Scientists of the rockpool help tiniest starfish to twinkle amid the pollution

A rare species of tiny starfish virtually wiped out when the Sea Empress tanker shed more than 70,000 tonnes of crude oil on the Pembrokeshire coast 12 months ago may be getting a helping hand to regenerate its numbers thanks to a sophisticated process of DNA match-making.

The brooding cushion star - so named because it incubates its eggs - was flourishing in rock pools at West Angle Bay until heavy pollution from the tanker reduced numbers from an estimated 150 to approximately 12.

More seriously still, the remaining Pembrokeshire population failed to breed last year and the end of its three- to four-year life cycle is now approaching. According to experts from King's College, London, and the Field Studies Council who have been monitoring it, the Welsh cushion star is considered to be functionally extinct without man's intervention.

"The hermaphrodite brooding cushion star needs to aggregate in order to breed," Dr Roland Emson, senior lecturer in biology at King's College, explained. "Even if they are only separated by a few metres within a rock pool they cannot locate each other in order for this to happen. Surveys carried out four months and eight months after the spill indicate that the remaining population is too widely scattered for reproduction to take place."

The only hope of regenerating the colony in West Angle Bay - where it was first identified as a separate species in the mid-Seventies - is by extracting DNA from its tube feet and from those of specimens inhabiting similar terrain in south Devon and creating a genetic picture to see if the two are sufficiently compatible to breed.

Andy Simms, assistant warden and deputy director of studies at the Field Studies Council's Orielton Field Centre, Dyfed, hopes compatibility can be confirmed as he is anxious about the long-term consequences for the rock pool community in the bay should the starfish disappear.

"The removal of any organism can be a negative thing as the stability of the marine community living in those pools is inevitably weakened," he said. "It is rather like the house-of-cards effect, keep taking the cards away and eventually the whole thing will collapse."

"Whether or not the brooding cushion star is a keystone species has yet to be established, but one of the reasons this site is extremely special is because it is so rich in terms of biodiversity and it would be a great pity for that abundance to diminish."