Dr. McCarthy in collaboration with Dr. Garside of Bigelow Lab. will study nitrogen cycling and particulate matter and nitrate isotopic signature in the northern Sargasso Sea. The researchers will use the chemoluminescent nitrate technique and improved ammonium analysis to provide the most sensitive analysis to date of nitrogen cycling in oligotrophic waters. Nitrogen is a plant nutrient that is thought to limit biological productivity in much of the world ocean. The question of nitrogen cycling in oligotrophic oceans will be advanced by the application of the state of the art techniques applied in this work.