Only 25% of studies noted dispersants had a positive effect on growth of oil-eating microbes, 60% said it “retarded growth” — Positives are suspect

In it's Sunday edition, the Los Angeles Times attempts to unravel the "mystery" of oil dispersants.

The Times is reporting, "Mervin Fingas, a retired scientist with the Canadian government, said that of roughly 40 biodegradability studies he surveyed between 1997 and 2008, about 60% said dispersant retarded growth of oil-eating microbes and 15% reported no effect. The remaining 25% noted a positive effect."

And according to the Times, these "positive findings are open to interpretation."

Positive Finding? #1

  • "At a 1999 oil spill conference, researchers reported that microbial populations dining on oil treated with the dispersant Corexit 9500 (used by BP in the gulf) grew more than seven times as large as those eating oil dispersed physically, suggesting the bacteria were helping. Yet a comprehensive 2005 review of dispersants by the National Research Council concluded that the healthy bacterial growth in such studies could easily be due to microbes feeding on dispersant, not oil."

Positive Finding? #2

  • "A 2001 study by researchers at ExxonMobil Biomedical Sciences found that oil dispersed with Corexit 9527, also used on the BP spill, was twice as toxic to the inland silverside, an estuarine fish — but not if that crude had been exposed to the elements."

Unfortunately, "BP decided to spray much of the dispersant not onto the water surface, as is more common, but over oil pouring out of the leaking wellhead 5,000 feet under the sea," as the Times noted. This largely prevents crude from being "exposed to the elements" it normally would be on the surface by means of higher temperature, sunlight, air circulation, oxygen content, and wave action.

1 comment to Only 25% of studies noted dispersants had a positive effect on growth of oil-eating microbes, 60% said it “retarded growth” — Positives are suspect

  • Gary C

    Psychrophiles (microbes)(the bacteria mentioned by the professor in the article you reference) operate in temperatures from about freezing to about 68F. If the water is maintaining temps in this range, (cold), these critters can do good work. If the water is warmer than 68F, they are not
    doing any good remediation work.

    Sooooooo, whatever oil may be down in the cold, cold part of the Gulf of Mexico, the psychrophiles will be trying to digest it. Soon after they eat whatever they eat, they will be eaten by fishes that like living in the cold part of the Gulf. The consumers of the psychrophiles will be somewhat contaminated by the hydrocarbons in the critters. It takes awhile for them to fully digest the hydrocarbon and poop it out as something not quite so bad as what it was. Much of the oil particles are floating in water that is probably not as cold as 68F. The "dispersed oil" is buoyant, and hangs near the surface.

    (Psychrophiles are in a group of microbes that includes various sub-groups, and like thermophiles they are referred to as extremophiles because they operate in and enjoy "extreme conditions.") In composting, we work with huge populations of thermophiles. They like the heat. (Here on the coast, "Heat is us!")

    I help increase the alcanivorax borkumensis populations. These critters are within the correct focus for remediation work we consider for coastal remediation and restoration. And, there is a rather long list to add based upon microbes digesting abilities, what they like, and how long they are willing to operate...(given the nutrient values we provide for them in exchange for their energy delivering exudates). Even with the good work of the alcanivorax borkumensis, there will be continuing kills of little fishes that are eagerly eating these helpful critters that have cleaned up much of the "hanging oil." It is really a bad cycle at this point.

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