The world watched in horror a year ago as the Deepwater Horizon oil spill spread a dark stain over the Gulf of Mexico. The media eagerly reported oil and dead animals on the beaches of the southern US, but there was great uncertainty over what the release of that much oil (approximately 779 million liters) would do to the Gulf's ecosystem. BP, the EPA, and conservationists all had their guesses, but the real answer was that no one knew. Environmental scientists have studied the biology of oil and other hydrocarbons in the environment, but the Gulf of Mexico's ecosystem is vast, complex, and, like many ecosystems, difficult to predict. Additionally, it's impossible to "do the experiment": one can't exactly create a large-scale oil spill to test one's predictions.
However, studies of the environmental effects of oil spills such as Deepwater Horizon and the Exxon Valdez spill in Prince William Sound off the coast of Alaska have taught us much about how ecosystems deal with oil contamination. A recent publication in Environmental Science & Technology compares and contrasts these two disasters and concluded that in both cases, "oil-eating" microbes like bacteria and fungi were the major players in destroying the released oil.
Oil and other naturally-occurring hydrocarbons leak into the environment in small doses, and certain microbes have adapted to consume these hydrocarbons. These microbes, already present in the environment, usually survive at low populations. When oil is quickly released in large quantities, the microbes are presented with a feast. They reproduce quickly and continue to consume the oil present at ever-increasing rates until the food runs out.
Terry Hazen, microbial ecologist with the Lawrence Berkeley National Laboratory and co-author of the recent EST paper, points out how bioremediation strategies often take advantage of and encourage the microbes' help.
“In the case of the Exxon Valdez spill, nitrogen fertilizers were applied to speed up the rates of oil biodegradation,” Hazen says. “In the case of the BP Deepwater Horizon spill, dispersants, such as Corexit 9500, were used to increase the available surface area and, thus, potentially increase the rates of biodegradation.” (via Lawrence Berkeley National Laboratory)
This isn't to say that oil spills are nothing to worry about. The toll on animal life (including endangered species which may never recover), as well as the loss of revenue from the affected areas can be tremendous. Still, it is amazing how self-correcting our environment can be…given enough time. And oh, you weren't using that beach/ocean/coastline/seabed/animal population in the meantime, were you?
The original paper, “Oil biodegradation and bioremediation: A tale of the two worst spills in U. S. history", is available for free, should you want to exercise your environmental science or hydrocarbon chemistry muscles.