Hundreds of thousands of viruses in the oceans

According to the latest statistics, the oceans contain nearly 200,000 different viral populations.

Marine viruses were found from the surface up to 4,000 m depth and from the North Pole to the South Pole.

Although most are safe for humans, they can infect marine life, including whales and crustaceans.

And scientists are just beginning to understand how these microorganisms play a role in life and the chemistry of the seas.

Researchers at Ohio State University have compiled a global map of marine viruses from seawater samples collected from nearly 80 sites around the world. Their number of viruses is almost 12 times higher than previous estimates.

They were surprised to find that the viruses only fell in five groups, depending on their location and depth.

"When we examined the genes of the viruses in each of these communities, we found evidence of genetic adaptation to different areas of the ocean," said researcher Ann Gregory, now of KU Leuven in Belgium.

The second surprise was that the Arctic Ocean contained many types of viruses. It had been thought that the hot spots of microbial diversity would be located at the equator.

What are the viruses doing in the oceans?

The oceans of the world are full of viruses, but we are at the limit of our understanding of how they affect the health and functioning of the oceans.

Among the previous discoveries, there are the "giant" marine viruses, which can infect green algae.

A liter of seawater usually contains billions of viruses, the vast majority of which have not yet been identified. In the last set of data, 90% of the populations could not be classified in a known group.

A better understanding of ocean viruses is important because of their influence on other marine microbes, including bacteria and fungi.

Viruses have an impact on all other tiny marine organisms, such as plankton, that produce more than half of the oxygen we breathe and absorb carbon dioxide from the atmosphere.

"Without microbes, the Earth, its oceans and even our human body are stopping," said Matthew Sullivan of Ohio State University. "Our laboratory is finally helping researchers to" see "the hidden viruses that infect these microbes."

The study is reported in the journal Cell. Most of his data comes from the Tara Oceans expedition (2009-2013) using the 36 m aluminum hull research schooner, Tara.

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