Bugs to the Rescue in the Gulf
September 1, 2010 § Leave a comment
This piece was energized by the August RTEC Breakfast Forum
At the RTEC Breakfast Forum, Offshore Drilling: a Risk Worth Taking?, special guest, Dr. Jennie Hunter-Cevera from RTI International, kicked off a stimulating discussion on the possible role of microbes in eradicating the Gulf of Mexico of oil spilled from Deepwater Horizon. She informed us that in the Exxon Valdez spill, bacteria had been imported due to insufficient naturally occurring species in those waters. This specific strain had a special “suicide gene” to ensure death after the job was done.
The Gulf of Mexico on the other hand is known to have a thriving population of these critters, in part due to natural seeps and continual small spills. These latter were described in a recent paper in Nature. (See our July 8, 2010 post of Interesting Reads)
Earlier in August, federal government scientists set off considerable debate when they opined that the majority of oil had been consumed in some fashion. Certainly, visible oil is not very much in evidence. Dueling scientists have been debating the fate of the oil and no doubt will continue to do so.
Shortly after the blowout, BP commenced the massive use of the dispersant, COREXIT, which manufacturer, Nalco, claims to be biodegradable. At that time they, and the EPA officials who permitted it, came in for a lot of criticism.
Critics, such as Dr. Terry Hazen of UC Berkeley, contended that the dispersants would do more harm than good. Dr. Hazen, a microbial ecologist who acted as an advisor to BP on behalf of the DOE reported this.
That was in June. In August, Dr. Hazen and coauthors published a paper in the journal, Science, which decidedly reversed course in that dispersants were now shown as beneficial. Here is a report on the findings.
Dispersants were intended to break the oil into smaller droplets. Critics believed that the smaller size would make them more amenable for fish to consume. BP has been silent on their reasons, but one can assume they believed that the bacterial action would be enhanced by the smaller drops. Nobody disputes these three premises concerning the bacteria: they do in fact consume oil, they multiply in the presence of food and die off when the food supply goes way. Critics felt that the dispersant laden oil would sink below the surface and not be available for bacterial action due to colder waters below with less oxygen.
Undoubtedly, the suspicion prevailed that getting rid of a visible sheen was a BP priority. Recent congressional testimony has scientists reporting that the dispersed oil was now in plumes that concentrated at depths around 3,000 feet. Concern arose for marine organisms at those depths. Out of sight, but not out of danger was the refrain.
Enter the aforementioned Dr. Hazen stage left. He led an expedition on May 25 to sample the plumes. They used a relatively new chip that conducts a rapid DNA based microarray without the need for culturing. Thus, bacteria could be identified precisely and quickly. What they found was a new species of psychrophilic (cold loving) bacteria that thrived at the 5 degrees Centigrade temperatures at those depths. These were close relatives of known oil consuming bacteria.
Further, scientists were concerned that even if bacteria existed, they would deplete available oxygen. This would then lead to “dead zones,” a phenomenon already known to exist as a body of water where life cannot be supported. Dr. Hazen and colleagues discovered that these wondrous new creatures did their job with minimum oxygen consumption. They measured the oxygen saturation to be 59% within the plume, compared to 67% outside it. All this falls neatly in the “Isn’t Nature Wonderful” category. Needless to say, Dr. Hazen is now a believer in the use of dispersants.
Dr. Hazen’s team observed that the oil is being consumed at a fast rate, due to the relatively light crude, with a high proportion of low molecular weight species. The only report I could find places the API gravity of the spill at 33 degrees, which is pretty light, considering how the API must exceed 34 to be classified light.
Also, the very heavy molecules generally will not be consumed by the bacteria and will be left with balls of “tar.” (This is why beaches close to natural seeps have tar balls.) Some of the beaches in Barbados have bottles of solvent placed by the adjacent hotels. Based on the reported character of the oil, the tar balls from the blowout should be minor in quantity, if the bacteria do their job.
A final footnote of interest: Dr. Hazen’s work was funded by the Energy Biosciences Institute at Berkeley (EBI). The EBI is comprised of The University of California-Berkeley and The University of Illinois. Coincidentally, they are funded by BP to the tune of $500 million over 10 years. At the time of the award, it was the largest grant of its kind, dwarfing a similar ExxonMobil award of about $200 million to Stanford.
In addition, the principal executive on the giving side was Steve Koonin, then Chief Scientist at BP. The principal recipient was Steve Chu. These two are respectively co-number two and number one at the DOE today. One does wonder whether Dr. Hazen was given a bit of a nudge by DOE high ups.
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