Around-the-World Expedition Finds 200,000 Species Of Viruses In The Oceans

The Tara sailing in the arctic. (Photo: Tara Ocean)

After travelling around the world, sampling the ocean from pole to pole, scientists have uncovered nearly 200,000 populations of marine viruses.

In the marine ecosystem, tiny living things called microbes make up most of the ocean’s biodiversity and over half of its biomass. But much less is known about the viruses—packets of genetic information that replicate inside other living things—that exist in the oceans.

Scientists set out to study the marine viral community, its diversity, and its function, especially how it impacts microbes. On Thursday, they announced the creation of an enormous, global catalogue of marine viruses, marking an important step in answering many of these questions.

“It expands our knowledge of what the biological entities on our planet are,” Ann Gregory, study author and postdoctoral researcher at VIB-KU Leuven in Belgium, told Gizmodo.

The data comes from 146 samples taken on several expeditions aboard the the schooner Tara, including 41 samples from a 2013 trip to the Arctic Ocean. The researchers first needed to identify whether the genetic material in the sample was viral or not, with various bioinformatic tools comparing it to known viruses, explained study co-author Ahmed Zayed, graduate student at the Ohio State University. Then, they compare the DNA strands to one another in order to divide them into viral populations.

The analysis revealed 195,728 populations of viruses, 12 times more than the previous analysis on a smaller Tara dataset, according to the paper published in Cell.

A closer look revealed that these populations seem to sort into five meta-communities, which the researchers call ecological zones: Arctic; Antarctic; deeper than 2,000 meters; 150 to 1,000 meters; and temperate/tropical waters with depths of 0 to 150 meters. Perhaps surprisingly, latitude didn’t predict viral diversity.

It’s an exciting piece of work. Microbes are perhaps the key drivers of the ocean’s biochemical processes, and microbes are infected by viruses. “I think that people are aware that viral diversity far exceeds that of the vast microbial diversity,” Alison Buchan, professor at the University of Tennessee, Knoxville, told Gizmodo. “But there have not been a great number of studies that have tried to quantify the extent of that diversity.”

What do you do with such a large dataset? Mainly, you research it to try to better understand the roles of all these viruses. Like how the rabies virus can increase the aggression of an infected animal to facilitate transmission, maybe some of these viruses are important for the ocean’s chemical processes. Many of them also lead to the death of the microbes. And maybe this vast new store of genetic information contains something that will be useful to humans.

“Perhaps you can mine it for new genes,” Gregory said. May researchers will discover novel antibiotics using this genetic information.

This dataset is certainly not comprehensive, Gregory and Zayed warned. It includes only viruses that contain DNA, rather than those that contain RNA (somewhat simply, DNA is composed of a pair of complimentary strands of genetic material, while RNA is composed of a single strand). Buchan also noted that it’s more of a snapshot in time. Six months later, they might have collected different results, she said.

This research is a great reminder that, as much as we know about life on Earth, the oceans remain full of unknowns.

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