mysterious “giant” viruses found in rare lake

Quebec researchers have discovered so-called “giant” viruses under the ice, in a rare lake. These viruses, which infect microscopic algae, could teach us more about the extreme aquatic ecosystems of the region plagued by climate change.

A surprising discovery in an “epi-platform” lake

The notion of a giant virus is obviously not new, although very recent – ​​dating from the early 2000s. These viruses have a size greater than 0.2 microns as well as a genome containing more than 300,000 base pairs. In 2018, for example, researchers surveyed the forest near Harvard University (United States) over 1,200 hectares and unearthed no less than 16 unknown giant viruses. However, each discovery of this kind can potentially be of interest to virologists.

In a study published in the journal Applied and Environmental Microbiology On August 25, 2022, biologists from Laval University (Quebec) analyzed water samples and discovered, using DNA sequencing, a wide variety of microorganisms, including giant viruses of the family Megaviricetes. These are characterized in particular by their size which can exceed that of certain bacteria.

The discovery was made in the Arctic Ocean, 800 km from the North Pole, in Lake Milne Fiord. The latter is a so-called “epi-platform” lake, that is to say where from fresh water rests on salt sea water (more dense). The fact is that the water is covered with a layer of ice preventing the formation of waves at lake level or the mixing of the two types of water under the effect of the wind. According to scientists, this is a very rare phenomenon.

Credits: Laval University / Applied and Environmental Microbiology

An ecosystem threatened by climate change

Quebec biologists indicate that giant viruses infected microscopic algae having elected residence between the two types of water, at the limit of salt water. Yet scientists have yet to figure out how this is possible. New research will therefore have to be carried out to find out more about this mysterious body of water. In addition, the researchers say they have started a real race against time because, according to them, climate change represents a threat. Indeed, the ice is likely to melt while the latter – acting as a dam – allows the separation and the stability of both types of water and therefore of this whole strange ecosystem.

Epi-platform lakes were once more common in the Arctic but are now very rare, according to the study’s lead researcher, Mary Thaler. In addition, the study of viruses would be essential in the understanding of polar aquatic ecosystemsof the region. It must be said that in these areas remain micro-organisms whose genetic characteristics are unknown, or even totally unknown.

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