Investigation of Marine Organic Carbon Cycles in the North Pacific and Atlantic Oceans

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This project will complete ongoing investigations of the role of dissolved organic carbon (DOC) in oceanic carbon cycles. Speci- fically, radiocarbon (14C) and stable carbon isotope (13C) ratios will be measured in two DOC pools: the fraction oxidized by ultraviolet (uv) radiation, and the fraction oxidized by high- temperature (HT) combustion. These isotopic signatures, coupled with total DOC concentrations (uv and HT) and the 14C, 13C and 15N signatures of sinking and suspended particulate organic carbon pools, will further our understanding of the sources and rates of cycling of dissolved organic matter in the oceans. Isotopic signatures (14C, 13C) and total concentrations will be completed for DOC in seawater samples collected in the north central Pacific gyre, the Sargasso Sea, and the Santa Monica Basin off Southern California. Additional measurements will be made on samples to be collected in the Amazon River plume and from an open-ocean station in the northeast Pacific off Point Conception, California. These latter measurements will be in conjunction with E. Druffel, WHOI, and J. Bauer, Florida State University. It is also planned to confirm the DOC-HT 14C measurements by other oxidation techniques, such as ultrasonication and Hg(II) complexation of chloride ion coupled with uv irradiation. The goals of this project are directly related to those of the U.S. Joint Global Ocean Flux Study (GOFS).