Collaborative Research: Seawater Inorganic and Organic Carbon Measurements for the US GEOTRACES Eastern Pacific Zonal Transect

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Scientists from Bermuda Institute of Ocean Sciences and the University of California, Santa Barbara, plan to collect samples during the 2013 GEOTRACES Eastern Pacific Zonal Transect cruise and analyze them for dissolved inorganic carbon, dissolved organic carbon (DOC), and total alkalinity. The resultant data will be highly precise and accurate to allow calculation of pH and seawater carbonate chemistry (e.g., hydroxide, carbonate ion, saturation sate for calcium carbonate minerals). Given the influence of pH on redox chemistry, speciation, and ligand-particle-trace metal/isotope interactions, the transect from Peru to Tahiti with its range of marine seawater carbonate chemistry will provide an opportunity to test the hypotheses that (1) pH is a critical constraint for controlling distributions of trace elements and their isotopes (TEIs) and their dynamics within the water column, and; (2) DOC interacts with TEIs providing a spectrum of binding ligands that influence trace element solubility, complexation, and speciation. Also, because the cruise track will pass over the East Pacific Rise, the scientists plan to evaluate DOC variability within the hydrothermal plume and determine the partitioning of organic matter between DOC and particulate organic carbon. In collaboration with other GEOTRACES researchers, the data will be used to assess the speciation of iron, copper, cobalt and mercury, as well as determine the removal rate of DOC from the surface ocean with the help of chlorofluorocarbon data obtained by a collaborator from the University of Miami, Rosenstiel School of Marine and Atmospheric Science. As regards broader impacts, this project would result in a high quality data set that would benefit not only the GEOTRACES community to help them interpret their trace metal and isotope measurements but other scientists involved in organic/inorganic carbon cycle research as well. One graduate student from the University of California, Santa Barbara would be supported and trained as part of this project.