Both dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) will be measured by the new high-temperature catalytic oxidation technique as part of the U.S. JGOFS Equatorial Pacific Program. Survey measurements will provide critically needed data for constraining upper ocean models of the carbon flux and to determine if DOC and DON concentrations vary seasonally in the upper ocean at the equator. On board incubation studies will (1) attempt to observe net production of dissolved organic matter by natural populations, (2) measure bacterial oxidation rates and (3) by combining DOC and DON measurements, determine the C/N ratio of the biologically labile material. The C/N ratio of the dissolved material will provide critically needed information regarding the nature of the biologically labile fraction of the dissolved organic carbon pool. Post-cruise incubation studies will look at long-term stability of DOC and DON and whether the C/N ratio changes as bacteria remineralize organic matter. Additional experiments will address problems of saving DOC and DON samples for future analysis and whether changes occur during storage. These studies will be conducted in collaboration with other U.S. JGOFS investigators.
