Image: Foraminifera
Copyright 2005 AAAS
Hundreds of single-celled organisms known as foraminifera were found in a sample of sediment collected from the Challenger Deep, including these spherical creatures known as organic-walled allogromiids. Reprinted with permission from Science (307:689 (2005)).
updated 2/3/2005 4:47:24 PM ET 2005-02-03T21:47:24

Tiny single-celled organisms, many of them previously unknown, have been discovered beneath nearly seven miles of water (11 kilometers) in the deepest part of the ocean.

A sample of sediment collected from the Challenger Deep southwest of Guam in the Pacific Ocean islands yielded several hundred foraminifera, a type of plankton that is usually abundant near the ocean surface.

“On the species level, all the species we found from the Challenger Deep are quite new,” researcher Hiroshi Kitazato said via e-mail.

Differences in the details
The outer shapes are similar to other known foraminifera, but details of their structure differ, explained Kitazato, of the Institute for Research on Earth Evolution at the Japan Agency for Marine-Earth Science and Technology.

“I am very surprised that so many very simple, soft-shelled foraminifera are dwelling at the deepest point of the world ocean,” he added.

“It is also exciting that most of the group belong to the oldest branch of foraminifera,” he added, suggesting that these deep locations may form some sort of refuge for them.

These distinct creatures probably represent the remnants of a deep-dwelling group that was able to adapt to the high pressures, the researchers suggest in reporting the find. Their discovery is reported in this week’s issue of the journal Science.

Found amid crushing pressure
Because the water is so deep, the pressure where the find was made is 1,100 times more than normal atmospheric pressure at the surface.

While many foraminifera have hard shells, the researchers noted that this newly found group does not.

Similar, though not identical, groups have been found in other, slightly shallower, ocean trenches, they note.

The creatures probably can exist by ingesting particles of organic matter that drift down from above or materials that are dissolved in the seawater, Kitazato said.

The research was funded by the Japan Agency for Marine-Earth Science and Technology, the Japan Society for Promotion of Science, the Kaplan Foundation and the Natural Environment Research Council.

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