Oil Spill Surface Cleanup Ignores Fish Below

April 10, 2009 -- Birds are the most high-profile victims of oceanic oil spills, but fish suffer from these messy accidents, too. Even worse, a new study suggests, the chemicals commonly used to clean up oil spills make oil far more toxic to fish, particularly for eggs and young fish.

Scientists already debate about how best to clean up spills. The new work makes those decisions even more complicated and controversial.

"While you can see the risk on the surface, appreciating risk under the surface is much more difficult," said Peter Hodson, a fish toxicologist at Queen's University in Kingston, Ontario. "You're trading off one set of risks that are fairly clear for another set of risks that are not so clear."

Oil and water don't normally mix. So, when a truck, train, or ship accidentally dumps its cargo into a lake, stream or sea, the oil sits on top of the water and spreads across its surface. The slick substance then flows with the currents and tides, poisoning the animals it encounters along its way.

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On the scene of a spill, difficult decisions need to be made quickly. In an ideal world, the rescue team would simply skim all the oil off the surface, said Nancy Kinner, co-director of the Coastal Response Research Center at the University of New Hampshire in Durham.

In reality, even the best equipment leaves a lot of oil behind. What's more, most spills happen during storms, making cleanup dangerous and difficult. According to policy, Kinner said, crews simply won't go out on the water if there is a risk of capsizing.

Another way to get oil off the surface is to use a chemical dispersing agent. These detergent-based substances cause oil to bead up into tiny droplets that can mix into the water and disperse into deeper layers. Underwater currents can then theoretically dilute the oil and its risk to the environment.