The Shetland Oil Disaster: Nature knows best how to recover from pollution

FOR ALL practical purposes, no one will be able to tell in five to ten years' time that the Braer ran aground, so powerful are natural processes of regeneration.

The best way to clean up the spill is to let Mother Nature do the work, marine biologists say. But nature can be helped. By spraying dispersants from aircraft, the oil can be broken up into droplets, sinking to deeper water where natural oil-loving bacteria degrade and digest it.

Dr Peter Donkin, from the Plymouth Marine Laboratory, said a technique used successfully with the Exxon Valdez spill was to spray a mixture of microbes and fertiliser on to the oil to kick-start the natural process of degradation.

Some of the Braer's cargo of light crude will evaporate and blow away with the winds, while some of the remainder will be water-soluble, so a substantial proportion will disappear without intervention.

According to Dr Donkin, the procedure in Britain is to attack slicks at sea to sink and disperse oil, to let waves clean contaminated rocks on shore and to skim the top layer of sand off beaches. The priority is to spray dispersants on oil to remove it from the surface and to prevent wind and waves fluffing it up into 'chocolate mousse' - an emulsified mix, about 70 per cent water with oil and some air.

Dave Neilson, of the Oil Spill Services Centre at Southampton, said the 'chocolate mousse' phase greatly increases the volumes needed to be sucked up by skimmers and other pumping equipment, making life more difficult for oil-removers.

If oil reaches rocky shores, British practice is to leave it alone. American authorities have been criticised for steam cleaning rocks contaminated when Exxon Valdez oil came ashore in Alaska - allegedly they parboiled organisms that would have survived the oil.

Some life such as limpets and whelks on a shoreline covered in oil will die, but toxic detergents could increase the short- term toll. For small marine life, oil is not the instant killer portrayed, acting first as a narcotic. If the oil washes away on the next tide, the organisms will recover.