Credit: Flickr user southerntabitha
The oil spill in the Gulf of Mexico was one of the most frustrating disasters in recent memory. As it unfolded, seemingly in slow motion, each item of news added more misery. In April, we learned of an epic explosion on a deepwater oil rig. Next came news of the tragic deaths of 11 workers. Then, the rig itself sank, leaving a growing slick of oil. Over the following weeks, estimates of the oil flow rate steadily increased. In a society grown accustomed to rapid response and instant information, it became clear that the spill could not be stopped quickly: At best, it would take months to stop the oil flow, and not before millions of liters of oil poured into the gulf, threatening both wildlife and the way of life of the human residents of the fragile US Gulf Coast. When the well was finally capped on July 15, nearly three months after the disaster began, there was a collective sigh of relief, but scientists had yet to weigh in on how bad the damage really was—and the cap in place today is still considered to be temporary.
The good news seemed to be that much of the oil had simply disappeared. Little was visible on the surface, beaches had come out relatively unscathed, and while some suspected large volumes of oil were still suspended in underwater plumes, the damage didn’t appear to be nearly as bad as might be expected from the largest accidental oil spill in history.
So where did all that oil go? The anonymous soil microbiologist who blogs at Microbial Modus discusses an August report suggesting that oil-degrading microbes have rapidly adapted to the new conditions in the Gulf and are quickly consuming the oil that remains suspended under the surface. The researchers, led by Terry Hazen, speculate that these oil-consuming bacteria have inhabited the Gulf for far longer than people have, sustained by much slower, natural oil seepage. When the large spill occurred, they were able to reproduce rapidly, adapting to the different chemicals present in the spill area. In short, the bacteria specialized, some tackling the oil itself, some consuming by-products of the oil’s degradation. The research was published in Science.
The bacteria may have gotten an assist from chemical dispersants dispensed both from airplanes and at the wellhead itself. These chemicals are similar to laundry detergents, breaking the large slicks of oil into more manageable drops, about 1-10 micrometers in diameter. But while dispersants may help bacteria, their effects on other wildlife are less certain. Over 4 million liters of dispersants were dispensed at the wellhead alone. What kind of effect does that have? As genetics researcher Holly Bik points out, we really don’t know. While the dispersants themselves are less toxic than oil—and the disaster spilled around 100 times more oil than dispersants—when the oil is chemically dispersed, it becomes more toxic to marine life than it would be in raw form. When this dispersed oil is exposed to sunlight, it can become more toxic still. Bik also notes that the real-world effectiveness of dispersants is far from solid science. While dispersants do seem to promote biodegradation of oil in warmer water, biodegradation in the cold, deep waters around the well proceeds much slower, in some cases barely faster than in undispersed oil. So dispersants may give us poor results in either case: Poor effectiveness in deep water, and an increase in toxicity in warmer water exposed to sunlight.
What does this mean for humans? The science consultant who blogs as “Ashartus” says that while we don’t know yet what the effects of this latest spill will be, we can learn something from previous spills. A team led by Francisco Aguilera reviewed several studies on the effects of spills. In one case, rats were fed mussels contaminated by a spill, and researchers found evidence of DNA damage in the rats—a potential precursor to cancer. However, with the exception of psychological trauma, other studies found minimal short-term health effects in communities near spills. Only people directly involved with cleanup seemed to show any significant health problems as a direct result of oil spills. The research was published in the Journal of Applied Toxicology. But, as Ashartus warns, every oil spill is different, so it’s not necessarily reasonable to extrapolate the effects of other, less-serious spills to this gargantuan disaster. In any case, the results certainly suggest caution when consuming seafood—especially shellfish—that may have been tainted by oil or dispersants.
Dave Munger is editor of ResearchBlogging.org, where you can find thousands of blog posts on this and myriad other topics. Each week, he writes about recent posts on peer-reviewed research from across the blogosphere. See previous Research Blogging columns »
Originally published September 8, 2010
