The underwater plumes spreading in the Gulf of Mexico have emerged as the most worrisome and scientifically provocative environmental story following the Deepwater Horizon spill. But researchers funded by the National Science Foundation (NSF) and affiliated with Woods Hole Oceanographic Institute (WHOI) recently reported that one of the most dire predictions may not be accurate.
From June 19 to 28, the scientific team used an autonomous underwater vehicle equipped with an underwater mass spectrometer to investigate a hydrocarbon plume at least 22 miles long, 1.2 miles wide, and 650 feet deep located 3,000 feet under the Gulf surface.
The plume was found to be moving at about 0.17 miles per hour southwest of the blowout.
Based on about 57,000 discrete chemical analyses, the researchers said the plume was characterized by a class of petroleum hydrocarbons at concentrations of more than 50 micrograms per liter. These samples had no odor of oil and were clear. This does not mean that the plume is not harmful to the environment, said one researcher.
Also, the results show that the plume is not being degraded by marine microbes as quickly as some anticipated. This means that the plume could travel considerable distances before degradation.
However, the investigation found no dead zones inside the plume. Dead zones are regions of significant oxygen depletion where almost no fish or other marine animals could survive.
Of the dozens of samples analyzed for oxygen, only a few from the plume layer had oxygen below expected levels, and even these samples were only slightly depleted, reported NSF and WHOI.
Information about the project is at http://www.whoi.edu/page.do?pid=7545&tid=282&cid=79926&ct=162.