This project is an analysis of the rate of production and dissolution of biogenic silica in the uppermost 150 meters 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 data base for the study was obtained from dedicated cruises of the R/V Polar Duke in 1990 and in 1992. 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 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 analysis phase will concentrate on three sites, identified in the field phase, at which the biogenic silica and organic carbon content differed by two or three orders of magnitude. The objectives of the project are to quantify the variability of silica production and dissolution rates in these sites of silica-rich and silica-poor surface sediments through isotope mass spectrometry of the samples obtained on the 1991-92 cruise, and to produce an integrated surface silica budget that will be combined with vertical flux data and sediment accumulation data to be obtained by the cooperating investigators.
