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The BP oil saga may have been laying low in the media recently, but a new report sheds a disturbing light on the ongoing environmental impacts of the spill. According to the report, released by the Georgia Sea Grant and the University of Georgia, up to 79 percent of the oil released into the Gulf of Mexico from the Deepwater Horizon well has not been recovered and remains a threat to the ecosystem.

The marine scientist-authored report strongly contradicts media reports that suggest that only 25 percent of the oil from the Deepwater Horizon oil spill remains.

“One major misconception is that oil that has dissolved into water is gone and is therefore harmless,” says Charles Hopkinson, director of Georgia Sea Grant and professor of marine sciences in the University of Georgia Franklin College of Arts and Sciences. “The oil is still out there, and it will likely take years to completely degrade. We are still far from a complete understanding of what its impacts are.”

Authors of the report analysed data from the Aug. 2 National Incident Command (NIC) Report, which calculated an “oil budget” that was widely interpreted to suggest that only 25 percent of the oil from the spill remained. That report estimated that burning, skimming and direct recovery from the wellhead removed 25 percent of the oil released from the wellhead.  Another 25 percent of the oil naturally evaporated or dissolved, and 24 percent was dispersed (either naturally or as a result of operations) as microscopic droplets into the ocean. That leaves just 26 percent, which the report says is either on or just below the surface as light sheen and weathered tar balls, has washed ashore or been collected from the shore, or is buried in sand and sediments.

Hopkinson says the reports arrive at different conclusions largely because the Sea Grant and UGA scientists estimate that the vast majority of the oil classified as dispersed, dissolved or residual is still present, whereas the NIC report has been interpreted to suggest that only the “residual” form of oil is still present.

The group has also estimated how much of the oil could have evaporated, degraded or weathered as of the date of the report. Using a range of evaporation and degradation estimates, the group calculates that 70-79 percent of oil spilled into the Gulf still remains. The group showed that it was impossible for all the dissolved oil to have evaporated because only oil at the surface of the ocean can evaporate into the atmosphere and large plumes of oil are trapped in deep water.

Another difference is that the NIC report estimates that 4.9 million barrels of oil were released from the wellhead, while the Sea Grant report uses a figure of 4.1 million barrels since .8 million barrels were piped directly from the well to surface ships and, therefore, never entered Gulf waters.

On a positive note, the group notes that natural processes continue to transform, dilute, degrade and evaporate the oil. They add that circular current known as the Franklin Eddy is preventing the Loop Current from bringing oil-contaminated water from the Gulf to the Atlantic, which bodes well for the East Coast.

Co-author Samantha Joye, professor of marine sciences at UGA, says that both the NIC report and the Sea Grant report are best estimates and she emphasises the need for a sustained and coordinated research effort to better understand the impacts of what has become the world’s worst maritime oil spill. She warns that neither report accounted for hydrocarbon gasses such as methane.

“That’s a gaping hole because hydrocarbon gasses are a huge portion of what was ejected from the well,” says Joye.

Co-authors on the paper include Jay Brandes, associate professor, Skidaway Institute of Oceanography; Samantha Joye, professor of marine sciences, UGA; Richard Lee, professor emeritus, Skidaway; and Ming-yi Sun, professor of marine sciences UGA.

To read the report in full, click here.

Image: Flickr -  f650biker