The cycles of biogenic elements in the Ross Sea are unusual in a number of respects when compared to other oceanic regions. For example, the seasonal cycle of primary productivity appears to be dominated by ice- edge phytoplankton blooms which are controlled by the spatial extent of the meltwater produced by the receding ice. This bloom is highly dependent on nitrate as a nitrogen source, and hence large amounts of the bloom's production is available for export. The Ross Sea, and the western portion in particular, is also the site of extensive deposits of siliceous sediments, and accumulation rates are the highest measured in the world's oceans. The diatomaceous component of the sediments also is the same species which dominates the ice-edge phytoplankton bloom. However, the sediments are not enriched in organic matter to the same extent that they are in silica, and material collected in sediments traps also appears to be enriched with silica relative to organic matter. This proposal seeks to investigate the production, vertical flux, water column regeneration, and sediment accumulation rates in the western Ross Sea in order not only to quantify these rates at one location, but also to understand the mechanisms controlling the apparent uncoupling of organic and siliceous matter cycles. This project is one component of a coordinated interdisciplinary study in the Ross Sea Results from this study will document the apparently unique coupling between the surface production and the accumulation in the sediments, and will help clarify the reasons for the differences in the cycles of organic and siliceous particulate matter. Information obtained will also greatly assist global models of production and sedimentation of biogenic material.
