http://wildsingaporenews.blogspot.com/2010/08/gulf-oil-spill-giant-underwater-plume.html
19 Aug 10;
WASHINGTON (AFP) – Experts said Thursday they have mapped a 35-kilometer (22 mile) long underwater plume of oil that spewed from BP’s ruptured Gulf of Mexico well, seeming to challenge US government assertions that most of the oil has disappeared.
The oily underwater cloud measured two kilometers wide and 200 meters (650 feet) thick and was drifting through the Gulf at a depth of at least 900 meters, according to the paper by Woods Hole Oceanographic Institution (WHOI) marine biologists, published in the journal Science.
The plume was seen as not dissipating as rapidly as experts had expected, despite widespread use of dispersants which the government has insisted have been vital to the breakdown of vast amounts of oil.
The observations were made in late June, several weeks before the ruptured wellhead was capped, and about two months after an explosion sank the BP-leased Deepwater Horizon rig, triggering the largest ever maritime oil spill.
Challenging US government estimates based on natural processes rapidly dissipating the toxic crude, the authors said deep-sea microbes were degrading the plume only slowly and predicted the oil would endure for some time.
“We’ve shown conclusively not only that a plume exists, but also defined its origin and near-field structure,” said lead author Richard Camilli.
The oil already “is persisting for longer periods than we would have expected,” he added.
“Many people speculated that the sub-surface oil droplets were being easily downgraded. Well, we didn’t find that. We found that it was still there.”
US and BP officials earlier this month proclaimed that about three-quarters of the oil which gushed into the Gulf had been cleaned up or dispersed through natural processes.
Around 4.9 million barrels of oil are believed to have spewed from the fractured wellhead before it was capped last month. US officials say that of that amount, 800,000 barrels were contained and funneled up to ships on the surface.
The leak not only threatened livelihoods of fishermen and tourism businesses along the US Gulf coast, but also stoked fears of long-term ecological damage.
On August 4, the US National Oceanic and Atmospheric Administration (NOAA) said the “vast majority” of oil had been evaporated, removed by cleanup teams or was dispersing naturally.
The remaining 26 percent — or about 1.3 million barrels of oil — was classified as “residual oil” and “is either on or just below the surface as residue and weathered tar balls, has washed ashore or been collected from the shore, or is buried in sand and sediments,” the report said.
The Woods Hole team used a robotic submarine equipped with an underwater mass spectrometer to detect and analyze the plume, making repeated horizontal sweeps to ascertain its size and chemical composition.
They followed the “neutrally buoyant” cloud as it migrated slowly, at 0.27 kilometers per hour, southwest of the leaking well.
The plume was then tracked for a distance of about 35 kilometers before the approach of Hurricane Alex forced the scientists to turn back.
The spectrometer found petroleum hydrocarbons at concentrations of more than 50 micrograms per liter, a level that meant the samples had no smell or oil and were clear. The impacts on biodiversity remain uncertain, though.
“The plume was not a river of Hershey’s Syrup,” said Christopher Reddy, a marine biochemist. “But that’s not to say it isn’t harmful for the environment.”
The damaged well was capped on July 15. Earlier this month BP engineers plugged the site with heavy drilling fluid and then sealed it with cement.
The company aims to permanently seal the well in the second week of September, a US official said on Thursday.
Major study charts long-lasting oil plume in Gulf
Seth Borenstein, Associated Press Yahoo News 20 Aug 10;
WASHINGTON – A 22-mile-long invisible mist of oil is meandering far below the surface of the Gulf of Mexico, where it will probably loiter for months or more, scientists reported Thursday in the first conclusive evidence of an underwater plume from the BP spill.
The most worrisome part is the slow pace at which the oil is breaking down in the cold, 40-degree water, making it a long-lasting but unseen threat to vulnerable marine life, experts said.
Earlier this month, top federal officials declared the oil in the spill was mostly “gone,” and it is gone in the sense you can’t see it. But the chemical ingredients of the oil persist more than a half-mile beneath the surface, researchers found.
And the oil is degrading at one-tenth the pace at which it breaks down at the surface. That means “the plumes could stick around for quite a while,” said study co-author Ben Van Mooy of the Woods Hole Oceanographic Institution in Massachusetts, which led the research published online in the journal Science.
Monty Graham, a scientist at the Dauphin Island Sea Lab in Alabama who was not involved in the study, said: “We absolutely should be concerned that this material is drifting around for who knows how long. They say months in the (research) paper, but more likely we’ll be able to track this stuff for years.”
Late Thursday, federal officials acknowledged the deepwater oil was not degrading as fast as they initially thought, but still was breaking down “relatively rapidly.” Jane Lubchenco, chief of the National Oceanic and Atmospheric Administration, said agency scientists and others were “working furiously” to come up with actual rates of biodegradation.
She noted a bright spot from the slow breakdown of the oil: Faster would mean a big influx of oil-eating microbes. Though they are useful, they also use up oxygen, creating “dead zones” that already plague the Gulf in the summer. Dead zones are not forming because of the oil plume, Lubchenco said.
The underwater oil was measured close to BP’s blown-out well, which is about 40 miles off the Louisiana coast. The plume started three miles from the well and extended more than 20 miles to the southwest. The oil droplets are odorless and too small to be seen by the human eye. If you swam through the plume, you wouldn’t notice it.
“The water samples when we were right in the plume look like spring water,” study chief author Richard Camilli said. “You certainly didn’t see any oil droplets and you certainly didn’t smell it.”
The scientists used complex instruments – including a special underwater mass spectrometer – to detect the chemical signature of the oil that spewed from the BP well after it ruptured April 20. The equipment was carried into the deep by submersible devices.
With more than 57,000 of these measurements, the scientists mapped a huge plume in late June when the well was still leaking. The components of oil were detected in a flow that measured more than a mile wide and more than 650 feet from top to bottom.
Federal officials said there are signs that the plume has started to break into smaller ones since the Woods Hole research cruise ended. But scientists said that wouldn’t lessen the overall harm from the oil.
The oil is at depths of 3,000 to 4,000 feet, far below the environment of the most popular Gulf fish like red snapper, tuna and mackerel. But it is not harmless. These depths are where small fish and crustaceans live. And one of the biggest migrations on Earth involves small fish that go from deep water to more shallow areas, taking nutrients from the ocean depths up to the large fish and mammals.
Those smaller creatures could be harmed by going through the oil, said Larry McKinney, director of Texas A&M University’s Gulf of Mexico research center in Corpus Christi.
Some aspects of that region are so little known that “we might lose species that we don’t know now exist,” said Graham of the Dauphin Island lab.
“This is a highly sensitive ecosystem,” agreed Steve Murawski, chief fisheries scientist for the federal agency NOAA. “The animals down at 3,300 to 3,400 feet grow slowly.” The oil not only has toxic components but could cause genetic problems even at low concentrations, he said.
Lubchenco said NOAA is “very concerned about the impact” of the oil below the surface and federal officials last week started more aggressive monitoring of it.
For much of the summer, the mere existence of underwater plumes of oil was the subject of a debate that at times pitted outside scientists against federal officials who downplayed the idea of plumes of trapped oil. Now federal officials say as much as 42 million gallons of oil may be lurking below the surface in amounts that are much smaller than the width of a human hair.
While federal officials prefer to describe the lurking oil as “an ephemeral cloud,” the Woods Hole scientists use the word “plume” repeatedly.
The study conclusively shows that a plume exists, that it came from the BP well and that it probably never got close to the surface of the Gulf of Mexico, Camilli said. It is probably even larger than 22 miles long, but scientists had to stop measuring because of Hurricane Alex.
Earlier this week a University of South Florida team reported oil in amounts that were toxic to critical plant plankton deep underwater, but the crude was not necessarily in plumes. Those findings have not been reviewed by other scientists or published.
The plume is probably still around, but moving west-southwest of the BP well site at about 4 miles a day, Camilli said.
While praising the study that ended on June 28, Murawski said more recent observations show that the cloud of oil has “broken apart into a bunch of very small features, some them much farther away.” Texas A&M’s McKinney said marine life can suffer harm whether it is several smaller plumes or one giant one.
NOAA redirected much of its sampling for underwater oil after consulting with Woods Hole researchers. The federal agency is now using the techniques that the team pioneered with a robotic sub and an underwater mass spectrometer, Murawski said.
Previous attempts to define the plume were “like watching the Super Bowl on a 12-inch black-and-white TV and we try to bring to the table a 36-inch HD TV,” said Woods Hole scientist Chris Reddy. The paper, fast-tracked for the world of peer-reviewed science, was written on a boat while still in the Gulf, he said.
Reddy said he could not yet explain why the underwater plume formed at that depth. But other experts point to three factors: cold water, the way the oil spewed from the broken well, and the use of massive amounts of dispersants to break up the oil before it gets to the surface.
The decision to use 1.8 million gallons of dispersants amounted to an environmental trade-off – it meant less oil tainting the surface, where there is noticeable and productive life, but the risk of longer-term problems down below.
Retired Coast Guard Adm. Thad Allen, the government’s point man on the Gulf oil spill, said it was a choice between two difficult options – with the discussions going on in front of the president. In the end, officials decided to “accept the implication of the hydrocarbons in the water column rather than Barataria Bay or the Chandeleur Islands” in Louisiana.
Given the slow rate at which the oil is degrading in the cold water, Samantha Joye of the University of Georgia, and others say it is too early to even think about closing the books on the spill: “The full environmental impacts of the spill will thus not be felt for some time.”
Gulf Plume Resists Oil-Eating Microbes
Jeremy Hsu livescience.com Yahoo News 20 Aug 10;
A massive oil plume from the Deepwater Horizon blowout may survive for longer than expected against the petroleum-eating microbes in the Gulf of Mexico, according to a new study.
Researchers took a “forensic snapshot” in late June that showed higher-than-expected oxygen levels in the plume from the oil well that began gushing in April. If microbes had swarmed into the area, their feeding frenzy should have reduced oxygen levels.
But the scientists said they have only just begun to analyze all the hydrocarbon molecules found in the oil plume, which typically serve as food for the microbes. They also cautioned that the study represented just one moment in time and space, and does not show what has happened to the plume since June.
“This was two weeks in June and a relatively small area in a very large body of water,” said Christopher Reddy, a marine geochemist at the Woods Hole Oceanographic Institute (WHOI) in Massachusetts, during a press conference on Thursday.
A monster of a plume
A research ship and its companion underwater robot tracked the oil plume out to at least 22 miles (35 kilometers) from the leaking oil well. Scientists aboard spent 10 days taking samples before the threat of Hurricane Alex forced them to break off.
“Unfortunately we were not able to track this out beyond 35 kilometers, although the data suggested that the plume extended for much farther than we tracked it,” said Richard Camilli, a chief WHOI scientist of applied ocean physics and engineering, and lead author on the study paper detailed in the Aug. 19 issue of the journal Science.
At the time, the plume stretched 1.2 miles (2 km) in width and reached 650 feet (198 meters) deep. The researchers found the plume was located more than 3,000 feet (914 m) below the surface of the Gulf of Mexico, holding stable at a depth of 1,100 (335 m) feet down.
Mass spectrometers aboard the robotic sub that were lowered from the ship allowed the team to begin fingerprinting the hydrocarbon molecules in the oil.
But the overall chemical analysis remains incomplete, and so the total amount of oil in the plume remains unknown. Questions about the possible hazards of the oil plume for marine life also remain up in the air.
“Without the complete picture of all the components of hydrocarbons, we can’t say much about its bioactivity or toxicity,” Camilli said.
The microbe buffet table
When the Deepwater Horizon rig first sank and unleashed an oil spill into the Gulf, experts had counted upon microbes to help break down the oil plumes. But the latest findings suggest that the microbes may feed slower than expected.
The plume also retained its massive size more than three months after the oil began gushing from the well.
Still, the results did not surprise David Valentine, a marine geochemist at the University of California, Santa Barbara who did not take part in the new study. He had participated in a separate expedition that found higher levels of microbial activity closer to the oil well.
Valentine pointed out that the new study has not yet analyzed many of the hydrocarbons in the oil plume. He added that the microbes might have quickly swarmed the leaking oil well area at first, but then slowed down in activity during the following months.
Furthermore, microbes probably break down certain hydrocarbons faster than others, Valentine said.
“I think we’ll find it’s a buffet [of hydrocarbons] down there,” Valentine told LiveScience. “The filet mignon may go quickly, but the taco bar will stay around for a while.”
The study’s researchers also gave their own warnings about drawing any premature conclusions.
“Microbes are a lot like teenagers,” Reddy said. “They work on their own time, their own scale, they do what they want when they want, and so it is often difficult to make predictions about microbe degradation, and in fact it may vary substantially in the Gulf in any one time.”
Lost and not yet found
The WHOI team hopes to also get a sense of what hydrocarbons have evaporated, and what has remained in the oil plume.
But first, researchers must relocate the oil plume again. That task of finding the missing plume has become harder since BP managed to temporarily cap the leaking oil well on the bottom of the Gulf.
“The faucet has been shut off,” Reddy acknowledged. “We don’t know where these hydrocarbons are, we saw them in June.”
The capping of the oil well means that researchers can no longer track the oil plume from its source, Valentine explained. “It’s a needle in a haystack problem,” Valentine said. “It’s a very large area, and it’s not a massive feature yet. But it will expand. Somebody will find it.”
Special thanks to Richard Charter