Proposal Abstract:
The growing season for phytoplankton in polar oceans is short, but intense. There is an increasing body of evidence that in many Antarctic habitats, the most active period may be very early in the season, a period that has not been emphasized in previous investigations. This project is part of an interdisciplinary program that focuses on the dynamics of the spring phytoplankton bloom in a highly productive subsystem of the Antarctic, the Ross Sea. The overall program will test hypotheses related to the initiation of the phytoplankton bloom shortly after the onset of ice melt, the mechanisms controlling phytoplankton growth and productivity in spring, the implications and short-term fate of high productivity in spring, and the transition from spring to midsummer conditions. This research will investigate the initiation of the phytoplankton spring bloom, especially the factors which may be important in triggering and terminating the Phaeocystis pouchetii bloom. Specific research will focus on sulfur and manganese cycling processes especially with regard to possible global climate change processes. Correlations of particulate and dissolved dimethyl sulfide concentrations will be estimated with respect to phytoplankton pigment concentrations. Phytoplankton growth rates will be assessed using pigment labeling techniques. The fate of the dimethyl sulfide produced will be determined. Measurements will be performed to determine the relative importance of: (a) bacterial uptake (b) fluxes out of the photic zone from sediment trap samples and (c) atmospheric emissions. The effects of acrylic acid production on various components of the food web, such as its bactericidal properties will be investigated. The overall goal of this component is to understand the dynamics of the oceanic sulfur cycle during the spring bloom.