Oxygen Consumption and Isotope Fractionation in Marine Phytoplankton

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Todd M. KanaIOS - 0727488Oxygen consumption and isotope fractionation in marine phytoplankton.Phytoplankton use oxygen for both photosynthesis and respiration. Oxygen use in photosynthesis directly effects the efficiency of carbon uptake, and therefore it has an important impact on measures of primary production. This research focuses on oxygen use in phytoplankton by two poorly understood processes, alternative respiration and chlororespiration. Alternative respiration and chlororespiration have the potential to use a significant amount of available energy without providing the benefit of growth substances produced by photosynthesis, particularly in brightly lit waters. In addition, alternative respiration has recently been identified as a process that may have a significant effect on the oxygen isotope composition of natural waters. It is hypothesized that chlororespiration may also contribute to the isotopic signature in marine waters. This project will use stable isotope measurements and physiological characterizations of oxygen uptake in phytoplankton, including the cyanobacterium Synechococcus, the dinoflagellate, Prorocentrum minimum, and the diatom, Skeletonema costatum, among others. The experimental work will provide information on the occurrence and activity of chlororespiration and alternative respiration under various environmental conditions. The results of this work will provide critical information for improving estimates of photosynthesis (productivity) in the oceans. In addition, the stable isotope data aid in the interpretation of oxygen isotope data that are used for paleoclimatology (historical temperature records) and estimates of the balance of primary and secondary production (autotrophy and heterptrophy) at the global scale. This project will include secondary school teachers as summer research assistants through the Environmental Science Education Partnership, and will include graduate student training.