Dissertation Research: The Effect of Iron on Silicon, Nitrate and Carbon uptake by Phytoplankton-potential Mechanisms for altered Si:N and Si:C ratios in Diatoms

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Iron plays an important role in the function and productivity of aquatic ecosystems, either directly, via effects on biogeochemistry and nutrient cycling, or indirectly, via effects on plankton community composition. Dr. Brzezinski and Ms. Franck would like to explore the ways in which iron availability can regulate diatom production and macronutrient cycling in the Polar Frontal Zone in the Pacific Sector of the Southern Ocean and in the highly productive upwelling areas off the coast of California and Peru. All are regions where large diatoms blooms and net CO2 drawdown can occur, but where iron (Fe) and silicon (Si) availability may play a role in regulating the timing and occurrence of these blooms and the magnitude of CO2 uptake. In this work the investigators will quantify the effects of Fe availability on Si and nitrate biogeochemistry, as well as look for mechanisms behind the observed effects, e.g. how Fe availability alters Si and nitrate uptake kinetics, diatom species composition and species-specific Si uptake.