Scientists have warned that huge amounts of bacteria could be released as the world’s glaciers melt due to climate change.
Potentially harmful pathogens are among the thousands of microbes that can leak into rivers and lakes.
Researchers at Aberystwyth University said their study highlighted the need to act quickly to curb global warming.
They studied meltwater from eight glaciers in Europe and North America and two sites in Greenland.
Glaciers are huge bodies of slow-moving ice that have formed over hundreds or thousands of years. As the planet warms, they are melting at an alarming rate, causing sea levels to rise.
The Aberystwyth University team estimated that the situation could lead to more than 100,000 tons of microbes, such as bacteria, being released into the environment over the next 80 years – a number comparable to all the cells in every human body on Earth.
Microbiologist Dr Arwyn Edwards said the study clearly showed for the first time the “massive scale” of surface microorganisms trapped in Earth’s glaciers.
“The number of microbes released depends very much on how fast the glaciers melt, and therefore how much we continue to warm the planet,” he said.
The team’s calculations are based on a “moderate” warming scenario, as developed by the IPCC, an international panel of climate experts.
This would cause global temperatures to rise by an average of 2C to 3C by 2100.
As the flow of microbes into rivers, lakes, fjords and seas increases, there could be “significant” impacts on water quality, Dr Edwards explains.
But this would be followed within decades by turning off the microbe tap as the glaciers disappear completely.
He said: “There are 200,000 watersheds worldwide that are fed by glacial meltwater and some of these are highly sensitive environments that are poorly developed in terms of organic carbon and nutrients.
“In others, there is a lot of economic activity and billions of people whose livelihoods depend on the water that eventually comes out of those glaciers.
“We think of glaciers as a huge store of frozen water, but the most important lesson from this research is that they are ecosystems in their own right.”
Thousands of different microorganisms grow on or are stored in glaciers, he said, some of which could be harmful to humans.
“The risk is probably very small, but it requires careful assessment.”
Glaciologist Dr Tristram Irvine-Fynn said more research was needed: “In the coming decades, the predicted ‘peak water’ of Earth’s mountain glaciers means we need to improve our understanding of the state and fate of[these]ecosystems.
“With a better understanding of that picture, we can better predict the effects of climate change on glacial surfaces and watershed biogeochemistry.”
The findings of the Aberystwyth academics are published this month in the journal Nature Communications Earth & Environment.