Giant plumes of crude oil mixed with methane are sweeping the ocean depths with devastating consequences. ‘I’m not too worried about oil on the surface,’ says one scientist. ‘It’s the things we don’t see that worry me the most.’
It was in mid-May that independent scientists — not any of the officials or researchers working for any of the government agencies on scene at the Deepwater Horizon disaster, let alone BP — first detected the vast underwater plumes of crude oil spreading like Medusa’s locks from the out-of-control gusher in the Gulf of Mexico. BP immediately dismissed the reports, and in late May CEO Tony Hayward flatly declared “there aren’t any plumes,” stopping just short of accusing the scientists of misconduct. Federal officials called the scientists’ claim “misleading, premature and, in some cases, inaccurate.” Moreover, continued a statement from the National Oceanic and Atmospheric Administration, any oxygen depletion in the surrounding waters due to plumes is not “a source of concern at this time,” and critics blaming dispersants for the plumes had “no information” to stand on. NOAA administrator Jane Lubchenco, a respected oceanographer when President Obama tapped her to lead the agency, insists there are no plumes, only “anomalies” — though last week she acknowledged the possibility of oil beneath the surface.
Now it is increasingly clear that the initial reports of undersea oil were right, that life-giving oxygen in the water column is indeed being depleted, and that unless the laws of chemistry have been repealed, dispersants are likely worsening the tentacles of undersea crude. What might have been just another oil spill — albeit a bad one — has been transformed into something unprecedented. Even if the containment dome lowered into place late last week continues to siphon off some of the leaking crude, the Deepwater Horizon disaster will enter the record books not for how much but for where: an enormous release of crude oil not only onto vulnerable shorelines and fragile marshes but into the largely unexplored depths of the sea. The consequences for the delicate balance of existence in the vulnerable ecosystems of the gulf, and for the vast cycles of nature that sustain life there and beyond, are as incalculable as they are potentially devastating.
“I’m not too worried about oil on the surface,” says chemist Ed Overton of Louisiana State University. “It’s going to cause very substantial and noticeable damage — marsh loss and coastal erosion and impact on fisheries, dead birds, dead turtles — but we’ll know what that is. It’s the things we don’t see that worry me the most. What happens if you wipe out all those jellyfish down there? We don’t know what their role is in the environment. But Mother Nature put them there for a reason,” and many are in the plumes’ paths.
Their presence has blown to smithereens the cliche that oil floats on water. That correctly describes what happens when pure crude spills into the sea from a well in shallow water or a tanker at the surface, as happened with the Exxon Valdez. But when a gusher is 5,000 feet down, consists of a mix of crude oil and dissolved methane, and is being disgorged under tremendous pressure and temperature, studies predict that the physical and chemical properties of the spill will undergo an ugly alchemy. “The dispersants are changing the chemistry and physics of the oil,” says biological oceanographer Ajit Subramaniam of Columbia University’s Lamont-Doherty Earth Observatory. “They are creating microlayers of oil that are being carried by the deep currents.” Even without dispersants, the crude gets broken into zillions of droplets suspended in the water column and corralled there, prevented from rising to the surface. The result is the undersea plumes that oceanographer Samantha Joye of the University of Georgia and colleagues first detected from the research vessel Pelican three weeks after the blowout. Despite years of research showing that undersea oil might form such plumes, BP’s Hayward insists it cannot. “Oil floats!” he repeatedly says.
Making matters more interesting, the chemical dispersants that work fairly well on surface spills, breaking apart oil slicks into droplets that degrade more quickly than a contiguous layer, may be exacerbating the undersea-oil problem. A 2007 report by the Minerals Management Service — which OK’s oil and gas leases — on the environmental consequences of oil and gas drilling on the outer continental shelf concluded that an underwater plume is a real possibility: “The use of dispersants on oil spills … could cause these compounds to reach the deeper water reef areas.” BP has pumped 185,000 gallons of dispersant onto the out-of-control wellhead (plus 800,000 on the surface). That is causing more of the gushing crude to break up into the very form unlikely to rise to the surface. There have been no suggestions that BP intended to keep the worst of the spill out of sight.
After NOAA questioned the finding of deepwater oil plumes (but now has two boats using sonar to look for plumes), the National Science Foundation stepped in with the kind of support that matters: cash. With “rapid response” grants from the foundation, scientists are searching for plumes and trying to assess their impact. As far as scientists can tell, the undersea oil is actually a witch’s brew of crude mixed with dissolved methane, stretching 15 miles long, 5 miles wide, and 300 feet thick in the case of one plume detected by the Pelican, and 22 miles long, 6 miles wide, and 3,000 feet thick in the case of a plume found by University of South Florida researchers aboard the Weather Bird II last week. The latter plume reaches all the way to the surface.
NOAA’s skepticism about plumes is correct on one point. Contrary to what the phrase conjures up, oil plumes are not black serpentines. The USF researchers caught one on camera last week, but in general they can be detected only by sophisticated instruments lowered into the depths. Samples hauled up do not even look black, though when they are run through a filter, black specks are revealed.
These undersea rivers of oil, though not nearly as concentrated as oil at the surface, are likely to affect the gulf through two mechanisms. The first is oxygen depletion, which has been estimated at 30 percent in the plumes. The other will be direct toxic effects of the oil and methane. Leatherback turtles and sperm whales dive to the 3,200-foot depths where plumes have now been detected, and aren’t smart enough to take evasive action. “They don’t necessarily recognize the plumes as something dangerous,” says marine scientist Ellycia Harrould-Kolieb, who works with the green group Oceana. Sharks, shrimp, and squid are all inhabitants of the deep, which would protect them from a Valdez-type spill on the surface, but now puts them in the crosshairs. Marlin, snapper, and grouper swim hundreds of feet down. One of the biggest losses may be bluefin tuna. Already imperiled from overfishing, the species breeds only in the Mediterranean Sea and the gulf. “This could spell the end to bluefin,” says Harrould-Kolieb. Even small bits of crude, like those in the plumes, can suffocate fish by gunking up their gills.
Other species imperiled by the deep-sea plumes include those that migrate down from the surface and others that make the reverse commute. “There are plankton that go from the surface to the middle of the water column, and other things eat them and go down deeper, and other things eat them and go to the bottom,” says oceanographer Lisa Levin of Scripps Institution of Oceanography. “All the zones of life interact, and now they’re probably all being hammered.”
The worst effect of large-scale death on the gulf floor is nothing as photogenic as dead pelicans, but much more pernicious. “The organisms most likely to be harmed by the oil plumes are those at the base of the food chain,” says biological oceanographer Andrew Juhl of Lamont-Doherty. “Most of the primary producers, such as phytoplankton, live throughout the water column. Effects on them would cascade to the larger species we care about.”
The deep-sea communities are also linchpins of the global carbon cycle — the ocean’s garbage men and recycling centers. They eat the waste and carcasses of creatures that lived and died in higher layers of the sea, and whose bodies drift to the sea floor. “The biggest biological component of the global carbon cycle is in the deep sea,” says marine biologist Jeffrey Baguley of the University of Nevada; without deep-sea organisms, dead marine creatures would accumulate like bottles and cans in places without deposit laws. That would deprive the rest of the living seas of the nutrients they need to keep life going. If a large enough area in the depths of the gulf becomes a kill zone, organic matter would accumulate in the sediment and be cut off from the rest of the ecosystem, says marine scientist Mahlon Kennicutt of Texas A&M.
Uniquely in the crosshairs are creatures living at or near the sea floor: deep-sea corals, jellyfish, and soft-bottom fish such as Atlantic croaker, sand seatrout, Atlantic bumper, sea robin, and sand perch. Three coral reefs live in the area under the surface slick, and two are close to one plume that scientists tracked last week. Oil could be lethal to a reef. The Minerals Management Service’s 2007 report concluded that “in the extremely unlikely event that oil from a subsurface spill were to reach a coral reef … in lethal concentrations,” recovery could take as long as “10-20 years.” “In the time scale of man, this will be a catastrophic event,” says Baguley.
Of special concern are the hundreds of “seep” communities in the gulf, enclaves of crustaceans, weird tube worms, tiny fish, mussels, and crabs that live near natural gashes in the sea floor. These seeps release hydrocarbons, which might suggest that the oil-and-methane plumes are good for these creatures. Unfortunately, the profusion of hydrocarbons is likely to be less like sitting down to a Thanksgiving feast than like being encased in marshmallowed sweet potatoes: deadly. Like Yellowstone’s geysers, they support unique organisms that may have scientific and commercial uses. Bacteria from a Yellowstone geyser are the source of enzymes that power a biochemical reaction called PCR, a workhorse of the genome revolution. Marine scientists have high hopes for finding similarly valuable microbes at the seeps. Some even talk of compounds that might fight cancer, much as extracts of the rosy periwinkle fight Hodgkin’s disease and childhood leukemias.
Oil on the ocean surface eventually evaporates, is degraded by sunlight, gets consumed by microbes, or washes up on beaches, where it can be collected. The fate and effects of the undersea oil are largely unknown. The Deepwater Horizon disaster is thus one big unplanned experiment. If the oil industry has its way — and with an estimated 30 billion barrels of crude-oil equivalent beneath the gulf’s ultra — deep (greater than 6,000 feet) waters, it’s hard to see how it won’t — we may have more such unplanned experiments. In 2008 Shell finished drilling an oil well 9,000 feet under the gulf, and BP has another well 7,000 feet down. The gulf has hundreds of other deepwater wells. In every case, the companies assured regulators, and the government agreed, that a deepwater accident that released oil onto the sea floor was exceedingly unlikely.
With Ian Yarett in New York and Daniel Stone in Washington.
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