Particle fluxes in a coastal upwelling zone: sediment trap results from Santa Barbara Basin, California

Particle fluxes were measured in the center of Santa Barbara Basin on a bi-weekly basis for a three-year period beginning in August 1993. Lithogenic material dominates the total flux throughout the entire year, although it is delivered to the basin primarily during the winter rainy period. It appears that both biological and physical processes control the eventual transport of detrital material to the deep part of the basin. Biogenic sedimentation in Santa Barbara Basin is dominated by opaline silica, with highest fluxes during the spring–summer upwelling period. Export ratios (ratios of organic carbon flux to primary production) are inversely related to primary production. This relationship may be due to increased advective transport and/or enhanced regeneration of organic carbon during the highly productive upwelling period. During the first half of the study period, Santa Barbara Basin was influenced by El Niño conditions and our data suggest that productivity in this region is reduced during such periods. Seasonal changes in the relative contributions of biogenic and lithogenic material to the total particle flux, combined with the lack of bioturbation on the sea floor, results in the accumulation of varved sediments in Santa Barbara Basin.