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Some of the world's smallest entities, viruses, are overflowing with water in Arctic waters.
Water samples taken during a three-year expedition into the world's oceans have identified about 200,000 virus species, about 12 times more than in a previous smaller survey. And 42% of these viruses were found exclusively in the Arctic, researchers report April 25 Cell.
The findings come from Tara Oceans' global oceanographic research expedition. From 2009 to 2013, researchers dumped tanks on an aluminum sailboat called Tara collect 145 water samples from dozens of sites around the world, at depths ranging from 0 to 4,000 meters. The scientists gathered everything from fish eggs to viruses. The filtering isolated the viruses, which were then compared genetically.
The researchers identified 195,728 virus species analyzed in five regions of the world with distinct viral communities. The greatest diversity was found in shallow, temperate and tropical waters, followed closely by arctic waters.
Almost all viruses were bacteriophages, which attacked bacteria – not humans.
"So you can swim in the ocean without worrying," says Ahmed Zayed, a microbiologist at Ohio State University in Columbus.
Bacteriophages and other viruses are responsible for the death of about 20% of bacteria in the ocean each day. This process prevents the carbon contained in bacteria from moving up the food chain, and releases it back into the ocean to turn it into microorganisms, some of which also consume carbon dioxide. These microbes eventually produce a form of carbon that can not be recycled and stays stored in the ocean.
Viruses can play an important role in the fight against man-made climate change by indirectly blocking carbon in this way, although viruses have rarely been included in climate simulations. Having the global map of virus locations could help scientists know where carbon spill occurs and increase the accuracy of climate simulations.
But the study only gives a limited view of the viruses at stake. "There are still parts of the ocean that have not been examined," like the Western Pacific, says Curtis Suttle, an environmental virologist. at the University of British Columbia in Vancouver, which did not participate in the study.
And since microbiologists can only isolate and identify viral species with DNA, RNA viruses have been excluded from the new analysis, although they are supposed to account for half of the viral diversity of the ocean. "So we're just really scratching the surface of what's there," says Suttle.
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