Gulf Oil Spill a Slow-Motion Hurricane

By Janet Raloff, Science News

In a part of the world accustomed to the annual ritual of hurricane season, anticipating the landfall of oil from the Deepwater Horizon drilling platform that sank in the Gulf of Mexico April 22 has an eerie familiarity.

But unlike hurricane season, no one knows when this most recent threat to the marshes and estuaries of the Gulf Coast will end. Oil continues to gush unchecked from the seafloor site of the wrecked rig, some 40 miles off the Louisiana coast. It’s not clear how soon the well can be successfully capped, nor the magnitude of environmental threat posed by the river of oil that it’s spewing.

Best estimates indicate the well, which tapped a reservoir 13,000 feet below the seafloor, is pumping another 5,000 barrels — 210,000 gallons — of oil into Gulf waters daily. Several attempts to engage a shutoff valve at the seafloor have already failed. So within a week, British Petroleum, which had been leasing the Deepwater Horizon, hopes to effect a temporary fix: placement of a 125-ton containment dome over the largest source of oil (there are now several) from the wrecked rig.

A fact sheet prepared for the official Deepwater Horizon Joint Information Center, a collaborative enterprise run by the federal government and industry, claims this system “could collect as much as 85 percent of oil rising from the seafloor.” It also cautions, “This is the first time this system will be used at this water depth.”

“The only sure shot in getting this well under control is to drill another well and intersect the old well bore, then pump heavy mud and cement into it,” says Mike Miller, who heads Safety Boss, a Canadian oil field firefighting company. The technology to do that “is fairly certain.” But he echoed Gulf response teams when he said “it’s going to be months before that takes place.”

If oil releases continue at the present rate for another six weeks, Miller says, “there’s going to be more oil [spilled] than from the Exxon Valdez” — a tanker that ran aground in Alaska 21 years ago, releasing nearly 11 million gallons of oil. That accident has so far held the dubious distinction of being the nation’s biggest oil spill.

“We literally have just about a worst-case scenario,” says ecotoxicologist Ron Kendall, who directs the Institute of Environmental and Human Health at Texas Tech University in Lubbock. Occurring in spring, the new spill coincides with the time Gulf species are spawning or giving birth, he points out.

Spring is an especially bad time for a spill “because you’re starting the annual reproductive cycle [of area species],” says environmental chemist and fisheries biologist Jeff Short of Oceana, a marine conservation group. For nearly all species, the Juneau, Alaska-based scientist explains, “embryonic and juvenile life stages are most sensitive to oil.”

Spring is also when tropical storms are beginning to brew. Over the May 1 weekend, a storm system with sustained winds kicked up gusts of 30 miles per hour, Kendall noted. The weather made for choppy seas that hampered efforts to erect oil-containment booms along the ecologically fragile coastlines of Louisiana and Mississippi. Hurricane season officially begins July 1.

For University of New Orleans marsh ecologist Denise Reed, a primary concern is how these spring storms — and later, summer hurricanes — might aggravate oil’s intrusion into coastal areas. In calm weather, grasses at a marsh’s edge take the big hit as the first line of coastal defense — and frequently do just fine. Gooey oil may smother their lower leaves, but mature plants can send out replacements.

In stormy weather, however, that buffering cordon might be totally breached. Her worst-case scenario: “We get a small tropical system developing in the Gulf, a storm that’s not serious, usually.” But such events raise the water level all along the coast as an assault by waves — driven by perhaps 40 mile-per-hour intermittent winds — pushes water in. Instead of a few inches of water at the feet of wetland grasses, “the whole marsh would flood, leaving the grass covered with water for days,” Reed says. And that allows oil to ride over the marsh and further inland.

Ordinarily, the warmth of the Gulf and the teeming life within marsh soils will work to degrade oil, Reed observes. In those cases, she says, “doing nothing is a very viable solution,” because tramping in to remove oil would cause more harm than leaving the marsh to clean itself.

Unless there’s too much oil, Short says. The decomposition of organic matter — and crude oil is organic — can cause degrading microorganisms to use up all of the oxygen. This would smother most sediment-dwelling organisms. The oxygen deprivation would then “halt almost all oil degradation,” he says — which explains why coastal oiling “can be so persistent.” Indeed, he says, in marshy areas, trapped oil can last “up to a decade or more.”

It’s very hard to say when, where and how much oil will reach any particular part of the coast, says Ioannis Georgiou, a coastal oceanographer at the University of New Orleans.

The seabed’s topography and depth help determine the nature of local currents, their speeds and the degree to which water either stratifies or mixes. All are features that can play a big role in what happens to any oil that water transports. Unfortunately for spill-trajectory modelers, the last fairly complete bathymetry of the northern Gulf’s seafloor took place in 1927, he says.

Some patches of the Gulf’s seafloor have been periodically resurveyed since then. “I know,” Georgiou says, “because I do this work myself.” But the depth to the seafloor for most of the area over which the slick is predicted to travel has not been comprehensively mapped in more than 30 years, he notes — in many places for more than 70 years.

So coastal communities and scientists wait anxiously. As in the hours before a hurricane, they’re erecting barricades — in this case, floating booms to protect those nearshore and intertidal areas that Short calls the birthplace of the ocean. “You’d ideally want three or four layers of booms there” to backstop each other, he says. Their availability is being stretched thin, however, as coastal communities from Texas to Florida have been putting in requests for them.

But there’s one important way the current situation is much more frightening than the nervous hours before a hurricane, Reed notes. Hurricanes may be devastating, but “they’re a natural part of the system dynamic down here,” she observes. So the environment has learned how to recover from them.

“But oil,” she says, “this kind of insult is not something that these systems have seen before — certainly not on this scale. So their ability to cope with it has to be questioned.”

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