Gulf of Mexico

Where Has All the Oil gone?

Recently, several apparently conflicting reports have addressed questions about the amount of oil remaining in the ocean following the BP Deepwater Horizon disaster, and about the presence of subsurface "plumes" of oil. The varying assessments and news media coverage have caused some confusion, and may have created a false sense that the oil that spilled into the Gulf no longer poses a threat to the ecosystem.

While capping the well was the necessary first step on the road to recovery, we cannot gloss over the fact that a significant amount of oil remains in the ocean. An estimated 4.9 million barrels of oil were released, making the Deepwater Horizon disaster the largest accidental release of oil into the ocean in history. By any measure, an astonishing amount of that oil likely remains in the environment.

A recent report from the National Oceanic and Atmospheric Administration (NOAA) suggested that much of the spilled oil has evaporated, dissolved, or been removed from the ecosystem by responders However, that same report estimated that more than 100 million gallons of oil remained - the equivalent of the oil released from more than nine Exxon Valdez spills.

Another independent study estimated that up to 79 percent of the oil--as much as 134 million gallons--remained in the environment.

Scientists at Woods Hole Oceanographic Institution conducted field research documenting the presence of subsurface oil "plumes" in June and recently published their findings. Another study, however, this one by scientists at the Lawrence Berkeley National Laboratory, concluded that the plumes have now disappeared.

In looking at these several reports as a group, it is important to remember that the Gulf of Mexico is a very large place and these studies were conducted at different times. Not only is the task of documenting the fate and effects of oil from the BP disaster very complicated, requiring sophisticated science; it is also not likely that any one study will provide definitive answers.

For Ocean Conservancy, the bottom line is that a large amount of oil likely remains in the environment, but we also recognize that the amount of oil remaining in the Gulf is decreasing as physical degradation and digestion by microbes break down some of the oil into harmless forms.

It may take years to fully assess the ecological damage already done by the oil disaster, and it may take decades to fully restore the ecosystem. There is potential for lingering oil—especially buried in sediments—to remain in the environment well into the future. Ocean Conservancy is working both on the ground in the Gulf and in Washington, DC, to ensure that a transparent, science-based damage assessment is conducted, and that a comprehensive restoration plan is put in place. We believe that is the best way to achieve a healthy Gulf ecosystem—for this and future generations.

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