Composition of 2010 Gulf Oil Plume Established

A major collaboration of scientists says that it finally managed to establish the chemicals that made up the vast plumes of oils that were spilled in the Gulf of Mexico during the devastating 2010 Deepwater Horizon oil spill. The data will help experts understand event's effects in more detail.

Investigators led by experts at the Woods Hole Oceanographic Institution (WHOI) collected data on the massive plumes, using robotic devices to collect water samples from a variety of locations in the affected areas.

While working in the Gulf of Mexico last summer, the team discovered a 22-mile, hydrocarbon-containing oil plume, which they analyzed in great detail. They even mapped the extent of the debris, since this could also provide key indicators of its characteristics.

Interestingly, the composition of the plume was not as the team expected. Some chemicals appeared to have made their way inside quite easily, whereas others were not represented at all. Experts were very curious to learn why this difference existed.

Details of their work appear in this week's online issue of the esteemed journal Proceedings of the National Academy of Sciences (PNAS). The study was funded by the US National Science Foundation.

The project was awarded three NSF Rapid Response Research grants, which enables scientists to go out into the field at a moment;s notice. “By any measure, this is a remarkable study,” explains the director of the NSF chemical oceanography program, Don Rice.

“Reddy and colleagues add several critical tiles to the growing Deepwater Horizon mosaic. We now have hints of why some earlier studies appear to refute one another,” he goes on to say.

“Most importantly, we now have a far better understanding of how and why an oil 'spill' into the ocean from below differs from one from above. The significance of this work extends well beyond the Gulf of Mexico,” the official adds.

WHOI chemist Christopher Reddy was the lead author of the study. The work revealed that the oil component of the plume included benzene, toluene, ethybenzene, and total xylenes (BTEX), at a concentration level of roughly 70 micrograms per liter.

These levels are “significantly higher than background. We don't know with certainty the adverse effects it might cause on marine life,” Reddy explains. Scientists say that lethal BTEX concentrations range between 5 to 50 milligrams per liter.

However, sublethal effects do occur. These may include for example neurological impairment in complex species, which may lose their ability to hunt or elude predators as a result. In other words, the animals would not be killed directly, but rather indirectly.