Oil spills

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Introduction

Electron micrograph of the Ebola Zaire virus. This was the first photo ever taken of the virus, on 10/13/1976. By Dr. F.A. Murphy, now at U.C. Davis, then at the CDC.

As the demand for crude oil as energy source is fast increasing, accidental and associated oil spills have been more and more frequent during the process of exploration, production, transportation and storage. On land, oil spills are usually localized and the impact is limited in a certain area. However, when oil spills happened in marine it may result in very serious ecological risks and long-term environmental disturbance (Patin 2004, 737-748). The primary source of oil input into seas is usually associated with transportation by tankers and pipelines.

Once the oil spill happened, the oil will experience a series of physical, chemical and biological change, the effect of which is overall defined as “weathering”. However, this process happened in a limited speed in the natural environment and need long time for the contaminated environment to recover. Various remediation methods have been proposed, among which the biological remediation has drawn increasing attention recently. There are two general approaches: to apply fertilizers or surfactants in order to promote the microbial degradation process, and to add naturally occurring adapted microbial hydrocarbon degraders seeding (Mulkinsphillips and Stewart 1974, 915-922). The rate of biodegradation in a remediation site is highly dependent on the characteristics of spilled oil, the localized physical chemical environment, as well as the indigenous microbe’s communities. In order to better use bioremediation, lots of research are being conducted, focusing on both the biotic and abiotic factors influencing the degradation rate.

Physical environment

Oil spill can happen everywhere, from arctic to tropical marine, from soil to water, and therefore the physical and chemical environment of oil spill can vary significantly from one to other. Many factors have been proved to influence microbial degradation of petroleum, including physical status of oil spill, temperature, oxygen, nutrients, soil type and characteristics, and vegetation etc.

Physical status of oil spill

Physical status of oil spill is the most important factor determines the environment the petroleum degraders live. The status of oil spill and those environmental factors will have complex interactions and exert mark influence on microbial communities. Generally, there are two kinds of oil spills: Oil spill in water and oil spill in soil. The biggest different between them is the degree of spread. In soil, hydrocarbon is absorbed by plant and soil particles, limiting its spreading. Oil on soil surface will receive relatively ample oxygen which is crucial for biodegradation. Some portion will go deeper into the soil, but still within limited depth. In that situation, when oxygen becomes limiting factor, aeration is needed in order to enhance the bioremediation (PRINCE 1993, 217-242).

In marine environment, there can be a lot of forms oil; each has its own typical environment. Most of the oil normally spreads, forming a thin slick on the top of water body. A large portion of the oil also forms emulsions or dissolve the water. Some heavy portion will settle into to the bottom. The oxygen can be relatively easily obtained in the slick oil spill, but the nutrient sometimes is limited; the dissolved oil or oil emulsion droplets usually have chance to obtain both oxygen and nutrient when they travel through water column; the environment in the sediments is low in oxygen although the nutrient may not be limited. The difference in these environmental factors can create big different in the petroleum degradation process, for example, it was found that the petroleum hydrocarbons would persist for longer periods in reduced sediments than would it do in aerated surface oil layers (Hamnrick, Delaune, and Patrick 1980, 365-369). In addition, the toxic concentration, which is mostly caused by aromatic hydrocarbons, in different biota will also vary within several orders of magnitude. The toxicity has been proven to be crucial factor for biodegradation of petroleum hydrocarbon.

Microbial communities

What kind of microbes do we typically find in this environment? Or associated with important processes in this environment? Describe key groups of microbes that we find in this environment, and any special adaptations they may have evolved to survive in this environment. List examples of specific microbes that represent key groups or are associated with important processes found in this environment. Link to other MicrobeWiki pages where possible.

Are there important biological interactions that are important in this environment? Do these interactions influence microbial populations and their activities? How do these interactions influence other organisms? Describe biological interactions that might take place in this environment, using as many sections/subsections as you require. Look at other topics available in MicrobeWiki. Create links where relevant.

Microbial processes

What microbial processes define this environment? Describe microbial processes that are important in this habitat, adding sections/subsections as needed. Look at other topics in MicrobeWiki. Are some of these processes already described? Create links where relevant.

Current Research

Enter summaries of recent research here--at least three required

References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by <your name>, a student of Angela Kent at the University of Illinois at Urbana-Champaign.