Primary productivity and the silica cycle in the Southern Ocean (Atlantic sector)

Tentative data for the biogenic silica production in a section along 10°E are calculated from the dissolved silica distribution. North of a sharp silica front, found south of the Antarctic Polar Front and near the Maud Rise production was relatively high. These areas have also high bottom relief, causing redistribution of sediments as is demonstrated from 210Pb analyses. This overestimates the importance of such areas in budget calculations of the accumulation of biogenic silica. Dissolved silica concentrations in interstitial waters are highly variable, low values are explained by the incorporation of Al in diatom frustules. Dissolution in the surface sediments is 3 times larger than burial; this is more than previously assumed. Calculations of the flux out of the sediments from gradients in interstitial waters and in bottom waters, using diffusion coefficients determined from 222Rn profiles give reasonable agreement.