9633510 CAPONE N2 Fixation as a Source of New N in the Oligotrophic Tropical Oceans This project will examine the importance of the nitrogen-fixing cyanobacteria, Trichodesmium, in providing nitrogen to support biological production in tropical oceans. Nitrogen (N2) fixing bacteria are intensively studied worldwide, particularly in agricultural systems, reflecting their importance as sources of fertilizer nitrogen. Trichodesmium, the best known marine nitrogen fixer, is widely distributed throughout the tropical oceans, can form massive blooms, and possesses a number of unique metabolic adaptations for fixing nitrogen. Global nitrogen fixation by Trichodesmium may rival that in agricultural systems. Recent evidence indicates that the rate of nitrogen fixation by Trichodesmium has been severely underestimated, and this may account for the severe imbalances in the nitrogen budgets of several tropical oceanic biomes. This research will provide fundamental information on the physiology of Trichodesmium, will quantify its importance in the global carbon and nitrogen cycles, and will yield information to more accurately assess the biological capacity of tropical oceans to take up atmospheric carbon dioxide.
