Thousands of marine species eke out an existence in the ocean's pitch-black depths by feeding on the snowlike decaying matter that cascades down, and even sunken whale bones, according to a report released yesterday.
Oil and methane also are an energy source for the bottom-dwellers, the report says.
The findings on the deep sea were the latest special update on a 10-year census of marine life, an effort by more than 2,000 scientists from 80 countries to catalog the oceans' species.
Researchers say that since the census began in 2000, they have recorded 17,650 species living below 656 feet, the point where sunlight ceases. They say they have found 5,722 species living in the extreme depths, waters deeper than 3,280 feet.
"Parts of the deep sea that we assumed were homogenous are actually quite complex," said Robert S. Carney, an oceanographer at Louisiana State University and a lead researcher on the deep seas.
The creatures are as weird and outlandish as the creations in a Dr. Seuss book: Tentacled transparent sea cucumbers; primitive "dumbos" that flap ear-like fins; and tubeworms that feed on oil deposits. The census also records the familiar dwellers of the abyss -- squids, hermit crabs and jellyfish.
"The deep sea was considered a desert until not so long ago; it's quite amazing to have documented close to 20,000 forms of life in a zone that was thought to be barren," said Jesse Ausubel with the Alfred P. Sloan Foundation, a sponsor of the census. "The deep sea is the least explored environment on earth."
In all, the census researchers have so far found about 5,600 new species on top of the 230,000 known. They hope to add several thousand more by October 2010, when the census will be done. The scientists say they could announce that a million or more species remain unknown. On land, biologists have catalogued about 1.5 million plants and animals.
Researching the abyss has been costly and difficult because it involved deep-towed cameras, sonar and remotely operated vehicles that cost $50,000 a day to operate, Carney said.
Odd Aksel Bergstad, an oceanographer with the University of Bergen in Norway who was reached by telephone in the Azores islands, said his team of researchers in the Mid-Atlantic Ridge explored the unknown.
"There were not even good maps for the area," Bergstad said. "Our understanding of the biodiversity there was very weak."
In the mid-Atlantic, researchers found 40 new species and 1,000 in all, he said. "It was a surprise to me to find such rich communities in the middle of the ocean."
Once the census is complete, the plan is to publish three books: a popular survey of sea life, a second book with chapters for each working group and a third focusing on biodiversity.
Ausubel said that a census of marine species has never been done. He said some researchers are considering to follow up the 2010 marine census with a 2020 census.
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