Science - May 12, 2010

Oil affects fish livers

The oil leak in the Gulf of Mexico is disgorging about 800 thousand litres of oil a day into the sea. Ecotoxicologist John Schobben, head of the Environment department at Imares, says this oil disaster is not like others. 'Some of the impact on the environment is much less visible.'

'It is the floating oil slick that stands out most in this oil disaster. Birds that get covered in oil are destined to die. They lose the ability to fly and float on the water, and their feathers no longer insulate them. But the unobserved effects could well be just as serious. The oil we are dealing with here is a light oil. That means it contains less tar but more relatively soluble compounds such as the infamous PAHs. The fact that the oil is flowing one and a half kilometres from the leak on the ocean floor to the surface means those PAHs dissolve in the seawater. They then end up mainly in shellfish and fish. The fish convert these compounds, producing breakdown products that can cause tumours in fish livers.
'I think the Americans are on the right track in the way they are tackling the problem. They are putting up shields along the coast to keep the floating oil slick away from the sensitive marshes. They are also trying to dissolve the oil using soap-like materials. That is good for the birds, but it does mean you are shifting the problem to the fish and shellfish. The resulting oil emulsion has huge consequences for water filterers like mussels and oysters. Oyster beds may be affected. It is likely that there will be a temporary ban on shellfish catches. It will take a good six years before the marine life has recovered.  
'If as a society you allow drilling along the coast, you are accepting that things can go wrong occasionally. However, the impact of an accident is huge in some vulnerable areas. The Mississippi delta, which is now under threat from the oil, is a very valuable area ecologically. If you start drilling fifty to eighty kilometres away, you are taking a real risk.
'You should be thorough in your risk analyses. You should also look at alternative options to drilling at a particular spot. Stringent rules and compliance with those rules are essential preconditions for responsible oil exploration along the coast.'