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dc.contributor.advisorBianchi, Thomas S.en_US
dc.creatorShen, Lien_US
dc.date.accessioned2012-02-14T22:20:37Zen_US
dc.date.accessioned2012-02-16T16:19:32Z
dc.date.available2014-01-15T07:05:31Z
dc.date.created2011-12en_US
dc.date.issued2012-02-14en_US
dc.date.submittedDecember 2011en_US
dc.identifier.urihttp://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10614en_US
dc.description.abstractAlthough there has been considerable work on the role of nutrient-derived (mostly nitrate) primary production in fueling hypoxia in northern Gulf of Mexico, very little is known about the relative importance of autochthonous versus allochthonous sources of dissolved organic matter (DOM). Moreover, even less is known about the importance of dissolved organic nitrogen (DON), a critical component of DOM (along with DOC) in supporting hypoxia in this region. Most nitrogen in marine organisms exists in the form of amino acids. Changes in the spatial and temporal distribution of amino acids in the Mississippi River Plume have been shown to be important in the dynamic microbial cycling in the plume. In this study, concentrations of amino acids, DON and DOC were linked with hydrography data (e.g., DO, salinity, temperature, fluorescence) to determine how these sources of DOM are related to seasonal and diurnal changes in hypoxia on the inner Louisiana shelf. The general working hypothesis of this work was that allochthonous and autochthonous sources of DOM on the Louisiana shelf have been largely underestimated in their role in fueling hypoxia in northern Gulf of Mexico. A positive correlation between DOC, DON and fluorescence demonstrated that the main source of both DOC and DON was likely to be in situ phytoplankton production. Surface waters in the near-field showed this relationship more than at stations to the west where a sub-surface chlorophyll peak near the pycnocline may also provide a source of DOC and DON in bottom waters. DFAA always had relatively low concentrations at all water depths, which further supports prior work which has shown rapid cycling and high consumption rate of DFAA by heterotrophic bacteria. In addition to biotic controls, selective adsorption of DFAA likely contributed to the dominance of aspartic and glutamic acids at our stations. Hypoxia was generally observed in bottom waters in both spring and summer 2010. Dissolved oxygen generally revealed a negative correlation with nitrate+nitrite concentrations. Based on other work, one possible reason for such linkages may be from NH4+ released from dissimilatory nitrate reduction to ammonium (DNRA). Another possible reason may be the high degradation of labile DOM (such as DFAA) as shown by high respiration in bottom waters in prior work by Amon and Benner (1998).en_US
dc.format.mimetypeapplication/pdfen_US
dc.language.isoen_USen_US
dc.subjectGulf of Mexicoen_US
dc.subjecthypoxiaen_US
dc.subjectDOMen_US
dc.subjectDOCen_US
dc.subjectDFAAen_US
dc.titleDissolved Organic Matter Cycling on the Louisiana Shelf: Implications for the Formation of Hypoxiaen_US
dc.typeThesisen
thesis.degree.departmentOceanographyen_US
thesis.degree.disciplineOceanographyen_US
thesis.degree.grantorTexas A&M Universityen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.levelMastersen_US
dc.contributor.committeeMemberChapman, Piersen_US
dc.contributor.committeeMemberThornton, Danielen_US
dc.contributor.committeeMemberAmon, Raineren_US
dc.type.genrethesisen_US
dc.type.materialtexten_US
local.embargo.terms2014-01-15en_US


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