Gigantic Deepwater Horizon oil plume disappeared 2 weeks after well capped
BILOXI, Mississippi — The gigantic deepwater plume of oil that spewed from the broken Deepwater Horizon wellhead disappeared within two weeks of the well being capped, said a scientist speaking on the biodegradation of oil.
Scientists also said the use of dispersants was effective in reducing the impact of the 4.9 million barrels of crude oil that began spilling from the site after an April 20 rig explosion that killed 11 workers.
“This was a gigantic plume,” said Terry Hazen, a professor at the Lawrence Berkeley National Laboratory.
“You couldn’t see it or smell it, but it was the size of Manhattan.”
Hazen was one of Friday’s speakers at a conference on “Vibrios in the Environment” that began Sunday.
The 300 scientists and students attending the conference at the Beau Rivage took a break from their focus on vibrios, a common, sometimes-lethal bacteria, to learn about the oil spill in the Gulf of Mexico.
Hazen said his research team of about 50 people began their oil spill study on May 25 and continued until Oct. 20.
“From July 27 to Aug. 26, we took over 170 samples. We could not find any oil,” he said of the plume that
had spread southwest of the well, which was capped on July 15.
“We don’t believe that plume is out there anymore,” he said.
The plume had been about 1,100 meters below the surface, and was 5 to 10 kilometers wide, 30 kilometers long and 200 meters thick, he said.
But, the massive plume disappeared within two weeks of the well being capped, he said.
Hazen said the oil was never highly concentrated in the plume. The oil concentration in the plume was never higher than 10 parts per million of oil, and averaged 1 part per million, he said.
“I don’t want to give the impression that it just biodegraded. It is also diluted, because the current was moving things and mixing,” he said.
Other scientists credited oil-eating bacteria and the use of dispersants for reducing the impact of the oil on the Gulf of Mexico.
Jay Grimes, a marine microbiologist at the University of Southern Mississippi’s Gulf Coast Research Laboratory, said the use of dispersants was effective.
“They did what they were supposed to, in terms of dispersing the oil and making the oil very, very small —
microscopic — which allowed the bacteria to better colonize the oil droplets and degrade those droplets much quicker,” he said.
“Keeping much of that oil deep in the ocean was much better than having it on the shores of Davis Bayou and all of our other bayous along the coast of Mississippi, where there would be serious effects on spawning grounds for both fish and invertebrates,” Grimes said.
The Gulf’s warm waters are helping decompose the oil, but the oil is going to be around for years, he said.
“The native bacteria decompose this oil very quickly,” he said.
Adverse impacts from the oil should last no longer than two to three years, he said.