Glaciers provide fertile ground for film productions. In “The Day After Tomorrow” the Earth is suddenly plunged into an ice age; “Snowpiercer” presents a futuristic vision of the world, where the remaining humans live their lives on a train darting across the frozen Earth; and the blood-chilling horror “The Thing” deals with an extraterrestrial "thing", dug out of the ice in Antarctica.

There is also “The Iceman”, which tells the story of Ötzi – a Neolithic man, found by tourists in 1991 in the Ötztal Alps, where he had melted out of the ice. Glacial periods have occurred repeatedly throughout the Earth’s history, so disaster films based on the idea of a sudden onset of another ice age are not entirely improbable. How about potential dangers lurking in glaciers and permafrost? Ice has been part of the global landscape for at least a few million years. Is it, therefore, a repository of potentially dangerous organisms and substances, which science is not yet aware of? Does climate warming mean we are soon going to find out? If the melting ice could yield a Neolithic traveller, complete with Lyme disease he had been suffering from  and a number of microscopic plant parasites in the folds of his clothing, we cannot rule out the possibility of more frozen surprises of the sort. After all, glaciers may easily serve as freezers for dormant microbial cysts, seeds, bacteria, fungi or viruses.

Surprising bacteria

According to scientists, the number of active microorganism cells melting out of glaciers every single year may be as high as 10¹⁷ or even 10²¹. The question remains if these cells are potential pathogens and may pose a threat to human society. What makes it all the more valid is the relatively young age of the Homo sapiens, which means that human immune system may not yet have come into contact with biological material hundreds of thousands years old. Scientists have managed, for example, to reactivate bacteria (found in permafrost cores extracted in Yakutia) which lay dormant in the frozen ground for 70 000 years. Some of the bacteria showed signs of antibiotic resistance, which means that microorganisms released by melting glaciers may swell the ranks of bacteria resistant to the available antibiotic medications. Polish scientists who looked into antibiotic resistance mechanisms and genes on the glaciers of the Caucasus, Greenland and Svalbard found out that the glaciers they studied were not only repositories of resistance, but also places where the resistance could be passed from one bacterium to another. If, in other words, a tourist or a scientist (or any vertebrate, for that matter) leaves a drug-resistant bacterium on a glacier, that resistance may spread onto other bacteria found in the area, amplifying the risk they might pose to public health.

At the turn of the 19^th and 20^th centuries, over a million deer in northern Russia died of anthrax infection, out of which more than 13 000 ended up buried. In 2016, the melting ground began to release the bacteria, causing infections among the inhabitants of the Yamalo-Nenets Autonomous Okrug. And although we might dismiss the case as too distant in space and time to cause much concern, there are others that hit closer to home. Each year, mountaineers and tourists leave tons of waste, including human waste, on the world’s glaciers, like those surrounding Alaska’s Mount Denali. For the time being, the waste is frozen solid along with a number of nasty biological surprises it likely contains. The estimates suggest, however, that about 70 years from now the material will be released into the ecosystems below the glacier, which may lead to an ecological disaster and is a serious threat to visiting tourists.

Microscopic trouble, or viruses

Viruses play a vital role in glaciers and permafrost. By infecting bacteria, viruses make their cells disintegrate and thus contribute to carbon exchange within a given ecosystem. A few years ago, global headlines rang with the news of a scientific discovery that threw a new light on the process. What the scientists found in the permafrost of Siberia was a virus capable of infecting protozoa. The news wouldn’t be all that exciting had it not been for the fact that the said virus had been frozen for the previous 30 000 years! The same is true of more modern viruses, like those found in reindeer guano from 700 years ago. Or like bird flu viruses (still capable of infecting living organisms, including humans) found in an ice lake in Siberia and in frozen penguin guano in Antarctica. What is more, less than a year ago scientists investigating ice cores from the Himalayas found 22 groups of viruses, 15 of which had not been previously known to science. And although discovering new viral groups is not particularly surprising in the world teeming with undescribed life, it may be important from the point of view of pathogens, which the human body has not yet encountered.

Glacier mushroom picking

Glaciers are also home to microscopic, mostly single-cell fungi, related to the mushrooms common in more familiar environments. Some are examples of harmless environmental fungi, which decompose organic matter accumulating on glacier surface. Some other may potentially be dangerous. Like the fungi which, after being frozen for 150 000 years, were isolated from ice samples collected in Greenland and Antarctica and turned out to belong to yeast-like fungi capable of infecting humans. Aureobasidium pullulans, for example, is one such fungus found in many glaciers. It occurs commonly in modern ecosystems and often grows on other plants. There is evidence, however, that prolonged exposure to the fungus may cause lung and skin diseases. A recent paper on the “resurrection of inactive microbes” (full title: Resurrection of inactive microbes and resistome present in the natural frozen world: Reality or myth?), published in Science of the Total Environment, draws attention to the fact that older strains and diverse forms of the same fungus may be potentially dangerous not only to humans, but – most of all – to animals and plants living in the glaciers’ vicinity.

Is that all?

Latest research indicates that, when it comes to potential sources of danger, there is more to glaciers and permafrost than biotic elements, such as living organisms or viruses. Microscopic organisms inhabiting glaciers appear to be quite efficient at intercepting pollutants and storing them for extended periods of time. It turns out that the concentrations of artificial radionuclides (which is to say, those left after nuclear tests or nuclear power plant failures) found on the glaciers of Spitsbergen, the Alps or the Caucasus exceed the amounts detected in land ecosystems (in mosses, lichen and peat). In glaciers, the concentrations of radioactive caesium (¹³⁷Cs) or americium (²⁴¹Am), whose decay is harmful to living organisms, are greater than those in the soils of Chernobyl! Some scientists suggest that the fast rate of glacier melting, especially in the Alps, may cause a rapid inflow of concentrated radioactive material into the ecosystems located below the melting glaciers. Fortunately, for now this is no more than a hypothesis, rooted just as firmly in science as in fiction. The fact remains, however, that – apart from artificial radionuclides – glaciers are believed to store heavy metals (accumulating on glacier surface since the Industrial Revolution), black carbon (formed by the incomplete burning of fossil fuels) or even pesticides. We can only imagine what other scary stuff lies hidden inside these gorgeous icy giants.

Author: Dr. Krzysztof Zawierucha

Translation: Barbara Jóźwiak

Bibliografia

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