Report: Nearly 80 Percent of Spilled Oil Still Threatens Gulf

Most of the oil spilled into the Gulf of Mexico earlier this year is still there and poses a sizable risk to the marine ecosystem, according to a report issued yesterday by a group of independent marine scientists. 

Of the 4.1 million barrels of oil spilled during the Deepwater Horizon disaster, the researchers estimate between 70 and 79 percent remains in the water. The new calculations are markedly different from a government report issued on Aug. 4 which argued that just 26 percent of the oil was "residual" in the water.

Media reports quickly picked up on this figure, and made it sound as though the vast majority of oil had simply disappeared. Jane Lubchenco, the head of the National Oceanic and Atmospheric Administration, appeared to be hedging her bets when she said, "At least 50 percent of the oil that was released is now completely gone from the system, and most of the remainder is degrading rapidly or is being removed from the beaches."

The new report, authored by a mix of oceanographers at the University of Georgia and the Skidaway Institute of Oceanography, called such characterizations "largely inaccurate and misleading."

The government numbers come from lumping in all of the oil released by the blown-out Macondo well, 4.9 million barrels, which includes some 800,000 barrels that never went into the gulf but were pumped directly from the well into container ships.

Working from a total estimate of 4.1 million barrels of oil in the water, the researchers found that government numbers still overestimate the amount of oil that has been broken down by organisms, sunlight and other natural processes. The government report estimated 16 percent of oil was degraded naturally, versus between 4 and 8 percent in the new report. 

What's more, the muck left behind is likely to be particularly toxic. From the new report:

The degradation of crude oil by marine organisms mostly entails short-chain hydrocarbons -- not the more toxic, polycyclic aromatic hydrocarbons (PAHs). [...] The most toxic components of crude oil are the least likely to be naturally degraded.

In the government version of things, dispersed and "dissolved or evaporated" oil make up nearly 50 percent of all the oil released by the blown-out well. The new report puts that figure at between 11 and 20 percent. 

There are a couple of reasons to believe this report, funded by the Gerogia Sea Grant, over the government's. First, it offers a range of possibilities, and its authors repeatedly state that they are uncertain about the quality of the data they are using, and what the different forms of oil will do to animals living in the gulf. Theirs is an estimate that, while not a finished product, at least tries to eliminate assumptions.

The government estimate, on the other hand, was backed by sweeping pronouncements from the White House press secretary:

White House press secretary Robert Gibbs said the report indicates the worst fears about the spill's potential impact won't materialize.

"I think it is fairly safe to say that because of the environmental effects of Mother Nature, the warm waters of the Gulf, and the federal response, that many of the doomsday scenarios that were talked about and repeated a lot have not and will not come to fruition because of that," Gibbs said during a news conference in Washington.

Second, and most importantly, it calls for more research. Finding large quantities of oil that have been dispersed into microscopic (but still toxic) droplets across much of the Gulf of Mexico is a difficult task at best, and simply put, no one has done it. Yes, there have been reports about underwater oil plumes. But good, solid scientific information has proven just as elusive as the oil itself.

In order to make a proper assessment as to what's going on in the gulf, much unglamorous, hard work remains to be done surveying the oil, measuring ocean currents, and testing wildlife for signs of contamination. Without that, as the researchers write, "it (will be) impossible to estimate how long it will take for oil to disappear from the Gulf."

Image: figure from report, Georgia Sea Grant (pdf)