Is an Oil Spill Ever Good for Animals?

Worms love it.

Brown pelicans covered in oil from the Gulf spill. Click image to expand.
Brown pelicans covered in oil from the Gulf spill

The BP oil spill could take a major toll on the Gulf Coast’s wildlife, say marine scientists. We’re already seeing some evidence of die-offs (PDF) among marine mammals, birds, and sea turtles. Are there any species that might actually benefit from the disaster?

Yes. Scientists don’t know what makes it so resilient to the health effects of oil, but the blood-red-colored bristle worm known as Capitella capitata seems able to survive in a polluted environment. Indeed, it thrives. The worm’s natural predators—shrimp, fish, and crabs—start to die off after a spill, leaving room for what’s called ecological succession: The population of one species grows to fill a gap left by damage to another.

At up to 10 centimeters in length and about the width of a human hair, Capitella capitata may seem like the oil spill’s tiny grim reaper. In fact, it could help to restore the Gulf ecosystem. The animals burrow into the sea floor to feed on organic matter deposited there. This movement circulates new water into the sediments and addresses one of the major problems after an oil spill—the depletion of oxygen in the ocean by the hungry bacteria that are working to break down pollutants. By churning up mud at the bottom of the Gulf, the worms release and recycle pockets of anoxic water, which in turn allows sediment bacteria to degrade more oil. (The flourishing micro-organisms also serve as food for the bristle worms.) The ecological interplay between worms and bacteria paves the way for the return of other species. Bolstered by higher oxygen levels and more worms to eat, the populations of fish, crab, and shrimp begin to increase.

Capitella capitata is known as an indicator species, which means biologists rely on it to assess the condition of a particular environment. A large number of worms suggests poor water quality, but with the potential for improvement. For example, Capitella has been tracked in water near sewage outfalls, such as parts of Boston Harbor, as a way of assessing cleanup efforts. It’s not yet clear whether Capitella numbers are increasing in the Gulf. Due to the extent of the cleanup—thousands of barrels of oil are still leaking into the ocean daily—it may be months before worm-tracking scientists have access to the sediment.

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Explainer thanks Adam G. Marsh of the University of Delaware, James Blake of the ENSR Marine and Coastal Center, John Fleeger of Louisiana State University, Judith Grassle of Rutgers University, Nancy Rabalais of the Louisiana Universities Marine Consortium, and Mary Wicksten of Texas A&M.

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