Known as the largest marine oil spill in history, the Deepwater Horizon Spill or also referred as the Gulf of Mexico oil spill, killed 11 workers five years ago, and more than 4.9 million barrels of oil were dicharged, damaging marine habitats and wildlife.
After this event, the authorities sent planes to spray chemical dispersant Corexit 9500 in the oil diffusion. The idea was to break up the spill into smaller droplets until they degradade, helping the natural bacteria in the water to quickly remove oil, preventing it to come to nearby beaches and other protected habitats.
Although the authorities noted that the surface of the affected area seemed to be getting cleaner over the years, bacteria and chemicals were not monitored until a new study made by scientists at the University of Georgia showed that the dispersant didn’t lower the presence of all microbes. Even, it showed that the chemical agent significantly increased the presence of a family of microbes called Colwellia.
Lead autor Samantha Joye and her colleagues, recreated the conditions of the BP oil spill in a lab, closely monitoring the effects of Corexit 9500 on oil slicks and the microbes that feed on them.
They tested with more than 50,000 bacterias and found that Corexit 9500 did not help the growth of one of the main groups of consumers of oil in seawater, Marinobacter, or increase the speed at which microorganisms consume the oil, either in deep water or surface environments. Instead, it actually appeared to inhibit growth. The microorganism was better in water that contains no chemicals.
The study, published in the Proceedings of the National Academy of Sciences, concluded that the chemicals, which were released in deep water as well as on the surface of the Gulf, didn’t cause the microbes to biodegrade the oil, as intended.
The researchers wrote, “Direct measurement of alkane and aromatic hydrocarbon oxidation rates revealed either suppression or no stimulation of oil biodegradation in the presence of dispersants,” according to Discovery News Post.
If the laboratory results hold true in the real world, “Dispersants can exert a negative effect on microbial hydrocarbon degradation rates,” the researchers concluded.
These findings come just a few months after BP accepted it would pay $18.7 billion across a period of 18 years, in order to settle economic and environmental damage claims made by 4 states and over 400 local governments, after breaching the Clean Water Act.