Oil began gushing from the BP-Horizon Macondo well into the waters of Gulf of Mexico on the night of April 20th with the explosion of the Deepwater Horizon oil rig. The blowout preventer failed that night and in subsequent days BP was unable to trigger the device. Finally, BP sealed shut a provisional cap over the wellhead and stopped the oil from flowing into the Gulf of Mexico on July 15, 2010, after eighty six days later and an estimated 205,800,000 gallons of oil were released into the Gulf of Mexico.
Nonetheless, the new cap has only been a temporary solution. Permanently plugging the leak will take place early next month using the relief well that has been drilled. A relief well is actually an intercept well that will be used to cut into the Macondo well and pump in mud and cement to permanently seal it. There is risk that in an attempt to permanently seal the well, oil will be released again. So, as both a safety precaution and a collection of evidence in investigating the leak, BP is preparing to remove the failed blowout preventer and capping stack from the damaged Macondo oil well in the Gulf of Mexico. The failed blowout preventer is expected to be removed on Monday or Tuesday and replaced with another blowout before the weekend according to the National Incident Commander Thad Allen. Allen said the blowout preventer is a key piece of evidence in the investigation of the explosion and oil spill, including those by the U.S. Department of Justice and a joint probe by the Coast Guard and the U.S. Bureau of Ocean Energy Management.
Meanwhile, there has been keen interest and worry about the environmental impact from the oil spill. The US government now reports a total of 45,840,000 gallons of oil have been recovered or burned. A total of more than 11,140,000 gallons of oil from the open water have been removed by controlled burns. The government lists 34,700,000 gallons of an oil-water mix have been recovered. In an effort to accelerate the breakdown of the oil approximately 1.84 million gallons of dispersants had been released into the waters of the Gulf of Mexico, both on the surface and in the sub-sea. The long term impacts of this release especially the deep water release of dispersants is unknown, but the underwater plume of oil that was previously observed now appears to be gone.
Several teams of scientists have been following and investigating the oil plume that formed deep below the surface. The plume was created when the chemical dispersant (Corexit 9500) was dumped around the wellhead in an effort to break up the torrent of crude oil gushing from the seabed and prevent a large quantity of flammable oil from reaching the surface. The plume continued spreading through the water even after the well was finally plugged July 15 but has not been observed recently. Several scientific groups have been investigating this plume and its apparent fate.
Terry Hazen is a microbial ecologist with Lawrence Berkeley National Laboratory Earth Sciences Division, (Berkley Lab) and principal investigator with the Energy Biosciences Institute, lead a study from Berkeley Lab. Hazen and his team reported on the new microbes in the online journal Sciencexpress in August. He conducted this research under an existing grant he holds with the Energy Biosciences Institute (EBI) to study microbial enhanced hydrocarbon recovery. EBI is a partnership led by the University of California (UC) Berkeley and including Berkeley Lab and the University of Illinois that is funded by a $500 million, 10-year grant from BP. Results reported in Sciencexpress are based on the analysis of more than 200 samples collected from 17 deepwater sites between May 25 and June 2, 2010.
Hazen and his colleagues determined that natural bioremediation of the oil plum is taking place. They found that microbial activity is causing faster than expected biodegradation. Their research found that the dominant microbe in the oil plume is a new species, closely related to members of Oceanospirillales family of known microbes. The Berkeley Scientists attribute the faster than anticipated rates of biodegradation at the 4.7 degree Celsius temperature several thousand feet below the surface in part to the nature of the Gulf light crude, which contains a large volatile component that is more biodegradable, to the use of the dispersant.
Both the Berkeley Lab and the Wood Hole Oceanographic Institute had found only mildly depressed levels of oxygen (from 67% oxygen saturation outside the plume to 59% saturation within the plume). Wood Hole Oceanographic Institute had reported earlier that the lack of oxygen dead zone anticipated by predicted bacterial digestion of the plume indicated that the plume was being bioremediated slower than expected. While their observations explain the lack of a dead zone, do not explain the disappearance of the plume.
A third group of scientists at University of California at Santa Barbara, who are also attempting to characterize the microbial response to the oil plume felt that the Berkeley Scientists were measuring the dilution rate for the plume more so than the bioremediation rate. Dr. Hazen agreed that dilution was a factor. The Berkeley Scientists will continue to sample the area in the coming weeks including sediment cores near the well head. However, recent observations confirmed that the plume may be gone, thanks to a combination of microbial action and dilution. While the new species of microbe may not be quite as miraculous as its press coverage, still, microbes are present, oxygen saturation while mildly depressed has not created dead zones in the Gulf of Mexico and the plume is gone.