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Influences on the oceanic biogeochemical cycling of the hybrid-type metals : cobalt, iron, and manganese

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dc.contributor.author Noble, Abigail E.
dc.coverage.spatial Hawaii
dc.coverage.spatial South Atlantic
dc.coverage.spatial McMurdo Sound
dc.date.accessioned 2012-02-09T21:52:47Z
dc.date.available 2012-02-09T21:52:47Z
dc.date.issued 2012-02
dc.identifier.uri http://hdl.handle.net/1912/5027
dc.description Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, February 2012 en_US
dc.description.abstract Trace metal cycling is one of many processes that influence ocean ecosystem dynamics. Cobalt, iron, and manganese are redox active trace metal micronutrients with oceanic distributions that are influenced by both biological and abiotic sources and sinks. Their open ocean concentrations range from picomolar to nanomolar, and their bioavailabilities can impact primary production. Understanding the biogeochemical cycling of these hybrid-type metals with an emphasis on cobalt was the focus of this thesis. This was accomplished by determining the dissolved distributions of these metals in oceanic regions that were characterized by different dominant biogeochemistries. A large subsurface plume of dissolved cobalt, iron, and manganese was found in the Eastern South Atlantic. The cause of this plume is a combination of reductive dissolution in coastal sediments, wind-driven upwelling, advection, biological uptake, and remineralization. Additional processes that are discussed as sources of metals to the regions studied during this thesis include isopycnal uplift within cold-core eddies (Hawaii), ice melt (McMurdo Sound, Antarctica), riverine input (Arctic Ocean), and winter mixing (McMurdo Sound). The biological influence on surface ocean distributions of cobalt was apparent by the observation of linear relationships between cobalt and phosphate in mid to low latitudes. The cobalt:phosphate ratios derived from these correlations changed over orders of magnitude, revealing dynamic variability in the utilization, demand, and sources of this micronutrient. Speciation studies suggest that there may be two classes of cobalt binding ligands, and that organic complexation plays an important role in preventing scavenging of cobalt in the ocean. These datasets provided a basis for comparing the biogeochemical cycles of cobalt, iron, and manganese in three oceanic regimes (Hawaii, South Atlantic, McMurdo Sound). The relative rates of scavenging for these metals show environmental variability: in the South Atlantic, cobalt, iron, and manganese were scavenged at very different rates, but in the Ross Sea, mixing and circulation over the shallow sea was fast, scavenging played a minor role, and the cycles of all three metals were coupled. Studying the distributions of these metals in biogeochemically distinct regions is a step toward a better understanding of their oceanic cycles. en_US
dc.description.sponsorship Funding for this research was provided by the the National Science Foundation Chemical Oceanography (Division of Ocean Sciences OCE-0452883, OCE-0752291, OCE-0928414, OCE-0732665, OCE-0440840, OCE-0327225), the Center for Microbial Research and Education, the WHOI Coastal Ocean Institute, and the WHOI Ocean Life Institute, WHOI Academic Programs Office, and a Fye Teaching Fellowship. en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher Massachusetts Institute of Technology and Woods Hole Oceanographic Institution en_US
dc.relation.ispartofseries WHOI Theses en_US
dc.subject Nutrient cycles en_US
dc.subject Ocean circulation en_US
dc.title Influences on the oceanic biogeochemical cycling of the hybrid-type metals : cobalt, iron, and manganese en_US
dc.type Thesis en_US
dc.identifier.doi 10.1575/1912/5027


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