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Home >> Sci-Edu
UPDATED: 08:46, December 16, 2005
There's a whole new world down there, census reveals
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An unprecedented audit of the oceans has discovered hordes of unusual creatures, forcing scientists to rethink their ideas about the world's wildest marine life.

Among the organisms to be identified are tiny carnivorous sea sponges that engulf passing prey with their mouths and single-celled animals that protect themselves by building football-like shells.

The species were spotted by two separate expeditions that set out to probe the little-known depths of the South Atlantic and Southern oceans. Scientists aboard the vessels say that up to 90 per cent of the creatures they encountered have never been seen before.

The expeditions were part of an attempt to draw up a census of life in the world's oceans, the most under-explored environment on Earth. Now at the halfway stage, the GBP500m Census of Marine Life involves 1,700 scientists in 73 countries.

Each week, they add two new species of fish to a database that includes mammals, sea birds, corals, turtles and anemones. Along the mid-Atlantic ridge researchers spotted swimming red sea cucumbers while in the Arctic ocean they discovered red jellyfish that grow up to 3 metres long.

Other creatures detected included a copepod, a shrimp-like crustacean and a jellyfish in the depths of the Canada basin far beyond its known range.

The census now totals more than 40,000 species, including 15,717 fish, although researchers believe this is merely the tip of the iceberg. "We estimate there are around 230,000 species down there and we want all of those documented by the end of the census in 2010. But that's a conservative estimate. We could well find a million new species by then," said Ron O'Dor of Dalhousie University in Canada and leading researcher on the census.

Biologists also looked for life near the epicentre of the earthquake that triggered the tsunami off Sumatra on the December 26 last year. Around the earthquake zone, there was little sign of any serious damage to wildlife, but closer by they found a dead zone where 11 hours of dives found no evidence of the large marine animals usually found in the region.

Some smaller organisms such as the sea cucumber were also missing. According to the researchers, the absence of life was "unprecedented."

Key to the census is a silent-running vessel called GeoSars which carries the world's most sensitive sonar. The ship can detect creatures the size of a shrimp at a depth of 3 kilometres. The average depth of the oceans around the world is about 4 kilometres, giving the ship access to all but the deepest waters.

While some scientists focus on auditing species, others have implanted transmitters into fish and other creatures to track their movements. One bluefin tuna tagged with a transmitter stunned scientists by making three crossings of the Pacific Ocean in 600 days, covering a distance greater than Earth's circumference. Tracking fish has revealed some uncomfortable truths for those managing fish stocks. Computer models of fish abundance have proved, in many cases, to be simplistic.

"One of the reasons for the collapse of cod stocks is that we didn't understand their movements," said Dr O'Dor.

"We thought that if we just shut down the fisheries, they'd all come back, but that hasn't happened. It turns out they all feed together in a particular place, then separate, with breeding stocks going to different spots. The fisheries went in and knocked out entire breeding stocks one by one."

Source: China Daily

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