Wednesday, May 27, 2015

Scientists Map 5,000 New Ocean Viruses

In March 2011, the Tara, a 36-meter schooner, sailed from Chile to Easter Island — a three-week leg of a five-year global scientific expedition. All but one of the seven scientists aboard the ship spent much of their time on the sun-drenched deck hauling up wondrous creatures such as luminous blue jellyfish and insects known as sea-skaters, which spend their entire lives skimming the surface of the ocean far from land.

At the stern of the Tara, a shipping container was bolted to the deck, with a door and a tiny window cut through the metal walls. One of the scientists, Melissa Duhaime, spent most of the voyage inside the dark, tiny cell, where she fought off an endless bout of seasickness.

“People would come in to see what I was doing and leave pretty quickly,” Duhaime said.

Inside her cell, Duhaime sat next to a hose as wide as an outstretched hand. A pump drew water through the hose from several meters below the boat and then pushed it through a series of filters. Each filter was finer than the last, blocking smaller and smaller life forms. The setup stopped animals first, then zooplankton and algae. The last filter in the hose, with pores just 220 nanometers wide, was fine enough to block bacteria. Scrubbed of all these living things, the water finally flowed into three 30-liter vats.

To the untrained eye, these vats might seem to be full of sterile water. But they were seething with ocean life — or life-like things, at the very least. The three vats held up to 1 trillion viruses.

The ocean contains many mysteries, but none so great as its viruses. Scientists estimate that there are 1,000,000,000,000,000,000,000,000,000,000 virus particles in all the world’s seas. They outnumber all cellular life forms by roughly a factor of 10. Scientists have been dimly aware of the staggering scale of the ocean’s virosphere since the late 1980s, but many of the simplest questions about it remained open for years. Scientists couldn’t even say how many species of viruses there were in the oceans. It’s as if zoologists were dimly aware that many places on Earth were home to things called mammals, but their knowledge was based only on a few squirrels in a cage.

Duhaime and her colleagues joined the Tara Oceans Expedition to change that, by collecting ocean viruses on a scale never attempted before. As they report in the May 22 issue of Science, they gathered enough samples to confidently estimate the total number of distinct populations of viruses in the sunlit upper reaches of the ocean. Out of the 5,476 populations they identified, only 39 were previously known to science.

The researchers have gone on to study where these species live and how they affect the ocean’s ecosystems. For years, scientists have suspected that viruses alter the very chemistry of the world’s oceans and may even influence the planet’s climate. Now, the data from the Tara are going to give researchers a much better handle on the full power of the ocean’s viruses.

by Carl Zimmer, Quanta | Read more:
Image: Jennifer Brum, Tucson Marine Phage Lab