The chemical dispersant sprayed on the 2010 Gulf of Mexico oil spill appeared to be successful in removing oil from the water's surface, but it actually hurt bacteria that were helping clean up, according to a new study which suggests that up to half of the oil can't be accounted for and may now be lying on the ocean floor, reports The Telegraph.
After the BP Deepwater Horizon disaster in 2010, which spilled 172 million gallons of oil into the Gulf, the chemical dispersant Corexit 9500 was sprayed on the slick from airplanes because scientists thought that the agent would help degrade the spill and help ocean bacteria eat the oil quicker, according to RT.
The oil on the surface of the ocean appeared to be getting clearer, but officials failed to properly monitor the microbes and chemicals, according to Samantha Joye, a marine scientist at University of Georgia.
Joye's team recreated the chemical application in a lab using samples of the dispersant, BP oil and sea water from the Gulf of Mexico. They found that the chemical didn't aid the oil-munching microbes at all, and even harmed one key bacteria, as noted in the study published Monday in the journal Proceedings of the National Academy of Sciences.
"The dispersants did a great job in that they got the oil off the surface," Joye said, reported The Associated Press. "What you see is the dispersants didn't ramp up biodegradation."
Even more surprising, Joye said her team found that the oil with no added dispersants "degraded a 'heckuva' lot faster than the oil with dispersants."
The researchers examined nearly 50,000 species of bacteria from the Gulf of Mexico and compared how they performed in the water with oil, and in the water with oil and the dispersant, according to AP.
The main oil-eating bacteria that live in the Gulf of Mexico are tiny sausage-shaped organisms called marinobacters. They make up about 3 percent of the bacteria in normal water, but when oil was present, they fed on the oil and multiplied until they comprised 42 percent of the bacteria, according to Joye.
When researchers applied the chemical dispersant, the marinobacters didn't grow at all and stayed at around 3 percent, Joye said. Instead, another type of bacteria called colwellia continued to multiply, but they were far less efficient at eating oil, according to Joye.
With the findings showing that the oil wasn't degraded by the bacteria as previously thought, the scientists hypothesized that the missing oil may have sunk to the floor of the Gulf.
A spokeswoman with the National Oceanic and Atmospheric Administration welcomed the findings and said the agency will further evaluate the effectiveness of dispersants, according to AP.