Distribution of coccoliths in surface sediments of the south-eastern South Atlantic Ocean: ecology, preservation and carbonate contribution Babette Boeckel * , Karl-Heinz Baumann Universita ¨t Bremen, Fachbereich 5-Geowissenschaften, Postfach 330 440, D-28334, Bremen, Germany Received 20 December 2001; received in revised form 17 November 2003; accepted 17 January 2004 Abstract Recent coccoliths from 52 surface sediment samples recovered from the south-eastern South Atlantic were examined qualitatively and quantitatively in order to assess the controlling mechanisms for their distribution patterns, such as ecological and preservational factors, and their role as carbonate producers. Total coccolith abundances range from 0.2 to 39.9 coccoliths  10 9 g  1 sediment. Four assemblages can be delineated by their coccolith content characterising the northern Benguela, the middle to southern Benguela, the Walvis Ridge and the deeper water. Distinctions are based on multivariate ordination techniques applied on the relative abundances of the most abundant taxa, Emiliania huxleyi, Calcidiscus leptoporus, Gephyrocapsa spp., Coccolithus pelagicus and subtropical to tropical species. The coccolith distribution seems to be temperature and nutrient controlled co-varying with the seaward extension of the upwelling filament zone in the Benguela. A preservation index (CEXV ) based on the differential dissolution behaviour of the delicate E. huxleyi and Gephyrocapsa ericsonii versus the robust C. leptoporus is applied in order to detect the position of the coccolith lysocline. Although some samples were recognised as dissolution-affected, the distribution of the coccoliths in the surface-sediments reflects the different oceanographic surface-water conditions. Mass estimations of the coccolith carbonate reveal coccoliths to be only minor contributors to the carbonate preserved in the surface sediments. The mean computed coccolith carbonate content is 17 wt.%, equivalent to a mean contribution of 23% to the bulk carbonate. D 2004 Elsevier B.V. All rights reserved. Keywords: coccoliths; coccolith carbonate; ecology; South Atlantic; surface sediments 1. Introduction A major oceanic feature in the south-eastern South Atlantic Ocean is the Benguela upwelling system. It belongs to one of the major eastern boundary upwell- ing systems of the world. Favouring enhanced primary productivity it acts as a substantial CO 2 sink. By means of the biological pump primary producers, such as coccolithophores, contribute to the possibly cli- mate-relevant transfer of carbon from surface waters to the deep ocean. Coccolithophores not only thrive abundantly in the photic zone of oligotrophic water-masses, but also constitute a considerable part of the phytoplankton community in high productivity regions. Seasonally high proportions of coccolithophores have previously been reported from upwelling areas (Mitchell-Innes 0377-8398/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.marmicro.2004.01.001 * Corresponding author. E-mail address: bboeckel@uni-bremen.de (B. Boeckel). www.elsevier.com/locate/marmicro Marine Micropaleontology 51 (2004) 301 – 320