Life Is Found Thriving at Ocean's Deepest Point

February 3, 2005

At the ocean's deepest point, the water pressure is the equivalent of having about 50 jumbo jets piled on top of you. Yet even here life thrives, according to scientists who have pulled a plug of dirt from the seafloor.

The sample was taken from the Challenger Deep, which is nearly 7 miles (11 kilometers) deep. The soil was packed with a unique community of mostly soft-walled, singled-celled organisms that are thought to resemble some of the world's earliest life forms.

They're called foraminifera, single-celled protists that construct shells. Protists are a kingdom of celled organisms distinct from animals, plants, and fungi. Other types of protists include algae and slime molds.

There are an estimated 4,000 species of living foraminifera. They inhabit a wide range of marine environments, mostly on the ocean bottom, though some live in the upper 300 feet (100 meters) or so of the ocean. A few species are found in fresh water and on land.

However, the discovery of 432 foraminifera living in dirt from the Challenger Deep surprised Hiroshi Kitazato, a program director at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in Yokosuka.

"We are surprised that so many [bottom dwelling] foraminifera—in particular so [many] soft-shelled forms—live in the Challenger Deep, because former reports gave us the impression the world's deepest point is scarce in any [celled organisms]," he said.

At 36,201 feet (11,034 meters) below sea level, Challenger Deep is the lowest part of the Pacific Ocean's Mariana Trench, located just east of the Philippines.

The sediment core was collected with KAIKO, JAMSTEC's remotely operated vehicle. Kitazato and colleagues report the discovery in tomorrow's issue of the journal Science.

Brian Huber is the curator of foraminifera at the Smithsonian Institution's National Museum of Natural History in Washington, D.C. He said the discovery of abundant soft-walled foraminifera in Challenger Deep is "one more example of how you can find life in the most extreme environments."

In recent years scientists have found bacteria living miles beneath the Earth's surface and snuggled up to scalding hydrothermal vents on the ocean floor. There is even evidence that bacteria live in Antarctic lakes that have been covered by ice for thousands of years.

Jere Lipps, a foraminifera expert in the Department of Integrative Biology at the University of California, Berkeley, is not surprised by the find. He believes foraminifera have lived at such great depths for millions of years and thus are adapted to life there.

However, he said, the discovery raises more questions than it answers—questions "about the distribution, evolution, adaptation to high pressures," and past distribution of foraminifera.

Continued on Next Page >>




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