Measurements of isotopic ratios of nitrogen and oxygen will be made to evaluate the global significance of denitrification. Recent studies suggest the prevailing view that most marine nitrous oxide arises from nitrification may be in error. It is expected that Monterey Canyon and adjacent waters will provide a representative site for testing this hypothesis. Nitrous oxide is formed as an important intermediate in the marine nitrogen cycle, and all parts of the ocean contribute to the "greenhouse effect" by the evolution of this gas. Laboratory examination of the ratios of N-15/N-14 and 0-18/0-16 also will shed light on the question of whether or not globally significant denitrification can occur in water with oxygen concentrations greater than 2.5 micromolar.
