Sunday, March 16, 2014

Micro-Organismal Degradation of Oil Spills

BP Deepwater Horizon Oil Spill- Google Map Image (www.eoearth.org)
Oil spills like the Exxon-Valdez and BP Deepwater Horizon incidents are devastating to aquatic and terrestrial wildlife.  Much research has been done surrounding the most effective way of cleaning up oil slicks and/or plumes in the water and the shoreline.  With petroleum hydrocarbons occurring naturally in the environment, microorganisms are professionals at degrading these compounds.  Hundreds of species of bacteria and fungi are capable of breaking down petroleum hydrocarbons with the help of dispersants and fertilizers.  Although weathering processes and degradation by microorganisms are very effective, patches of highly weathered oil likely will remain in some environments.  In remediation, decisions to rely upon microbial oil biodegradation should be driven by risk to the environment and not just the presence of detectable hydrocarbons.    

In the first study I will reference in my talk, the researchers found that temperature had a greater effect than nutrient addition when degrading petroleum hydrocarbons.  They support the finding that there is an immediate change in bacterial community structure when crude oil is released into the water column.  They also noted that certain species that are “hydrocarbonoclastic” function at a range of 4-20°C, so organisms can be used to bioremediate the area seasonally.

The second study I found had a related author from the first paper, and this study quantified changes in concentrations of hydrocarbonoclastic bacteria in response to intervention strategies applied to external organisms.  Intervention strategies included adding nutrients, bioemulsifers, and bioaugmentation with other types of bacteria.  Overall, nutrient and bioemulsifier addition proved to be a synergistic mixture.  Alcanivorax enhanced degradation significantly over Thalassolituus, but the use of the synergistic mixture and the bacteria would improve mitigation strategies.

The third paper specifically relates the growth in population of λ-Proteobacteria to the Deepwater Horizon oil spill in the Gulf of Mexico.  With the spill being completely underwater as a plume rising to the surface, deep sea λ-Proteobacteria who degrade petroleum, increased due to the spill.  Changes in hydrocarbon composition with distance from the source and incubation experiments with environmental isolates demonstrated faster than expected hydrocarbon biodegradation rates at 5°C.  Based on these results, intrinsic bioremediation of the oil plume in the deep-water column without substantial oxygen drawdown is possible.

I am still researching some more primary literature to add to my talk.  This may include some supplementary information on other clean-up methods used besides bioremediation and more information about the biological implications of oil spills.

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