The southern ocean maintains a moderate, but patchy, biological productivity in spite of harsh environmental conditions (low temperature, extended periods of constant darkness, deep vertical mixing of surface waters). Primary production in coastal Antarctic ecosystems is characterized by an intensive spring bloom which is initiated by a simultaneous increase in water column stability and availability of solar radiation. The duration of the bloom is generally less than 2-3 months, during which time the coastal Antarctic ecosystem receives approximately 70-90% of its annual organic carbon production. The net effect of this temporal pulse of fixed carbon is to increase biological productivity at all trophic levels, from bacteria to baleen whales. However, the precise pathways of carbon transfer, and the rates and mechanisms involved therein have not been carefully investigated. In particular, the role of microheterotrophs in Antarctic foodwebs and the immediate fate of phytoplankton production need to be elucidated. As part of the RACER (Research on Antarctic Coastal Ecosystem Rates) program, this project will evaluate several ecological predictions based upon central working hypotheses which relate physical characteristics of the water column to the temporal pulse of biological productivity. Research efforts will attempt to define the mechanisms, pathways and rates of coupling between photoautotrophic and heterotrophic populations and to evaluate the coupling between the pelagic and benthic habitats. The data obtained during this expedition will add to an overall understanding of the rates of primary and secondary production, and will ultimately be used to formulate a general model of carbon and energy flow in Antarctic coastal ecosystems.
