Saturday, December 17, 2005

`Dead Zone' Off Sumatra May Be Linked to Quake, Scientists Say

Dec. 14 (Bloomberg) -- Scientists have discovered a mysterious ``dead zone'' in the ocean, a stretch of water without signs of animal life, and they say a deadly 2004 earthquake may be responsible.

The zone was found last April off the shore of Sumatra, Indonesia's largest island, by biologists working for the Census of Marine Life, an international project to study the diversity, distribution and abundance of ocean species, according to a statement released today by the Washington-based group.

``This particular zone may have been the result of the collapse of a cliff during earthquake activity,'' Ronald O'Dor, 61, the chief scientist for the census, said in a telephone interview yesterday. ``I view this as a curiosity.''

The possibility of a dead zone is unprecedented in 25 years of deep-sea sampling, the researchers said. The concept will now have to be taken into account as scientists at the mid-point of a 10-year project continue to conduct their census of ocean life, O'Dor said.

The dead zone was found during an 11-hour dive 4,000 meters (2.5 miles) under the surface of the ocean. While the zone may have been created by the earthquake, which was the largest in the last 40 years, the researchers said that's not a certainty.

``We don't know whether the lack of animals is natural or the function of some tectonic movement there,'' said Paul Tyler, a 59-year-old professor of deep-sea biology at the University of Southampton in England, in a telephone interview yesterday.

Tectonic Plates

The earth's surface is broken into tectonic plates whose movements cause earthquakes. The Sumatra-Andaman Islands undersea earthquake occurred in December 2004 off the west coast of northern Sumatra.

Tyler said the zone without fauna was too deep under water to have been created by the tsunami, the series of waves -- set off by the earthquake -- that killed hundreds of thousands of people in Indonesia, India, Sri Lanka, Thailand and other countries.

The finding near Sumatra was included in a news release by the group highlighting its ocean research. Among other developments, the scientists reported that a single bluefin tuna whose movements were tracked by satellite had completed three crossings of the Pacific in 600 days.

Tuna travel faster than scientists used to think, so that some tuna counted in one spot may be the same ones registered elsewhere, O'Dor said.

``Our estimate of the total number of tuna may be wrong by a factor of two, at least,'' meaning that stocks that can be harvested for food are smaller than earlier believed, O'Dor said.

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