But with the Deepwater Horizon, they were. The day after the rig sank, BP sprayed 1,900 gallons of Corexit on the site. Within a week, it was dropping tens of thousands of gallons out of airplanes. Because the use of dispersants had been preapproved in BP's response plan, there was little oversight provided by federal health or safety agencies. As long as the chemicals were applied according to certain conditions – sprayed at least three miles off shore and in water at least 30 feet deep – there were no limits to how much could be used.
In the first weeks, BP discovered that dispersants did indeed help break up the oil slicks and drive the oil down into the water. But the chemicals also had another, more disturbing effect: They made the skimmers less effective. The best technology – known as an oleophilic, or oil-attracting, skimmer – uses mops or other absorbent materials to blot the oil out of the water. "Normally, the oleophilic skimmers should have been the backbone of our operation," says Mark Ploen, BP's offshore operations section chief at the command center. "But with all the dispersants being used, we found that less oil was sticking to the skimmers, and they were far less effective."
That meant the biggest skimmers in the Gulf, including a 174-foot-long, high-volume skimmer known as the HOSS barge, were of little use in the spill. It also meant that BP had to rely on a technology known as weir skimmers, which are placed just below the surface of the water, drawing both oil and water into a sump. But weir skimmers work best in thick, heavy oil spills; in the Gulf, where the oil was rising up from the seafloor and spreading out into a thin sheen, weir skimmers often picked up far more water than oil, making them troublesome and ineffective. By early July, with the cleanup effort undercut by chemical dispersants, BP was skimming up less than 1,000 barrels of oil a day.
But instead of dialing back on dispersants and deploying more skimmers, BP decided to wage chemical warfare in the Gulf. Within three weeks of the blowout, the company had dumped 300,000 gallons of Corexit into the ocean. By mid-July, the total had surpassed 1.8 million gallons. BP argued that dispersing the spill reduced the number of brown pelicans and sea turtles coated in oil, and prevented it from reaching fragile shorelines, where it is difficult to clean and deadly to breeding grounds for shrimp and other sea life. But the chemicals also benefited the company by effectively covering up the spill, breaking it up into thousands of smaller slicks that don't look so bad on the nightly news. "It's about PR," says Steiner, the scientist whose expertise helped contain the Valdez disaster. "It's about keeping the oil out of sight, and out of the public mind, so fewer people really understand what is happening in the Gulf and get outraged by it." During the Valdez response, he adds, Corexit earned a telling nickname: "Hides-it."
Whatever its motives, BP was slow to provide respirators to workers in the Gulf, leaving them exposed to a dangerous combination of oil and chemicals. Many complained of illnesses, headaches, nausea, and BP's own tests have shown that more than 15 percent of the response workers in the Gulf have been exposed to 2-butoxyethanol. "When oil goes into the water, nothing good happens," concedes Allen, the retired Coast Guard admiral overseeing the cleanup. "It's always a trade-off to try to minimize consequences."
Those consequences would be disastrous for the Gulf even if BP had refrained from using dispersants. Crude oil is poison to most living things. To make matters worse, the nasty chemical compounds in crude oil – benzene, toluene and heavy metals – don't stick together very long. Once oil blows out of a well and begins its hours-long journey to the surface, it undergoes a process that geologists call "fractionation," the heavier compounds drifting to the bottom of the ocean, the lighter compounds rising toward the surface. Where all these compounds go, and how they interact with living organisms in a complex ecosystem like the Gulf, is one of the great unknowns of oceanography.
One of the central factors in determining how oil moves is the loop current, which swirls around in the center of the Gulf like an underwater conveyor belt, transporting water in and out of the basin in a giant circle. "My initial fear was that this oil was going to get caught up in the loop current and moved right to the pristine beaches of Cuba and the Florida Keys, then up the coast as far north as North Carolina," says Rader, the chief ocean scientist for the Environmental Defense Fund. But a few weeks after the blowout occurred, an unexpected and fortunate thing happened: A large eddy developed in the Gulf, cutting off the current from the Florida Straits and keeping the oil largely contained in the Gulf itself. "We got lucky," Rader says.
The cutoff eddy lasted until late June. Now, however, it has separated into two eddies – which means the loop current could begin transporting the oil to more distant regions. But even if the oil remains in the Gulf, its effects on the environment could be felt thousands of miles away. Great migrations of fish visit the Gulf each spring and summer, using the waters as a spawning ground. "If they pass through the oil, billions of larvae and babies will be killed," says Rader. "It could have a large impact on populations outside the area."
The oil from the BP spill is not just swirling in the loop current. As it drifts up from the blowout site, it's also collecting in vast underwater plumes – some of them 10 miles long and three miles wide – composed of fractionated oil and methane. As bacteria begins to devour the oil in the plumes, they could leave behind huge swaths of water with little oxygen – massive dead zones that would suffocate any life within them. The plumes are also direct evidence that the oil is mixing at every level of the ocean, from the fragile coral reefs at the bottom of the Gulf to the shallower spawning grounds of the bluefin tuna. "The largest part of the Gulf ecosystem is out of sight beneath the surface," says Larry McKinney, executive director of the Harte Research Institute for Gulf of Mexico Studies at Texas A&M. "It's incredibly sensitive to the toxic effects of oil and dispersant."
As tragic as the images of dead seabirds are, scientists studying the environmental consequences of the Gulf spill are most concerned about the effects on the ecosystem that could take years to begin showing up. Scientists studying a spill off Cape Cod in 1969 are finding that 40 years later, fiddler crabs are still sluggish from the narcotic effects of oil. Studies after the Exxon Valdez spill in 1989 found that oil ingested by marine life accumulates in tissues, lowering reproductive rates and increasing disease and mortality rates. Oil continued to kill pink salmon eggs incubating in Alaskan streams for at least four years after the spill. As many as 700,000 seabirds died in the first few months, and sea otters and harlequin ducks suffered large, long-term losses. What's more, scientists found, the spill created a "cascade" of negative impacts up and down the food chain. The Pacific-herring population collapsed after the spill, and one pod of killer whales had its population cut by 40 percent. Two decades later, the whales are now doomed to extinction.
When you add dispersants to the mix, the environmental calculation gets even more complicated. Dispersants not only increase the amount of toxic chemicals in the Gulf, they spread the oil more widely – exposing far more plants and animals to a stew of hazardous compounds. "By breaking up oil slicks, you might reduce the number of acutely oiled pelicans and sea turtles," Rader points out. "But what about the rest of the food chain?" Observers in the Gulf have noticed what one environmentalist calls "drunk-dolphin syndrome" – pods of dolphins unusually close to shore, behaving in strange ways. "Is this a sign of environmental stress related to oil or dispersants?" says Ziccardi, the wildlife veterinarian. "We don't know." The same is true, he says, of the death of more than 450 endangered sea turtles: "It's a very high number that we can't explain yet."
The evidence of the disaster is most visible at the pelican rookeries of Barataria Bay. Cat Island, a tiny spit of land not far from Grand Isle, is teeming with birds – not just brown pelicans, but great egrets and roseate spoonbills. It is a Manhattan of birds, hundreds of them crowded together on a few hundred yards of mangroves, flapping, preening, basking in the sun. It's as if all the troubled birds in the bay have come here, seeking refuge, like animals fleeing a forest fire.
As it turns out, however, it was a foolish place to seek shelter. Barataria Bay has been hard hit by the spill, with oil moving in and out with the tides and the wind. Cat Island is surrounded by two rings of containment booms – but the concerted effort has failed to keep the oil away. The crude is thick among the mangrove trees, where it coats roughly half of the birds on the island. The oil doesn't look all that thick on their feathers – but that doesn't mean it won't do serious damage.
"We're not sure what the impact of this is going to be," says Melanie Driscoll, a bird-conservation director with the National Audubon Society. "We're definitely seeing more lightly oiled birds, which are more capable of escaping rescue attempts than heavily oiled birds. We're also seeing birds that are wet to the skin, which is unusual. There is some thought that the dispersants might be having an impact on their feathers, but we're not sure. Are these birds better off in the long run than the heavily oiled birds? We don't know. We don't know yet about their survival rate weeks or months from now, or about their reproductive capacity in the future. Frankly, there are just a huge number of unknowns here – and that's what concerns me."
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