BIOGENIC SILICA FLUXES AND ACCUMULATION RATES IN THE GULF OF CALIFORNIA

The Gulf of California, though small in size, plays an important role in the global silica cycle. The seasonal pattern of biogenic silica fl ux in the gulf is closely related to that of phytoplankton biomass lev els and is controlled by changes in weather and hydrographic condition s. The highest opal fluxes (approximately 0.35 g.m-2.d-1) occur during winter and spring, and they are comparable to those measured in some of the most productive ecosystems of the world. Approximately 15%-25% of the biogenic silica produced in surface waters is preserved in gulf sediments, a figure significantly higher than the average global ocea n preservation rate. However, the flux of opal at 500 m water depth is less than 25% of that being produced at the surface, suggesting that most of the recycling of biogenic silica in the Gulf of California occ urs in the upper water column.