Application of Resource-Ratio Theory to Hydrocarbon Biodegradation

Resource-ratio theory is one of the major logical frameworks used in ecology to predict how competition for growth-limiting resources influences biological diversity and function within a biological community. This paper presents experimental and other evidence that resourceratio theory can also be applied to nutrient supplementation in hydrocarbon biodegradation. The theory makes two major predictions about nutrient supply and hydrocarbon biodegradation: (i) that changes in nitrogen (N) and phosphorus (P) supply ratio conditions will significantly alter biodegradation rates and that these changes in N:P ratio will cause significant shifts in microbial community composition and (ii) that changes in absolute nutrient supply levels, at constant supply ratios, will alter total hydrocarbondegrader biomass, resulting in altered rates of hydrocarbon biodegradation. Here we analyze data from previous experiments studying the effects of N and P supply conditions on hexadecane and phenanthrene degradation in soil slurry reactors. Through the development of resource supply maps relating degradation rate and N and P supply conditions, it is shown that hydrocarbon degradation in slurry reactors is consistent with both major predictions of the theory. Further supporting evidence from previous studies on crude oil degradation in Arctic soils, hydrocarbon degradation in marine oil spills, and hydrocarbon composting in soils is also discussed in the context of resource-ratio theory. The paper suggests that more specific experimental studies are needed to verify further the utility of theory and that, once more extensive data are available, the theory should provide a strong theoretical foundation for optimizing nutrient formulation and application strategies for hydrocarbon degradation in the future.