The oceans, cradles of viral diversity

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Photo: Walt Stearns.

New research on data derived mainly from the Tara Oceans expedition in 2009 to 2013 has generated an archive of viruses found in all the world’s oceans.

Led by the University of Ohio in the US, the study, involving teams from several research institutes associated with the Tara Oceans Research Federation has brought the number of identified oceanic viral populations from 16,000 to nearly 200,000. The research was published as the cover story of Cell magazine on May 16, 2019.

The findings show the importance of the oceans as a reservoir of marine viruses and will be referenced extensively for understanding the role of viruses as ocean ecosystems respond to the impacts of climate change.

For the research the Tara Ocean Foundation and partners used the resources of the Tara Oceans expedition to collect and analyze 35,000 samples of marine plankton. More than 200 scientists from some 20 international laboratories were involved.

Viruses play a role in transporting carbon from the surface to the ocean seabed, the “biological pump”. It is therefore essential to identify them and understand their functioning, dynamics and role in marine ecosystems. The study is leading to an understanding of the genetic variation within each virus population, their evolution and the impact of ocean viruses globally.

Viruses impact all other marine planktonic organisms (bacteria, archaea, protists, and animals) and can change the structure of bacteria populations when they colonize them by stimulating their metabolism and modifying their evolutionary trajectory. In this way they can inf luence the ability of the oceans to sequester carbon from the atmosphere.

Micro-organisms in marine plankton play a vital role since they produce more than half of the oxygen we breathe and absorb carbon dioxide from the atmosphere, transferring it to the bottom of the ocean.

By developing new methods to sequence the viruses in planktonic populations, researchers can understand genetic variation between individual organisms within each viral population, between populations within each viral community, and between viral communities across several environments of the oceans, as well as the driving forces behind all these variations.

The global maps of viral diversity are surprising. Almost all virus communities are divided into only five groups, depending on their location and depth.

The greatest viral diversity measured in the Arctic Ocean is astonishing. Most previous studies of uni-cellular and multi-cellular organisms have shown the highest diversity is in the tropics, with decreases as one moves towards the poles. But the new findings suggest for instance, that the Arctic Ocean is a cradle of viral biodiversity, which highlights again the importance of the Arctic (and Antarctic) region for biodiversity.

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