FIELD EVALUATIONS OF MARINE OIL-SPILL BIOREMEDIATION

Bioremediation is defined as the act of adding or improving the availa bility of materials (e.g., nutrients, microorganisms, or oxygen) to co ntaminated environments to cause an acceleration of natural biodegrada tive processes. The results of field experiments and trials following actual spill incidents have been reviewed to evaluate the feasibility of this approach as a treatment for oil contamination in the marin env ironment. The ubiquity of oil-degrading microorganisms in the marine e nvironment is well established, and research has demonstrated the capa bility of the indigenous microflora to degrade many components of petr oleum shortly after exposure Studies have identified numerous factors which affect the natural biodegradation rates of oil such as the origi n and concentration of oil, the availability of oil-degrading micro-or ganisms, nutrient concentrations, oxygen levels; climatic conditions, and sediment characteristics. Bioremediation strategies based on the a pplication of fertilizers have been shown to stimulate the biodegradat ion rates of oil in aerobic intertidal sediments such as sand and cobb le. The ratio of oil loading to nitrogen concentration within the inte rstitial water has been identified to be the principal controlling fac tor influencing the success of this bioremediation strategy. However t he need for the seeding of natural environments with hydrocarbon-degra ding bacteria has not been clearly demonstrated stated under natural e nvironmental conditions. It is suggested that bioremediation should no w lake its place among the many techniques available for the treatment of oil spills, although there eis still a clear need to set operation al limits for its use. On the basis of the available evidence, we have proposed preliminary operational guidelines for bioremediation or on shoreline environments.