Watching the World Ethnic cleansing by the Sea Empress

With David Knott
from London

Ethnic cleansing is a term used in today's news coverage of the civil war in Bosnia to describe wiping out of a minority group of people from an area.

The oil industry inadvertently carried out a marine version of this-you could call it benthic cleansing-with the Sea Empress tanker spill off South Wales.

Sea Empress ran aground on rocks outside Milford Haven harbor Feb. 15. By the time it eventually was refloated Feb. 22, more than half its 130,000 metric tons of crude oil cargo had spilled into the sea (OGJ, Feb. 26, p. 34).

Robin Crump, head of the field studies unit at Dyfed Wildlife Trust, Haverfordwest, Wales, is monitoring the effects of the Sea Empress spill.

Besides a large number of birds expected to be killed by being covered by the oil, Crump expects severe mortality among inshore mollusks. These include limpets, noted for their ability to cling tightly to rocks.

Vulnerable creatures

"After the spill, the limpets can be easily picked off the rocks," Crump said. "They are not so much poisoned as narcotized. But oystercatchers are later poisoned by eating about 50-100 limpets a day. Birds are particularly vulnerable to poisoning by oil through the food chain.

"Besides being eaten by birds, limpets also control seaweed. Kill limpets and you destroy the balance of the whole ecosystem."

Crump also cited the devastating effect of the Sea Empress spill on the local population of a rare species. The Asterina phylactica starfish was discovered only 10 years ago by Crump and a colleague. It lived at only seven sites, all in the U.K. After the Sea Empress spill, only six colonies remain.

"It is a tiny creature, only 10 mm across," Crump said. "One group lived in rock pools in West Angle Bay, but we're now pumping pure crude oil from those pools.

"At that site this starfish has been exterminated. It won't come back because it lays eggs rather than producing planktonic larvae. The mother lays the eggs, broods them over 3 weeks in June, then dies."

Offshore study

While it may be tempting to dismiss the extinction of a group of starfish as an unlucky, one-time event, a study of marine life in the spill area shows there are many more small populations of rare species than might be thought.

For example, Marathon Oil (U.K.) Ltd. found gas with a 1994 wildcat drilled in offshore Block 103/1 (OGJ, Nov. 7, 1994, p. 35). As part of its effort to identify environmental issues there, Marathon sponsored a study of seabed animals in the southern Irish Sea off Wales.

The study, entitled Benthic Biodiversity in the Southern Irish Sea, was carried out by the Department of Zoology at National Museums & Galleries of Wales, Cardiff.

By trawling and dredging, 1,030 species of worms, crustaceans, and mollusks were identified, many unique to the area. In some places there were more than 17,000 creatures/sq m. The authors claimed that 20 species of worms collected in the survey were possibly new to science.

After Sea Empress, Marathon and others aiming to drill off South Wales will be under close scrutiny. Their watchers will be as keen to prevent more local populations being wiped out as any United Nations task force in Bosnia.