Ocean experts fathom out sea layers

November 10, 1995

A mission to probe life at the bottom of the Bay of Biscay starts soon with a grant of more than Ecu4 million (Pounds 3.3 million)from the European Union.

The work follows dramatic discoveries over the past decade that parts of the ocean floor are not empty, as scientists had assumed, but teeming with life.

Tony Rice of the Southampton Oceanography Centre, who will coordinate the project, revealed the life forms by placing a "bathysnap" (a time-lapse camera) on the ocean floor in 1981.

Any creatures living there are unable to photosynthesise, which requires sunlight. They depend for their food on plankton drifting down. Dr Rice and his colleagues overturned the idea that there is a slow rain of tiny bits of plankton that can take years to reach the bottom from the ocean surface. Instead they discovered that the organic matter arrives seasonally, and quickly, in big clumps.

The camera showed corresponding surges in lively activity among sea-floor creatures which consume frantically in the right season.

Since this discovery, the team has been snapping away on the sea floor and netting the benthic creatures, which live from just below the ocean floor to about 40 metres up into the water.

In a remarkable 19-month sequence photographed last year, the team saw an eight-metre long worm stick its proboscis out of its burrow, take up food for a while and then disappear.

"We're still in the wondering stage," said Dr Rice. "Every time a dredge comes back there are creatures in it that no one has ever seen before."

Now, the scientists want to help another group that works with the ocean floor: ocean drillers remove long cores of sediment and match the layers with the period of time in which they were deposited.

They thus build up a continuous record of what was happening in the ocean, which gives invaluable insights into, for example, climate.

But Dr Rice is worried about the accuracy with which scientists can attribute certain layers to certain periods. "The top layer of the sediment is churned up by these animals," he said.

If the rate at which sediment accumulates on the ocean floor is a few millimetres per 1,000 years and the animals churn up sediment as deep as ten centimetres then the ocean drillers cannot expect too great a resolution, he said.

The project, funded under the EU's Marine Science and Technology programme (MAST) aims to explore this and other ways in which the benthic layer influences the sediment below.

The project is being undertaken with eight other European countries.

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