A decades-long debate over the dominant way that nitrogen is removed from the ocean may now be settled. Researchers found that both of the nitrogen 'exit strategies,' denitrification and anammox, are at work in the oceans. The debate centers on how nitrogen -- one of the most important food sources for ocean life and a controller of atmospheric carbon dioxide -- becomes converted to a form that can exit the ocean and return to the atmosphere where it is reused in the global nitrogen cycle....