Proposal Abstract:
Preliminary dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) data indicate that Phaeocystis antarctica plays an important role in carbon and sulfur cycling in the Ross Sea. High sediment DMSP and DMS concentrations, coupled with deep (> 400m) fluorescence peaks, suggest that the carbon export flux associated with Phaeocystis blooms may be significantly underestimated. The Phaeocystis-associated carbon flux to deep water also may have important implications for the glacial iron hypothesis. For example, if silicate depletion in the subantarctic zone occurred, then enhanced eolian iron deposition during the last glacial maximum may have preferentially stimulated Phaeocystis populations. Phaeocystis blooms in the marginal ice zone may sequester carbon and promoted a decrease in atmospheric pCO2. The proposed research will measure DMS and DMSP concentrations in the water column, sediments and in the atmosphere of the Ross Sea as part of the ROAVERRS project. In particular, we propose to determine the significance of Phaeocystis blooms in the Ross Sea to carbon and sulfur fluxes to deep water and to the benthos. Phytoplankton species composition will be compared to DMS dynamics and to DMSP fluxes to the sediments. In addition, the cycling of DMS and DMSP, and the relationship between DMS production/consumption and atmospheric concentrations will be examined