Thousands of Previously Undescribed Viruses Found By Huge Ocean Survey

The first global survey of marine RNA viruses has discovered thousands of new viruses, some of which play a central role in locking away carbon at the bottom of the sea. From a report: Between 2009 and 2012, researchers aboard a ship called Tara collected seawater samples from all the world's oceans. Guillermo Dominguez-Huerta at the Ohio State University and his colleagues had previously looked at hundreds of thousands of DNA viruses in these samples and found they were concentrated in five major ecological zones, with some of the greatest diversity in the Arctic Ocean. But this only told half of the story. The ocean is also filled with viruses that have genomes made of a different genetic material called RNA, which cells use to direct protein synthesis. Analysing DNA viruses was relatively easy using existing methods, but the researchers had to come up with improved techniques to distinguish viral RNA from the surfeit of RNA produced by the other organisms swimming in each sample. Now, Dominguez-Huerta and his colleagues have published the biggest-ever survey of RNA viruses in the ocean using the samples from Tara. The researchers identified more than 5000 types of RNA viruses in the sea, almost all of which were new to science. "It has expanded our view of how much diversity there is," says Curtis Suttle at the University of British Columbia, who wasn't involved in the study. The team focused particularly on the role viruses play in carbon sequestration. Every day, massive numbers of dead plankton sink to the bottom of the ocean, taking the carbon in their bodies with them, which is then entombed for potentially millions of years. This process, known as the biological carbon pump, puts away as much as 12 gigatonnes of carbon each year. That is about a third of the total annual human-caused CO2 emissions.

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