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Images: What Happened to Deepwater Horizon Oil?

Hopane, a component of oil, is a large, complex compound with many branches and rings. Microbes typically leave behind larger, more complex compounds that require more effort to break down. In a new study, scientists were surprised to find that in the frigid abyss on the seafloor of the Gulf of Mexico, microbes did decompose hopane. Hopane is generally so resistant to degradation that oil-spill scientists have come to rely on it as a reference against which to measure the relative degradation of all other compounds, and to help “fingerprint” the source of where oil came from. The new finding throws a curveball to oil-spill scientists, who can no longer assume that hopane and other complex hydrocarbons don’t break down in the environment. (Illustration by Eric S. Taylor, WHOI Graphic Services)
A new study on what happened to oil spilled during the Deepwater Horizon disaster suggests that microbes may be able to degrade small oil particles more rapidly than large ones, because small particles have more exposed surface area. The evidence suggests that the subsurface release of dispersants, which keep oil droplets from clumping together, may have boosted the activity of microbes and the breakdown of spilled oil. (Illustration by Eric S. Taylor, WHOI Graphic Services)
Oil and gas were trapped in a plume that flowed at depth from the damaged Macondo well in the Deepwater Horizon disaster in the Gulf of Mexico. In a 2014 study, scientists proposed that tiny droplets of oil in the plume coagulated and sank to the seafloor—much of it within 45 miles of the well. (Illustration by Jack Cook, WHOI Graphic Services)
A remotely operated deep-sea vehicle is loaded with plastic cylinders to be used as push-cores to take samples of seafloor sediments contaminated by the Deepwater Horizon oil spill in the Gulf of Mexico. (Photo by David Valentine, University of California, Santa Barbara)
Some 160 million gallons of oil gushed for 87 days into the Gulf of Mexico during the Deepwater Horizon disaster in 2010. Officials also discharged 1.67 million gallons of chemicals into the ocean to disperse the oil. (Photo by Dan Torres, Woods Hole Oceanographic Institution)
In the Deepwater Horizon disaster, oil from the damaged Macondo well on the seafloor rose and formed slicks at the surface that spread far and wide (lavender), driven by winds and currents in the Gulf of Mexico. But some portion of the oil was trapped on the bottom and never rose to the surface. Scientists studied samples of seafloor sediments (dots) and focused on a telltale chemical, hopane, to determine that the trapped oil settled in a relatively small area near the well (box). (Image courtesy of G. Burch Fisher, University of California, Santa Barbara)
Scientists found elevated levels of hopane from Deepwater Horizon oil within a 1,250-square-mile box near the damaged well (star) and near communities of deep-sea corals damaged by the oil spill (circles). They found that 4 to 31 percent of the oil trapped in the deep ocean—the equivalent of 2 to 16 percent of the total oil discharged during the accident—fell within that 1,250-square-mile patch. (Image courtesy of David L. Valentine, University of California, Santa Barbara)
This article's authors, marine chemists Chris Reddy (left) of the Woods Hole Oceanographic Institution and David Valentine of the University of California, Santa Barbara, flew above the Gulf of Mexico to observe the aftermath of the Deepwater Horizon oil spill. (Photo courtesy of Chris Reddy, Woods Hole Oceanographic Institution)
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