Opportunities for Environmental Applications of Marine Biotechnology Proceedings of the October 5-6, 1999, Workshop (2000) / Chapter Skim
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In Situ Bioremediation of Oiled Shoreline Environments
In Situ Bioremediation of Oiled Shoreline Environments
Pages 44-60
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From page 44... ...
, this technology is now considered one of the most promising oil spill countermeasures (Hoff 1993; Swannell and Head 1994~. BIOREMEDIATION STRATEGIES There are two main approaches to oil spill bioremediation: 1)
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From page 45... ...
Successful enhancement of oil degradation with allochthonous microbial cultures has been achieved only when chemostats or fermentors were used to control conditions and reduce competition from indigenous microflora (Won" and Goldsmith 1988~. Although commercial seed cultures may be useful in the treatment of specific compounds within crude oil that are relatively resistant to degradation and isolated spills in confined areas (Lee and Levy 1989a)
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From page 46... ...
The feasibility of adding inorganic nutrients on a periodic basis has been demonstrated in field trials as a means of sustaining elevated nutrient concentrations within the sediments for effective bioremediation (Lee and Levy 1989b, 1991; Venosa and others 1996~. The advantages of inorganic agricultural fertilizers as bioremediation agents include low cost, availability, and ease of application.
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Consideration is now being given to the inherent capacity of wetland plant species to aerate the rhizosphere as a means to stimulate aerobic oil biodegradation. Plants also may take up oil and release exudates and enzymes that stimulate microbial activity.
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Research during "Spills-of-Opportunity" In terms of a spill incident case study, the most rigorous study of bioremediation was conducted by Exxon and the US Environmental Protection Agency after the 1989 Exxon Valdez spill in Alaska. Preliminary laboratory experiments demonstrated the potential of nutrient enrichment as a bioremediation treatment (Pritchard and Costa 1991; Pritchard and others 1992~.
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Monitoring hydrocarbon losses relative to this conserved biomarker provided benchmark confirmation of oil biodegradation. Fertilizer additions were reported to accelerate the rate of oil removal by a factor of two to five.
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Toxicity and Other Environmental Impacts The public has responded favorably to bioremediation strategies based on nutrient enrichment because the implicit goal is that of reducing toxic effects by converting organic molecules to benign cell biomass and "environmentally friendly" products like carbon dioxide and water (Atlas and Cerniglia 1995~. Some environmentalists have expressed concern about the net benefit of bioremediation strategies because of the potential production of toxic metabolic by-products, possible toxic components in the formulation of bioremediation agents, and the ineffective degradation of the most toxic components of residual oils (Hoff 1991; OTA 1991~.
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From page 51... ...
Study results clearly demonstrated that the success of bioremediation depends on the nature of the contaminated shoreline. On a sandy beach contaminated with low concentrations of Terra Nova crude oil, toxicity to the oil-degrading bacteria was not a factor, and ambient concentrations of nitrogen and phosphorus were sufficient to result in rapid oil biodegradation.
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From page 52... ...
Lower temperatures are thought to reduce the permeability of the coating on the slow-release fertilizer, effectively suppressing nutrient release rates. For optimal effectiveness, the selection of bioremediation agents should take into account the environmental conditions, the type of contaminated shoreline, and the methods of application (Lee and others 1993; Prince 1993; Swannell and others 1995, 1996~.
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From page 53... ...
In light of these results, it is suggested that interstitial nutrient levels be determined before any decision is made to apply bioremediation agents. Monitoring Remediation Effectiveness and Identification of Operational Endpoints Wide acceptance and use of bioremediation strategies by the oil spill response community has been limited by the lack of defined performance standards.
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From page 54... ...
As discussed, future operational guidelines will incorporate reliable microbial response and ecotoxicological monitoring protocols to verify efficacy for toxicity reduction over that of no treatment. In addition to direct chemical evidence of oil degradation, microscale biotests may provide an operational endpoint indicator for bioremediation on the basis of toxicity reduction; i.e., the site is acceptable as there is no detectable toxic effects, or the treatment is detrimental in that a toxic response is induced (Lee and others 1995b; Mearns and others 1995~.
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1993 Enhancement of spilled oil biodegradation by nutrients of natural origin. In: Proceedings of the International Oil Spill Conference.
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Swannell RPJ, Grant AL, Lee K 1995 Effect of Bioremediation agents on oil biodegradation in medium-fine sand.
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1999 Evaluating the addition of fine particles to enhance oil degradation. In: Proceedings of the International Oil Spill Conference.
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In: Proceedings of the 18th Arctic and Marine Oil Spill Program (AMOP) Technical Seminar, Environment Canada, p 1133-1145.
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From page 59... ...
Sugai SF, Lindstrom JE, Braddock JF. 1997 Environmental influences on the microbial degradation of Exxon Valdez oil on the shorelines of Prince William Sound, Alaska.
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From page 60... ...
Wrenn BA, Haines JR, Venosa AD, Kadhodayan M, Suidan MT. 1994 Effects of nitrogen source on crude oil biodegradation.
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