9521983 Joye Nitrification, a central process in the nitrogen cycle, may significantly alter partitioning of the regenerated nitrogen flux between release from sediments to the water column as ammonium versus loss as dinitrogen gas via coupled denitrification. Nitrogen release from freshwater sediments consists of comparable amounts of dinitrogen gas and ionic forms, suggesting that coupled nitrification-denitrification is more efficient in freshwater than in marine environments. This team of investigators will examine the effects of methane and hydrogen sulfide, which differ in concentration and distribution between marine and freshwater environments, on nitrification. They hypothesize that co-metabolism affects the spatial and temporal distribution of nitrification in aquatic sediments, particularly in freshwater environments. They will examine the role of competitive (substrate) interactions and the effect of variations in the oxidizing bacterial community composition (presence of nitrifying vs. methane-oxidizing bacteria) on nitrification. They also hypothesize that hydrogen sulfide, a potent inhibitor of nitrification, may affect the spatial and temporal distribution of nitrification in marine sediments. Understanding the relationship between bacterial community composition, bacterial physiology and geochemically-driven changes in physiology will improve our understanding of nitrogen cycling in sediments and will provide a conceptual framework for improved predictive models of coupled nitrification-denitrification.
