This month, the federal government released a report on the fate of the 4.9 million bbl. of oil that spilled into the Gulf of Mexico after the Deepwater Horizon explosion. Experts from the National Oceanic and Atmospheric Administration (NOAA) and the Interior Department estimated that 74% of the oil had either been directly captured, burned or skimmed; evaporated at the surface; been consumed by micro-organisms; or dissolved or dispersed into microscopic droplets under the water.
That left just 26% of the original spill still present, either in sheen or in weathered tarballs, on the shore or buried in sediment. Though the report was preliminary and came with the necessary caveats, the message from the White House was clearer: the oil was disappearing and receding as a threat. "I think it's important to point out that at least 50% of the oil that was released is now completely gone from the system," said NOAA head Jane Lubchenco at an Aug. 4 White House press briefing. "And most of the remainder is degrading rapidly or is being removed from the beaches." That was good news for BP which hadn't had much in a while and just as good for right-wing bloggers and commentators like Rush Limbaugh, who had been claiming that greens exaggerated the disaster in order to boost the environmental cause.
But it turns out the high fives and told-you-sos might be premature. In a newly released report, researchers at the University of Georgia (UGA) looked at the government oil-budget survey and reached rather different conclusions. They believe that much of the oil the federal government viewed as dissolved or dispersed is still present underwater in the Gulf of Mexico, where its impact on aquatic life is far from clear. Nor is it well known how fast that underwater oil will continue to degrade or whether the chemicals the crude leaves behind as it breaks down could be dangerous in their own right. "The idea that some 75% of the oil is gone and not a threat to the environment is just absolutely incorrect," says Charles Hopkinson, director of Georgia Sea Grant at UGA.
The UGA scientists aren't the only ones calling the federal government's rosy picture of the oil spill into question. Another team of scientists, from the University of South Florida (USF), is releasing a report Aug. 17 showing that chemical dispersants may have caused a share of the oil to sink to the ocean floor, where some of it has been found at the bottom of an underwater canyon 40 miles (65 km) south of the Florida panhandle. That could have an effect on bottom-dwelling plankton that form the base of the marine food chain. The USF researchers also raise questions about the possibility that the sunken oil could float up again in the future.
But the scientists from UGA come at their work with special credentials. In early May, they were the first researchers to identify underwater plumes of oil forming from the BP gusher and they held on to that conclusion in the face of skepticism from the NOAA and BP, though government scientists later confirmed the existence of underwater plumes. So their take on Washington's oil-spill numbers gets special consideration. "The oil is still out there," says Hopkinson, "and will likely take years to completely degrade."
Here's how UGA tallied the oil-spill totals. First, the researchers discounted the 800,000 or so bbl. about 17% of the total amount spilled that were captured by BP at the wellhead, on the grounds that the oil never entered the Gulf. (The government report includes the 800,000 bbl., which somewhat inflates its numbers.) Of the remaining 4.1 million bbl., about 392,000 bbl. were either burned or skimmed from the surface, so that crude has been accounted for and is no longer part of the Gulf. But that leaves 90% of the total oil that actually made it into the water.
The federal government's happy report was based on the belief that everything but the residual oil that has reached shore was broken down enough by bacteria or some other mechanism that it no longer posed much of a threat. The UGA researchers, however, don't think such an assumption is justified. They had oceanographers and toxicologists from both UGA and elsewhere try to estimate how fast oil in the water would have broken down and concluded that as much as 80% of the 4.1 million bbl. of crude that spilled into the Gulf could still be present in the ecosystem in some form. "A large proportion of this oil is still in the system, floating around the water or trying to make it to the bottom," says Samantha Joye, a marine biologist at UGA. "Until we put a hard number on how fast the oil is degrading, we can't put a hard number on how much oil is still left."
Joye adds that the federal government hasn't taken into account the impact of all the methane that was released by the blown Macondo along with the oil. But it's important to realize that while we can't put hard numbers on how much oil is still out there, it's also hard to get a firm fix on the risks if any the remaining crude presents to the Gulf environment. These plumes aren't underwater rivers of oil they're likely invisible and represent mere parts per billion of oil in the water. "No one is saying it's all doom or gloom, but no one here is saying the oil is all gone either," says Joye, who will be part of a new UGA expedition to the Gulf leaving later this week. "We're trying to point out that for this system, the impact of the oil is there."
This all means that we need many more studies and we need them from multiple sources, because as long as the cleanup remains and the legal issues from the spill are still in the air, the Gulf is effectively a crime scene. That's why Greenpeace has launched a two-month-long expedition to the Gulf, giving scientists from a variety of universities the chance to use its Arctic Sunrise ship as a base for marine experiments. I'm with them now for the first leg, in the Dry Tortugas, west of the Florida Keys. This gorgeous collection of coral reefs and uninhabited islands was fortunate enough to miss the biggest impacts from the spill, but it's right next door to the Gulf. "Dispersed oil doesn't mean the oil is gone," says John Hocevar, Greenpeace's oceans campaigner. The summer of the spill may be winding down, but this battle isn't over.