Macronutrient and carbon dioxide system interactions

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Chemical Oceanography

First Committee Member

Frank J. Millero, Committee Chair


This thesis investigates the interactions of biogeochemical cycles through the direct measurement of carbon dioxide and macronutrient system parameters in various marine ecosystems. To enable this study, existing carbon dioxide system and macronutrient techniques were improved and modified. Innovative aspects of this work include the use of liquid core waveguides for the colorimetric measurement of macronutrients and an improved system for the analysis of total inorganic carbon dioxide, building upon a preexisting non-dispersive infrared technique. Validation experiments indicate the automated high time-resolution TCO2 analyzer is capable of discrete analysis at a rate of one sample approximately every seven minutes with a precision of 0.1--0.2%. Investigations of CO2 and macronutrient system parameters in the environments of the Black Sea and the Southern Ocean reveal processes and complex linkages between biogeochemical cycles and their influence on the large-scale global carbon budget. The utilization and the remineralization of macronutrients and carbon yields stoichiometric ratios dependant upon environmental conditions. In the oxic/anoxic environment of the Black Sea, H2S concentrations in the highly stratified water column are affected by the lateral injection of oxidants in Bosporus plume waters. The lateral injection of oxygen in the upper region of the anoxic zone is the primary mechanism of oxidizing H2S, resulting in the observed variation in the stoichiometry between the upper and lower anoxic zones. The determination of macronutrient concentrations permits the inclusion of these minor bases in alkalinity calculations and thus is an improved determination of the carbonate system. Nutrient utilization in the Southern Ocean directly relates to the efficiency of the biological pump. Primary production enhanced by iron addition is manifested as a decrease in the partial pressures of CO2 and a drawdown of macronutrients in the surface ocean. The observed stoichiometric utilization ratios of carbon and macronutrients under iron replete conditions in the low Si(OH)4 concentrations of the Subantarctic and the high Si(OH)4 concentrations differ from each other and classical Redfield values. Variation in the DeltaC:DeltaN stoichiometric ratios in the Southern Ocean ecosystems under conditions of elevated aeolian iron deposition could considerably enhance the flux of atmospheric CO2 into the deep oceans.


Biogeochemistry; Geochemistry

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