SEASONAL-CHANGES IN COCCOLITHOPHORE DENSITIES IN THE SOUTHERN CALIFORNIA BIGHT DURING 1991-1992

Seasonal changes in coccolithophore cell densities in the San Pedro Ba sin, Southern California Eight, were investigated for the period Octob er 1991 to September 1992. Coccolithophore cell densities ranged from 6.3 x 10(4) coccospheres per liter in March 1992 to 0 cells per liter in November 1991. High coccolithophore concentrations occurred in late winter and spring, and low densities occurred in the summer and fall. The high coccolithophore densities during spring 1992 were associated with unusually low surface nutrient concentrations and a lack of upwe lling, suggesting that the high densities were not part of a typical s pring phytoplankton bloom in this region. We propose that the suppress ion of upwelling during spring 1992 may have been related to the preva iling ENSO conditions. Emiliania huxleyi type 4 dominated the total co ccolithophore population throughout the year, Umbilicosphaera sibogae var. sibogae being the second most important contributor to the coccol ithophore assemblages.