Biogeochemistry of Carbon and Silicon on the Antarctic Shelf: Particle Flux and Taxonomic Studies

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This project is the renewal of a study of the vertical flux and the rate of dissolution of biogenic silica in the water column of the Ross Sea, and is part of a coordinated study of the biogenic silica and organic carbon cycling in the water column and the sediments of the Ross Sea. The antarctic deep sea and continental shelf environment is the major repository for silica accumulation in the global ocean, and dominates the global silica budget. The Ross Sea is a particularly anomalous area in which large amounts of biogenic silica are accumulating in modern sediments, while the surface production rates are generally below the global average. Moreover the usual similarity between the oceanic silicon and carbon cycle does not appear to hold around Antarctica, and the two cycles are decoupled in that the rate of particulate carbon deposition in the modern sediment is very low. The overall project is an integrated study of the production, vertical transport, dissolution, and deposition processes, using moored instrumentation and direct observations in a series of transects in the Ross Sea by R/V POLAR DUKE, carried out between 1989 and 1991. The vertical flux and dissolution rates were measured by deploying time-series sediment traps at two depths on each of three moorings for a period of fourteen months. In conjunction with transmissometers and current meter arrays, these moorings will allow the measurement and characterization of both vertical and horizontal fluxes of particulate matter during a complete annual cycle of production and sedimentation. The objectives of this renewal are to recover one sediment trap that was redeployed for an additional two years, to complete the analysis of all water column and sediment trap samples that are currently in hand, and to produce a synthesis of all project data sets in cooperation with the other investigators cooperating in this project.