Coccolith distribution patterns in surface sediments of Equatorial and Southeastern Pacific Ocean

This study aims to contribute to a more detailed knowledge of the biogeography of coccolithophores in the Equatorial and Southeastern Pacific Ocean. Census data of fossil coccoliths are presented in a suite of core-top sediment samples from 15 degrees N to 50.6 degrees S and from 71 degrees W to 93 degrees W. Following standard preparation of smear slides, a total of 19 taxa. are recognized in light microscopy and their relative abundances are determined for 134 surface sediment samples. Considering the multivariate character of oceanic conditions and their effects on phytoplankton, it Factor Analysis was performed and three factors were retained. Factor 1, dominated by Florisphaera profunda and Gephyrocapsa oceanica, includes samples located under warm water masses and indicates the occurrence of calcite dissolution in the water column in the area offshore Chile. Factor 2 is related to cold, low-salinity surface-water masses front the Chilean upwelling, and is dominated by Emiliania huxleyi. Gephyrocapsa sp. < 3 mu m, Coccolithus pelagicus and Gephyrocapsa muellerae. Factor 3 is linked to more saline, coastal upwelling areas where Calcidiscus leptoporus and Helicosphaera carteri are the dominant species. (C) 2009 Elsevier Masson SAS. All rights reserved.