Scientists funded by the National Science Foundation (NSF) and affiliated with the Woods Hole Oceanographic Institution (WHOI) have detected a plume of hydrocarbons—not pure oil, but with oil compounds—at least 22 miles long and more than 3,000 feet below the surface of the Gulf of Mexico, a residue of the BPDeepwater Horizon oil spill.
The 1.2-mile-wide, 650-foot-high plume of trapped hydrocarbons was detected during a ten-day subsurface sampling effort from 19-28 June 2010 near the wellhead. The results provide a snapshot of where the oil has gone as surface slicks shrink and disappear. A paper on the results was published in this week’s issue of the journal Science.
The researchers measured petroleum hydrocarbons in the plume and, using them as an investigative tool, determined that the source of the plume could not have been natural oil seeps but had to have come from the Deepwater Horizon blowout at the Macondo well.
They reported that deep-sea microbes were degrading the plume relatively slowly, and that it was possible that the plume had and could persist for some time if the rate of microbial degradation or the dilution of the plume does not accelerate.
These findings confirm what NOAA and our federal partners have reported about the presence and concentration of subsurface oil, and provide an additional piece of the puzzle as we continue to aggressively monitor the fate of the oil in the Gulf. Our collaborations with Woods Hole and other academic and private research institutions are critical to the ongoing response and recovery efforts.
—Steve Murawski, NOAA’s chief scientist
The research team based its findings on some 57,000 discrete chemical analyses measured in real time during a cruise aboard the R/V Endeavor, which is owned by NSF and operated by the University of Rhode Island.
The scientists used two advanced technologies: the autonomous underwater vehicle (AUV) Sentry and a type of underwater mass spectrometer known as TETHYS (Tethered Yearlong Spectrometer).
Whether the plume’s existence poses a significant threat to the Gulf is not yet clear, the researchers say.
We don’t know how toxic it is and we don’t know how it formed, or why. But knowing the size, shape, depth, and heading of this plume will be vital for answering many of these questions.
—Christopher Reddy, WHOI marine geochemist
The researchers detected a class of petroleum hydrocarbons at concentrations of more than 50 micrograms per liter. The water samples collected at these depths had no odor of oil and were clear.
- Richard Camilli, Christopher M. Reddy, Dana R. Yoerger, Benjamin A. S. Van Mooy, Michael V. Jakuba, James C. Kinsey, Cameron P. McIntyre, Sean P. Sylva, and James V. Maloney (2010) Tracking Hydrocarbon Plume Transport and Biodegradation at Deepwater Horizon. Science doi:10.1126/science.1195223