Estimates the global rate of biogenic silica production in the ocean to be between 200 and 280 × 1012 mol Si yr-1. The upper limit is derived from information on the primary productivity of the oceans, the relative contribution of diatoms to primary production and diatom Si/C ratios. The lower limit is derived independently using a multi-compartment model of nutrient transport and biogenic particle flux, and field data on the balance between silica production and dissolution in the upper ocean. Incubation experiments indicate that silica production rates exceed the mean by a factor of 3-12 in coastal areas and are 2-4 times less than the global average in the oligotrophic mid-ocean gyres. The mechanisms leading to more efficient opal preservation in regions of silica accumulation are presently unknown, but they have no simple relationship to primary productivity. Regional differences in opal preservation appear to be controlled by factors such as low surface temperature, selective grazing and aggregate formation, which diminish the rate of silica dissolution in surface waters and/or accelerate its transport to the seafloor. -from Authors