A global survey finds that the Arctic Ocean is a hot spot for viruses

Arctic waters turn out to be teeming with some of the world’s smallest entities — viruses.

Water samples taken during a three-year expedition around the world’s oceans identified around 200,000 virus species, roughly 12 times the number found in a previous smaller survey. And 42 percent of those viruses were found exclusively in the Arctic, researchers report April 25 in Cell.

The results come from the Tara Oceans global oceanographic research expedition. From 2009 to 2013, researchers dropped tanks off of an aluminum sailboat called Tara to collect 145 water samples from dozens of sites worldwide, at water depths from 0 to 4,000 meters. Scientists collected everything ranging in size from fish eggs down to viruses. Filtering isolated the viruses, which were then genetically compared.

The researchers identified 195,728 virus species parsed into five global regions that are home to distinct viral communities. The most diversity was found in shallow, temperate and tropical waters, followed closely by Arctic waters.

Almost all of the viruses were bacteriophages, which attack bacteria — not people.      

“So you can swim in the ocean and not worry about it,” says Ahmed Zayed, a microbiologist at Ohio State University in Columbus.

Bacteriophages and other viruses are credited with killing roughly 20 percent of bacteria in the ocean every day. That process stops carbon in the bacteria from passing up the food chain, and instead releases the carbon back into the ocean for other microorganisms — some of which also consume carbon dioxide. These microbes eventually produce a form of carbon that can’t be recycled and stays stored in the ocean. 

Viruses may serve an important role in counteracting human-induced climate change by indirectly stashing away carbon in this way, though viruses have rarely been included in climate simulations. Having the global map of virus locations could help scientists know where carbon fallout occurs and increase the accuracy of climate simulations.

But the study gives only a limited view of viruses at play. “There’s still swaths of the ocean that haven’t been looked at,” such as the Western Pacific, says Curtis Suttle, an environmental virologist at the University of British Colombia in Vancouver who wasn’t involved in the study.

And because microbiologists can only isolate and identify viral species with DNA, viruses with RNA were excluded from the new analysis, despite being thought to make up half of the ocean’s virus diversity. “So we’re still really only scratching the surface of what’s there,” Suttle says.