Plankton is one of the bases of the Earth's food chain, but a new examination of these tiny lifeforms show these organisms are far more diverse than biologists previously believed. Researchers also discovered new forms of life during the most extensive study ever conducted on the organisms.

Tara Oceans Consortium biologists spent almost four years traveling around the globe, collecting 35,000 samples of plankton from 210 locations around the planet. In total, these tiny organisms contained roughly 40 million genes. This is roughly four times the number of genes found among the myriad of organisms living in the human gut. More than 80 percent of the genes identified during the Tara expedition were previously unknown to biologists.

The Tara, a 110-foot schooner, was utilized to travel to each of the world's oceans, where researchers collected plankton samples from the surface of the water down to depths of over 6,500 feet. However, most of the samples collected during the 87,000-mile-long journey were found within the uppermost 650 feet of the ocean's depth.

Plankton not only provide food for marine life from tiny fish to blue whales, but these lifeforms also produce roughly half the oxygen in the Earth's atmosphere. They come in several forms, including minuscule animals, known as zooplankton, and tiny plants, or phytoplankton. They also include free-floating viruses and bacteria.

Although they provide the planet with a greater amount of oxygen than the world's rainforests, relatively little is known about the microorganisms.

Researchers found that most of the interactions between plankton were parasitic, as one organism consumes another. They also discovered evidence of the widespread presence of viruses throughout the oceans of the world. Although great variation in viruses were seen in individual areas, diversity around the globe was not found to be much greater. This suggests these viruses were likely distributed throughout the global ocean by the actions of currents.

"Since the most numerous members of the plankton are bacteria, the majority of viruses in the ocean are thought to infect bacteria. A good way of thinking about this is that there are roughly 200 million viruses in every mouthful of seawater, and most of those viruses are infecting the roughly 20 million bacteria found in every mouthful of seawater," said Jennifer Brum of the University of Arizona.

Because some plankton can take in carbon dioxide and convert the gas to organic carbon, these tiny lifeforms could help the planet absorb a percentage of the greenhouse gases currently leading to global climate change.

Examination of the global plankton populations around the globe was detailed in a series of five articles published in the journal Science.

Photo: Marc de Ruijter | Flickr

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