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Researchers sail on the Tara ship during their expedition to the Cercle Polaire in 2013. (Credit: A. Deniaud Garcia / Tara Ocean Foundation)
The oceans are teeming with viruses. An international team of researchers has studied the world's oceans, pole pole, since it surveyed the waters in search of micro-organisms and discovered nearly 200 000.
Although viruses are mainly thought of in terms of disease, in the oceans, viruses and other marine microbes have a disproportionate impact on marine ecosystems. Their role is so important that researchers say that microorganisms can help predict how oceans will respond to climate change.
"This new understanding of viruses … could help scientists better understand the behavior of the oceans under the pressures of climate change," said Ahmed Zayed, a graduate student in microbiology at Ohio State University in Columbus. declaration.
Carbon controller
The oceans absorb about half of the carbon dioxide that man emits into the atmosphere. But microbes, which account for about 60 percent of the ocean's biomass, largely control the fate of this carbon, says Matthew Sullivan, Ohio State's ecologist for the virus, who spearheaded the new research. Viruses, for example, kill between 20% and 40% of ocean bacteria each day, releasing carbon and other nutrients from it, creating food for marine life.
"We need to understand the viruses so we do not short-circuit this carbon pump and perhaps even exploit them to our advantage as we seek bold and innovative solutions to help us overcome climate change," Sullivan said. .
This prompted Sullivan and his team to undertake a vast survey of the world's oceans after a series of expeditions. During the first two trips, between 2009 and 2011, the team collected approximately 100 seawater samples from around the world and discovered approximately 1,500 viruses. At the time, the results published in 2016 tripled the number of known viral populations in the oceans. But the most recent investigation of an expedition into the Arctic eliminates this number of people.
In the new study, researchers report the results of the Tara Oceans Polar Circle expedition. In 2013, researchers circled more than 1,500 miles of the Arctic Ocean, collecting seawater from different depths at 20 sites. After filtering the water and separating the viruses, the scientists extracted the DNA and sequenced the genetic material. They added this new batch of samples to their previous collection of the first two trips, for a total of 145 samples from the world's oceans.
Arctic Hotspot
When the researchers analyzed the new collection of viruses, they identified nearly 200,000 viral populations. The discovery "expand[s] Ann Gregory, a graduate student at Sullivan's lab who led the effort, said in a statement.
Scientists have used the new catalog to draw the world's first map of the diversity of viruses in the ocean. The map revealed that the diversity of viruses is surprisingly high in the Arctic, researchers said April 25 in the newspaper Cell. Scientists were expecting a low diversity of viruses in the Arctic because large organisms had less biodiversity, both on land and at sea, as well as at the poles.
"We were surprised to see the Arctic as a hotspot for biodiversity, which is particularly important as these waters are among the fastest changing waters on the planet due to climate change," he said. said Sullivan.
The discovery suggests that "the Arctic could be an unrecognized" cradle "of viral biodiversity beyond the tropics and highlights the importance of these highly climate-impacted Arctic regions for global biodiversity," said Zayed.
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