RESPONSES OF DEEP-SEA BENTHIC FORAMINIFERA TO SEASONAL FLUCTUATIONS IN PRODUCTIVITY OF THE SOUTHERN CALIFORNIA MARGIN

Analyses of living (Rose Bengal stained) deep-sea benthic foraminifera collected on the Southern California margin reveal temporal and spatial changes in foraminiferal assemblages that are related to changes in sea-surface productivity. Samples were collected from two sites (water depths of 990 and 1330 m) during the months of August and October 1996. Results show that benthic foraminiferal abundances in the >63 micron fraction and increases in the densities of the 63-150 micron fraction seem to be positively related to surface productivity in this region. However, >150 micron fraction assemblage abundances of this high productivity region are not correlated with surface productivity. Opportunistic taxa, such as Nonionella fragilis, respond quickly to sea-surface productivity blooms. Based on these results, total abundances in the >63 micron fraction, comparisons between the >150 micron and >63 micron fractions, and known opportunistic species should be used in assessing paleoproductivity along productive continental margins.