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dc.contributor.authorTuit, Caroline Beth  Concept link
dc.coverage.spatialSargasso Sea
dc.coverage.spatialArabian Sea
dc.coverage.spatialEastern Tropical Pacific
dc.coverage.spatialCaliforna
dc.date.accessioned2008-10-01T13:48:46Z
dc.date.available2008-10-01T13:48:46Z
dc.date.issued2003-02
dc.identifier.urihttps://hdl.handle.net/1912/2431
dc.descriptionSubmitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2003en
dc.description.abstractPrevailing wisdom holds that the vertical distribution of molybdenum (Mo) in the open ocean is conservative, despite Mo's important biological role and association with Mn oxides and anoxic sediments. Mo is used in both nitrogenase, the enzyme responsible for Nz fixation, and nitrate reductase, which catalyzes assimilatory and dissimilatory nitrate reduction. Laboratory culture work on two Nz fixing marine cyanobacteria, Trichodesmium and Crocosphaera, and a marine facultative denitrifier, Marinobacter hydrocarbanoclasticus, showed that Mo cell quotas in these organisms were positively correlated with Mo-containing enzyme activity. Mo concentrations in Crocosphaera dropped almost to blank levels when not fixing Nz suggesting daily synthesis and destruction of the entire nitrogenase enzyme and release of Mo. Trichodesmium cultues, however, retained a pool of cellular Mo even when not fixing Nz. Colonies of Trichodesmium collected in the field have Mo:C tenfold higher than seen in culture, these Mo:C ratios were reflected in SPM samples from the same region. Fe:C ratios for Trichodesmium were between 12-160 μmol:mol in field and cultured samples. The Fe:C ratio of Crocosphaera was established to be 15.8±11:3 under Nz fixing conditions. Mo cellular concentrations in cultured organisms were too small to significantly influence dissolved Mo distributions, but may slightly affect Suspended Particulate Matter (SPM) distributions. Mean SPM Mo:C ratios were slightly elevated in regions of Nz fixation and denitrification. A high precision (±0.5%) isotope dilution ICP-MS method for measuring Mo was developed to re-evaluate the marine distribution of Mo in the dissolved and particulate phase. Mn oxides were not found to significantly influence either the dissolved or SPM Mo distribution. Dissolved Mo profiles from the Sargasso and Arabian Sea were conservative. However, dissolved Mo profiles from the Eastern Tropical Pacific showed both depletion and enrichment of dissolved Mo possibly associated with interaction of Mo with coastal sediments. Dissolved Mo profiles in several California Borderland Basins showed 1-2 nM Mo depletions below sill depth. A more focused study of water column response to sediment fluxes using the high precision Mo analyses is necessary to determine whether these phenomena are related.en
dc.description.sponsorshipThis work was funded by a grant from the National Science Foundation (#OCE-0096453) and the WHOI Academic Programs Ocean Ventures Fund. I have also been supported through WHOI by a NSF coastal traineeship #DGE-9454129, by the US GS Cooperative Agreement #USGS-OOHQAG001 and by WHOI Academic Programs.en
dc.format.mimetypeapplication/pdf
dc.language.isoen_USen
dc.publisherMassachusetts Institute of Technology and Woods Hole Oceanographic Institutionen
dc.relation.ispartofseriesWHOI Thesesen
dc.subjectSeawateren_US
dc.subjectMarine sedimentsen_US
dc.subjectMolybdenumen_US
dc.subjectNitrogenen_US
dc.subjectAtlantis (Ship : 1996-) Cruise AT3-11en_US
dc.subjectAtlantis (Ship : 1996-) Cruise AT7-5en_US
dc.subjectSeward Johnson (Ship) Cruiseen_US
dc.titleThe marine biogeochemistry of molybdenumen
dc.typeThesisen
dc.identifier.doi10.1575/1912/2431


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