Coccolith contribution to carbonate sedimentation during El Niño events in the Santa Barbara Basin (California).

Coccolithophores provide a good index of environmental conditions because they are primary producers in the photic zone and they are directly dependent on temperature, salinity, and nutrients. Moreover, coccolithophores play a significant role in the global carbon and carbonate cycles. Comparisons of living communities from sediment trap samples with assemblages preserved in surface sediment are important for knowledge of climatic effects on coccolithophores, their contribution to total carbonate flux and for paleoceanographic applications. This comparison allows recording the hydrographic changes in the upper water column, particularly in relation to El Nino (EN) events. El Niño is a disruption of the ocean-atmosphere system in the tropical Pacific that has important consequences for global weather patterns. The EN events were defined by two indexes: Multivariate ENSO Index (MEI) from 1996 to 1950 and Southern Oscillation Index (SOI) from 1950 to 1939. The aim of this study is to monitor and understand the response of coccolithophorid carbonate export production to EN events in varved sediment of the Santa Barbara Basin (SBB, 34º 19’N; 120º 02’W) recovered during the last 60 years. Particularly, we will discuss the total coccolith versus the total carbonate fluxes and the fine sediment fraction elemental composition during EN and non-EN events. In this study, we have observed an increase of coccolithophore flux in the years following EN events. In particular, G. oceanica shows a strong positive correlation with strong EN event like 1965-66, 1982-83 and 1997-98. The 1997-98 EN event recorded in the varved sediments will be also compared with sediment trap coccolithophore fluxes in the center of SBB. We will also discuss the possible relations between coccolith increases and some minor chemical element (Fe, Zn,) changes in the surface water column.