Putting A Lid on the Truth: Underwater Oil Plumes. The Oil Spill is far worse than the Surface Slick would suggest.

by Jim White

Global Research, May 20, 2010

On Saturday, the New York Times brought the world’s attention to the discovery by a team of researchers on the the vessel Pelican that there are large underwater plumes of oil see THIS... emanating from the Deepwater Horizon spill. Remarkably, the response of the government to the attention focused on this discovery has been to tell the researchers to stop granting interviews with the press. At the same time, the blog on which the researchers had been providing updates has also fallen silent since Saturday. (Editor's NOTE: For background see THIS...

Pensacola television station WEAR filed a report on the oil plume and broke the news about the scientists being muzzled by the government:

Over the weekend, a research crew from the University of Southern Mississippi found evidence that there are 3 to 5 plumes… About 5 miles wide, 10 miles long and 3 hundred feet in depth.

But after giving that information to the press, the lead researcher now says he has been asked by the federal government… Which funds his research… To quit giving interviews until further testing is done.

What an interesting change of course for the government. Even the government’s website on the Deepwater Horizon response had been touting the mission of the Pelican as recently as May 6:

The university fleet research vessel Pelican, operated by the Louisiana Universities Marine Consortium, departed Cocodrie, La., late Tuesday and arrived at the spill source on Wednesday. They will return on Sunday for more supplies, and go back to the site later that week.

The ship had been outfitted and ready to support a different NOAA-funded mission, but it was scrubbed in favor of gathering timely and much-needed data close to the oil spill source.

“This sampling mission is one of many NOAA responses to the oil spill,” acting NOAA assistant administrator for NOAA Research Craig McLean said. “It fills an important gap in researching the interaction of spilled oil and the ocean environment. The samples will help us better understand affected ocean resources.”

“We plan to sample as close to the well head as is safe, reasonable and allowable,” said Ray Highsmith, executive director for NIUST and principal investigator for both the original and revised mission. “We then plan to travel northwestward toward our long-term study site.”
The question now becomes whether the government, in the form of NOAA (which sponsored the research) is merely asking for a pause in order to process data more fully, or if it is putting the lid on a story that shows the oil spill to be far worse than the surface slick would suggest. One way to judge the answer to that question will be to see how quickly the research team is able to find ship time for gathering more data. Here is one of the researchers, Dr. Vernon Asper, speaking with NPR on May 16 with interviewer Guy Raz (in the only post-May 15 interview I’ve been able to find for any of the researchers):

RAZ: Vernon Asper, what will you and the scientists aboard the Pelican be looking at in the coming days and weeks?

Dr. ASPER: The first thing we’re going to do is analyze our data and analyze the samples. And, of course, we’re planning our next cruises. We’re already making inquiries into finding ship time. It turns out that the limiting factor for studying this plume is the availability of research vessels.

The research fleet in the United States for academic purposes has been dwindling over the last few decades, and there just aren’t ships available. So we’re having a hard time getting access to vessels that can take us out there.

If the US government, acting through NOAA, is truly interested in understanding the extent of underwater oil plumes emanating from the Deepwater Horizon spill, then they will be able to arrange access for this team to gather more data aboard the Pelican or another research vessel very soon. On the other hand, if the desire of the government is to divert attention from what could be very disturbing results, then somehow this team just won’t be able to find ship time in the next few months. (Editor's bold emphasis throughout).

In the meantime, we have the first report of tar balls washing ashore in Key West. The material will be analyzed, and if the profile matches the material from the spill, then we will have confirmation that the oil has entered the loop current. Since we don’t see surface oil that far south, how could that oil reach Key West? Perhaps traveling as a plume under the surface?


Editor's NOTE: The following article by researcher Samantha Joye from almost 2 weeks ago provides valuable background information on the oil plumes.

Hide and seek
Gulf Oil Blog
By Samantha Joye | Published: June 6, 2010 12:17am

June 5th, 18:34. The plume was hiding. We anticipated that the flow trajectory of the oil and gas discharging from the leaking riser pipe would change after the pipe was cut but it was tough to predict which way the flow would go. We had a day and a half of ops remaining and our goal was to find the plume, revisit several stations to see how they had changed over time, and sample two control sites well away from the plume.

When we arrived back at ground zero, things had changed. The Discoverer Enterprise was sporting a methane flare. This is how drilling ships and rigs get rid of excess methane gas—they burn it.

The flare was visible from several miles away and when we were up close, about 0.75 miles away, the roar of the flame was audible. Several fire control boats were dousing the flare pipe and the area around it with water to keep it as cool as possible. The sound of the burning flame was mesmerizing and we spent some time taking in the sight.

We found the plume after about 8 (very frustrating) hours of searching for it. The weather was windy and rainy; the seas were unsettled; visibility was limited. The Discoverer Enterprise was about 1.5 miles away from us but you could barely see it through the rain. The dreary conditions mirrored how I felt after spending 8 hours trying to find something I knew was there. I thought the plume had moved to the east but it turned out that it had moved south. So much for intuition!

In the end, all was well because we found it. We wanted to have plume samples after the riser was cut so we could compare them to those collected before it was cut. We collected samples of the plume waters near the spill site and of the waters above and below the plume. Then, we moved on to re-occupy some stations we visited during our first three days of operations with the goal of determining how things had changed over a week.

We have three stations remaining to sample and will head back to Gulfport about 10PM this evening. We should be in tomorrow afternoon. During this cruise, we sampled 79 stations and conducted 89 CTD casts. Over the coming weeks, we’ll be analyzing samples, running lab experiments and pulling all the data together to see what stories they tell.

Below, I’ll do my best to answer some of the questions I have received in the past few days. The questions are in bold (I’ve shortened some of them); my answers are in regular font.

Is the oil/dispersant mixture in micellar form? Or is the oil in droplets?

The answer is both. It’s likely that some of the oil-dispersant mixture is present as micelles but there are also oil droplets in some of the samples, especially those from near the leaking riser pipe. There is a lot of light scattering in the plumes, this could be due to several factors, including the presence of oil in the water.

Re: sulfonate detergent micelles: what effect does this ionic packaging have on accessibility to the oil of bacteria doing the bioremediation?

Unfortunately, no one knows the answer to this question and it is a KEY question that we need to know the answer to.

Iron depletion appears to be a limiting factor in growth of algae in seawater. Is it known whether this, or some other limitation, will restrict bacterial degradation of the oil?

Oddly enough, there could be a good bit of iron coming out of this leaking well. We have not measured total Fe (Iron) content but others have told me that there is a lot of iron [Fe(III)] in the water. So, iron concentrations could be elevated around the spill site.

Why can’t they implode the well like they did during the Gulf War?

That is not really an option in this situation. This reservoir is extremely methane rich and detonating a blast would lead to major destruction and destabilization of a significant area of the slope in the vicinity of MC252. In my opinion, this option is far too dangerous to be seriously considered.

How serious is the oxygen depletion problem?

Potentially, this is a very serious problem. At present, oxygen concentrations exceed 2 mg/L but if concentrations drop below that, it would spell problems for any oxygen requiring organisms. The Southwest Plume is, at a minimum, 15 miles long x 2 miles long and the plume is about 600 feet thick. Temperatures in the plume are about 8-12ºC. We do not know the absolute oil content at this time.

The plume is largely water. This is not thick oil like you see on the surface in some places, it’s diluted oil and it’s most concentrated closest to the leaking riser pipe. Unlike a natural oil seep, which is most intense on the bottom and whose signal decreases with depth above the seafloor, the plume we are studying starts 200m above the seafloor and its intensity decreases horizontally with distance away from the leaking wellhead.

The specific gravity of oil is irrelevant to this discussion. This is not oil like you buy at the auto supply store. Think of it as gas-saturated oil that has been shot out of a deep sea cannon under intense pressure – it’s like putting olive oil in a spray can, pressurizing it and pushing the spray button. What comes out when you push that button? A mist of olive oil. This well is leaking a mist of oil that is settling out in the deep sea.

How much biodegredation appears to being observed for the oil plumes?

There is a tremendous amount of oxygen consumption in the plumes. We have measured respiration rates in the plumes, above and below the plumes, and at control sites where plumes are not present. The respiration rates in the plume are at least 5-10 times higher than we see anywhere else.

Are the conditions good for the microbes that can degrade these types of hydrocarbons?

Right now, conditions seem to be ideal for microbial degradation. But we need to do additional lab experiments to figure out what is regulating microbial activity.

Are the concentrations of the hydrocarbons so great that the microbes are overwhelmed or killed?

We have not yet measured toxicity but we plan to do that when we get back to the lab at UGA.


UGA expert describes a spill like no other

By Lee Shearer
Onlineathens.com
Published Wednesday, June 09, 2010

Nothing like the oil spill in the Gulf of Mexico has ever happened before - at least not in human history - and it will take years for scientists to understand the damage it causes, University of Georgia marine scientist Samantha Joye said Tuesday.

"It's an imbalance in the system, and that's the danger. You've pushed it to a much more unstable condition," Joye said during a news briefing in the Georgia Center for Continuing Education.

Even the unprecedented infusion of millions of gallons of oil and methane gas probably won't turn the Gulf into a completely dead zone, said Joye, who returned Sunday from a two-week ocean-going research expedition to map and analyze one of the giant plumes that have formed underwater as oil, methane gas and other chemicals spew from a broken oil well a mile below the surface.

The scientists found that oxygen is severely depleted even in water far from the spill - creating conditions close to so-called dead zones, where fish and other marine creatures can't breathe because of the lack of dissolved oxygen in the water.

Bacteria breaking down the methane and other hydrocarbon chemicals in the oil consume the oxygen, Joye explained. But a lack of other nutrients such as nitrogen will likely limit the bacteria's ability to reproduce and use up the remaining oxygen.

Oil has spread for miles along the Gulf Coast since the drilling rig Deepwater Horizon blew up April 20, killing 11 workers and causing the well to spew petroleum uncontrollably. The oil now is washing ashore, killing marine birds, mammals and other animals, and fouling beaches.

Scientists fear the ecological damage could be worse from the oil hidden underwater than the slicks of oil visible at the surface.

Researchers first discovered the plumes in early May, but federal officials only Tuesday confirmed their existence. Officials with BP, the company responsible for the spill, said last week the plumes don't exist.

The plumes are not just oil, but a mixture of oil, methane and other organic chemicals suspended in sea water.

Joye's team measured methane levels in some places at 10,000 times what normal ocean water would contain.

"I've never seen methane concentration this high anywhere in the water," she said.

The oil is likely to slosh around in the Gulf of Mexico for a long time, swirled around by ocean currents, she said.

"It's not a closed body of water, but it's an isolated body of water," she said.

Chemical dispersant's added by BP have helped keep oil underwater.

"The whole goal of adding dispersant's (in deep water) was to keep the oil under water, which seems to be working," she said.

But much would have remained underwater anyway - and some of it could stay there a long time, too, Joye said. The mixing rate - the time it takes for bottom water to reach the surface and vice versa -in the Gulf is about 175 years, she said.

Scientists don't know how the spill and the drifting plumes will affect the web of life in the ocean, said Joye. They also don't know what the effects of the chemical dispersant's, will be, though the chemicals are banned as toxic in some countries.

Joye's research team found some evidence that some kinds of life are being suppressed. Small creatures called phytoplankton, a crucial link in the oceanic food web, usually proliferate at this time of year. But the depressed oxygen levels the scientists found indicate the blooms are not happening this year, she said.

Joye, a UGA faculty member since 1997, will recommend in hearings before Congress today that a blue-ribbon National Academy of Sciences panel investigate the consequences of the spill.

An estimated 50 million gallons or more has spewed into the Gulf since the rig sank, two days after the fatal explosion. Federal officials say the oil flow could continue into the fall.


SCIENTIST AWED BY SIZE, DENSITY OF UNDERSEA OIL PLUME IN GULF
By Paul Quinlan and Josh Vorhees of Greenwire
New York Times
June 9, 2010 (posted Jun. 8)

Vast underwater concentrations of oil sprawling for miles in the Gulf of Mexico from the damaged, crude-belching BP PLC well are unprecedented in "human history" and threaten to wreak havoc on marine life, a team of scientists said today, a finding confirmed for the first time by federal officials.

Researchers aboard the F.G. Walton Smith vessel briefed reporters on a two-week cruise in which they traced an underwater oil plume 15 miles wide, 3 miles long and about 600 feet thick. The plume's core is 1,100 to 1,300 meters below the surface, they said.

"It's an infusion of oil and gas unlike anything else that has ever been seen anywhere, certainly in human history," said Samantha Joye of the University of Georgia, the expedition leader.

Bacteria are breaking down the oil's hydrocarbons in a massive, microorganism feeding frenzy that has sent oxygen levels plunging close to what is considered "dead zone" conditions, at which most marine life are smothered for a lack of dissolved oxygen.

Such low-oxygen conditions were noticed farther from the spill site, although Joye said she did not think the process would immediately produce a dead zone, since low nutrient concentrations in the water would limit the rate of the bacterial consumption.

Joye said her team also measured extremely high levels of methane, which is also spewing from the gushing BP well at up to 10,000 times background levels in Gulf waters.

"I've been working in the Gulf of Mexico for 15 years," Joye said. "I've never seen methane concentration this high anywhere in the water."

Less clear to researchers like Joye are what role the unprecedented deployment of oil-dispersing chemicals are having on the undersea gathering of oil. She said dispersant's likely played a role in keeping the oil underwater but that they are "certainly not required" to produce such an effect, given the deep-water -- as opposed to surface -- injection of oil and gas.

Also still unclear, she said, are the long-term effects of oil and dispersant use on fisheries.

"The primary producers -- the base of the food web in the ocean -- is going to be altered. There's no doubt about that," Joye said. "We have no idea what dispersant's are going to do to microorganisms. We know they are toxic to many larvae. It's impossible to know what the impacts are going to be."

A full understanding and the full impact to the Gulf's fishery may be years away, she said.
"It's a very, very complicated problem, and there are a lot of people doing fisheries work to try to get a handle on this, but it's going to be months or years probably before we realize the full consequences of this spill," Joye said.

Asked to react to BP officials earlier assertions that the Gulf of Mexico was a large enough body of water to absorb the impact of an oil spill under way, Joye bristled.

"The solution to pollution is not dilution," she said. "It's an excuse, and it's arm-waving, and it takes away from the important things that we should be thinking about," she said, such as measuring the scope of the spill and its effects.

FEDERAL CONFIRMATION

Federal officials for the first time today confirmed the researchers' findings, although Coast Guard Adm. Thad Allen, who is leading the federal response to the spill, questioned the use of the term "plume" to describe that underwater oil.

"The term 'plume' has been used for quite awhile, [but] I think what we are talking about are concentrations," he said. "'Cloud' is a better term."

Joye's team's results echo the findings of a University of South Florida team aboard the Weatherbird II vessel.

National Oceanic and Atmospheric Administration chief Jane Lubchenco said her agency had finished testing water samples collected by the USF team that confirmed the presence of the oil.

"The bottom line is, yes there is oil in the water columns," she told reporters. "That's confirmed for the sites we've done the analyses."

BP CEO Tony Hayward had disputed the presence of plumes, saying on June 6 that there was "no evidence" of their existence. BP spokesman John Pack said today they would be paying attention to the data that is coming in.

"We will obviously listen to what they have to say," Pack said.

Lubchenco said the test confirms the presence of subsurface oil, which she said federal scientists suspected was present.

Lubchenco said that oil was found in "very low concentrations" in the range of less than 0.5 parts per million. NOAA tested samples from three collection sites, confirming the presence of subsea oil 40 nautical miles northeast of the well. She said samples from a site 42 nautical miles northeast were inconclusive and that samples from a site 142 miles southeast "were not consistent with the oil spill."

"That does not mean it doesn't have significant impact. A more complete picture will require additional information, and we're in the process of getting that," Lubchenco said.

"We remain concerned about the location of oil on the surface and under the sea," Lubchenco said. "We are attacking it aggressively to mitigate the harm and understand the impact."

Lubchenco said "there is definitely oil subsurface" and that NOAA would continue to analyze water samples as they were collected.

"We will continue to do research to understand where it is and in what concentrations and what are its impacts," she said.

Gulf Oil Disaster: A Transatlantic Pollution Catastrophe Looms

by Finian Cunningham
Global Research, May 21, 2010

The Gulf of Mexico oil spill disaster threatening to wipe out tourism and fishing industries and countless numbers of marine wildlife habitats along the entire US southeast coast could be just the prelude to a much greater transatlantic pollution catastrophe.

The furthest eastern state of Florida – 600 miles from the Deepwater Horizon spill site off Louisiana – is next at risk to devastating pollution as a result of giant undersea oil plumes being swept up by fast-moving Caribbean currents known as the Gulf Loop. But US government officials are now warning neigbouring countries to also prepare for contamination. Indeed, the US state department has taken the highly unusual step of contacting the Cuban government to warn it of the pollution risk.

With efforts to curtail the flow of oil gushing from the seabed well by British Petroleum proving ineffective a month after the explosion on an exploratory rig, it is feared by several marine scientists and engineers based in the region that the spill could reach up to a total of six million barrels of crude oil equivalent – 25 times greater than the 1989 Exxon Valdez incident off Alaska, which up to this was considered one of the worst human-made environmental disasters.

With up to 70,000 barrels of oil spewing into the Caribbean every day, there are well-founded fears that the Gulf Loop will pass on its contamination load to the Gulf Stream which, in turn, pours into the North Atlantic. If this happens then the countries of Western Europe that are bathed by this giant oceanic current will also suffer the hydrocarbon toxic fallout from the Deepwater Horizon, scientists say. The multibillion-dollar damage to communities, industries and the incalculable ecological cost might then be multiplied to trillions.

And the full extent of this transatlantic catastrophe does not even stop there. In the South Atlantic, the offshore territories off West Africa – including those of Ghana, Ivory Coast and Sierra Leone – have in recent years become major players in global oil exploration. Since discoveries of huge undersea oil reserves in 2007 off Ghana, in particular, international oil companies, including Exxon and Russian and Chinese state-owned firms, have been flocking to the West African country eager to exploit its newfound natural wealth. More than 50 international oil companies are vying for this equatorial oil bounty, according to the Ghanaian energy ministry.

One of Ghana’s major offshore oil prizes is the Jubilee Field, which is estimated to contain reserves equivalent to 1.8 billion barrels (1,800 million barrels). Production from oilrigs off this former British colony is scheduled to begin later this year – for the first time.

Of concern is that Transocean – the operator and owner of the Deepwater Horizon rig contracted by BP – is also the major operator in Ghana’s nascent offshore industry. The New York and Zurich-listed company is the world’s biggest such operator, with over 300 rigs worldwide, according to its website. The company views West Africa as one of its growth areas. [1]

It is now well documented in the case of the Gulf oil spill, which resulted from an explosion on 20 April on Transocean’s Deepwater Horizon rig claiming the lives of 11 workers, that the disaster stemmed from negligence in safety standards and procedures carried out by Transocean. The two main safety shortcomings were the faulty method by which the rig tried to shut off the exploratory wellhead and the failure of a blow-out valve to activate in order to seal the resulting gusher. Not only that, but these systemic dangers in the company’s drilling operations were highlighted over several years by independent engineers and consultants. Both US government officials and the oil industry ignored the warnings, evidently in a rush to maximise profits. [2]

This revolving door relationship between the US government and the oil industry whereby a blind eye was turned on safety regulations, in particular those of Transocean, raise deeply troubling concerns about the risk of an equally disastrous oil spill in the newly opened West African offshore fields.

Sam Danse, who is Oxfam’s country director for Ghana, told BBC World Service (19 May) that he fears international oil companies are using their colossal economic strength to ride roughshod over West African government officials and safety regulations. He cited Transocean in particular with regard to Ghana.

Transocean’s annual profits of over $4 billion is more than a quarter of Ghana’s gross domestic product and approximately the same as the country’s total debt. That is a lot of leverage on a government of a poor country desperate to get its oil industry up and running as quickly as possible. As Danse pointed out: “If that’s what this company got away with with American industry regulators, what can it get away with those in Ghana?”To make matters worse, Ghana has already an unenviable reputation for endemic government corruption. The World Bank’s Ease of Doing Business (2010) ranks the country 92nd out of a total of 183. Ordinary Ghanaians often complain that their government ministries are “in the pockets” of foreign investors. Former British deputy high commissioner Craig Murray, who fell foul of his own government in the late 1990s for blowing the whistle on bribery and fraud involving British companies in Ghana, says that the country’s energy sector is particularly prone to corruption.

“The truth is that sadly there was a major increase in corruption in Ghana especially in 2007 and 2008. That was a major reason why the Ghanaian people voted to change their government. But so far there is little indication that the new government has done much to root out the corruption,” says Murray.

If the level of corruption that has been shown in the Gulf of Mexico oil industry is replicated in West Africa’s inexperienced offshore enterprises, then this opens up the possibility of a ticking bomb for a similar oil spill disaster occurring in the South Atlantic. Given that this oceanic region off West Africa drives major ocean currents back to the Americas in a manner countercyclical to the Gulf Stream in the North Atlantic [3] this opens up an appalling vista of a transatlantic triangular catastrophe in oil pollution.

Notes

1. http://www.businessweek.com/news/2010-03-22/transocean-has-25-of-fleet-standing-by-in-shipyards-update3-.html

2. http://www.wsws.org/articles/2010/may2010/spil-m14.shtml


3. http://en.wikipedia.org/wiki/Atlantic_Ocean

Gulf oil spill plume to cause dead zones for Florida animals, wildlife

May 20, 2:28 PM
Maryann Tobin
Examiner.com, Louisville

Scientists are deeply concerned about a massive oil plume which has been picked up by the Gulf current, and is expected to reach Florida within 10 days. The path will take the plume past the waters off Tampa Bay. It is predicted to cause massive dead zones where nothing can survive.

Since the Deepwater Horizon exploded on April 20th, 2010, estimates vary on just how much oil, gas and chemicals have been dumped into the Gulf of Mexico. Worst case scenario's put the total at more than 100 million gallons, and the leak has still not been stopped.

More than 45 thousand square miles of fishing waters have been closed since the onset of the BP disaster a month ago. In that time, the corpses of dolphins, turtles, birds and fish have washed up on Gulf coast shores.

BP Managing Director Bob Dudley admitted that the oil spill has “hurt Florida.” However, he played-down the deadly consequences to the animals that call the oily water home.

Senator Bob Menendez (D-NJ) called it “A man made disaster made by BP,” in an MSNBC interview today.

Dolphins often spotted off the shores of Tampa Bay feed in deeper Gulf waters. The oil and chemicals that threaten to form dead zones may cause the intelligent, social mammals to die of starvation or poisoning. (Editor's bold emphasis throughout)

BP admits more oil is spilling into Gulf than estimated

Oil impacted marshes are seen in Loutre, La. on Wednesday, May 19, 2010. Oil from the Deepwater Horizon oil spill is infiltrating the coast of Louisiana. BP has said more oil has leaked into the Gulf of Mexico than originally projected.

By Associated Press / May 20, 2010
New Orleans, Louisiana

BP conceded Thursday that more oil than it estimated is gushing into the Gulf of Mexico as heavy crude washed into Louisiana's wetlands for the first time, feeding worries and uncertainty about the massive monthlong spill.

Mark Proegler, a spokesman for oil giant BP PLC, said a mile-long tube inserted into a leaking pipe over the weekend is capturing 210,000 gallons a day — the total amount the company and the Coast Guard have estimated is gushing into the sea — but some is still escaping. He would not say how much.

Several professors who have watched video of the leak have said they believe the amount spewing out is much higher than official estimates.

Proegler said the 210,000 gallons — 5,000 barrels — has always been just an estimate because there is no way to measure how much is spilling from the seafloor.

"I would encourage people to take a look at the changing amount of oil coming from the ocean floor," said Steve Rinehart, another BP spokesman. "It's pretty clear that now that we're taking 5,000 barrels of oil a day, there's a significant change in the flow reaching the sea."

A live video feed of the leak posted online Thursday at the insistence of U.S. Rep. Edward J. Markey, D-Mass., shows what appears to be a large plume of oil and gas still spewing next to the tube that's carrying some of it to the surface.

The well blew out after an explosion a month ago on the offshore drilling rig Deepwater Horizon that killed 11 people. At least 6 million gallons have spilled so far, making it the worst U.S. environmental disaster in decades. The Exxon Valdez tanker spilled 11 million gallons in Alaska in 1989.
(Editor's emphasis)
Small amounts of light oil have washed up in delicate coastal areas of Louisiana over the past several weeks, but nothing like the brown ooze from the spill that started coating marsh grasses and hanging in the shallow water of a wetland Wednesday.

"This is the heavy oil that everyone's been fearing that is here now," Gov. Bobby Jindal said during a boat tour Wednesday in southeastern Louisiana. The wetlands at the mouth of the Mississippi River are home to rare birds, mammals and a wide variety of marine life.

Much of southeast Louisiana's coastal waters have been closed to fishing and oyster harvesting because of the oil. A vast area stretching east toward Florida in federal waters also has been closed to seafood harvesting.

Officials in Florida sought to reassure tourists that the state's beaches are clean and safe as government scientists said a small portion of the slick had entered the so-called loop current, a stream of fast-moving water that circulates around the Gulf before bending around Florida and up the Atlantic coast.

During a news conference, David Halstead, director of the Florida Division of Emergency Management, showed off a picture of a Coppertone bottle on a beach.

"What's the only oil on the beaches? Suntan oil," he said.

Tracking the unpredictable spill and the complex loop current is a challenge for scientists, said Charlie Henry, a NOAA environmental scientist.

The loop moves based on shifting winds and other environmental factors, so even though oil is leaking continuously it may be in the current one day, and out the next. The slick itself has defied scientists' efforts to track it and predict its path. Instead, it has repeatedly advanced and retreated, an ominous, shape-shifting mass in the Gulf, with vast underwater lobes extending outward.

Florida's state meteorologist said it will be at least another seven days before the oil reaches waters west of the Florida Keys. U.S. officials were also talking to Cuba about how to respond to the spill should it reach the island's northern coast, a U.S. State Department spokesman said.

BP, which was leasing the rig when it exploded, was marshaling equipment and conducting tests Thursday ahead of a new effort to choke off the oil flow. Crews hoped that by Sunday they can start a procedure known as a "top kill," which involves pumping heavy mud into the crippled equipment on top of the well, then permanently sealing it with cement.

The procedure has been used before to halt gushing oil above ground, but like other methods BP is exploring it has never been used 5,000 feet below the sea. That's why scientists and engineers have spent much of the past week preparing and taking a series of measurements to make sure the mission doesn't backfire.

"The philosophy from the beginning is not to take any action which could make the situation worse, and those are the final steps we're doing," said Doug Suttles, BP's chief operating officer.

Anger over the spill has mounted as the efforts to stop the leak have dragged on. Greenpeace activists scaled BP's London headquarters Thursday to hang a flag accusing the oil company of polluting the environment. The group said the action was prompted by the Gulf of Mexico oil spill as well as a controversial project in Canada.

"It takes some cheek to go and use a sunflower logo when your business is dirty oil," Greenpeace activist Ben Stewart said from a balcony above the headquarters' front door in a telephone interview.

BP spokesman Robert Wine called the action "a very calm and genteel protest," and said no employees had been prevented from getting to work.