecosystem?
Researchers note that some microbes could have positive impacts, such as fertilizing the ecosystems they come into contact with. At the same time, others could also be the source of new antibiotics, a somewhat hopeful expectation.
Further studies are needed to understand how tonnes of microbes released would affect our ecosystem.
"Over the coming decades, the forecast' peak water' from Earth's mountain glaciers means we need to improve our understanding of the state and fate of ecosystems on the surface of glaciers," says glaciologist and study author Tristram Irvine-Fynn at Aberystwyth University.
The study was published in Communications Earth & Environment.
Study abstract:
Melting glacier ice surfaces host active microbial communities that enhance glacial melt, contribute to biogeochemical cycling, and nourish downstream ecosystems; but these communities remain poorly characterised. Over the coming decades, the forecast ‘peak melt’ of Earth’s glaciers necessitates an improvement in understanding the state and fate of supraglacial ecosystems to better predict the effects of climate change upon glacial surfaces and catchment biogeochemistry. Here we show a regionally consistent mean microbial abundance of 104?cells?mL?1 in surface meltwaters from eight glaciers across Europe and North America, and two sites in western Greenland. Microbial abundance is correlated with suspended sediment concentration, but not with ice surface hydraulic properties. We forecast that release of these microbes from surfaces under a medium carbon emission scenario (RCP 4.5) will deliver 2.9???1022?cells?yr?1, equivalent to 0.65 million tonnes yr?1 of cellular carbon, to downstream ecosystems over the next ~80 years.
