Distribution of modern coccolithophore assemblages in the southwest Indian Ocean off southern Africa

Abstract. Living coccolithophore assemblages were investigated in 35 surface water samples taken from the Natal Valley (southwest Indian Ocean) in January and November, 1983 and February, 1984. Fifty-nine species were recognised using a scanning electron microscope (S.E.M.). Cluster analysis revealed four different species assemblages dominated by Emiliania huxleyi, Umbilicosphaera hulburtiana, Umbellosphaera tenuis and Gephyrocapsa oceanica. Significant differences in species composition between the sampling periods are attributed to seasonal fluctuations. The regional distribution of the assemblages reflects two different océanographic regimes: 1) The Agulhas Current, which is a nearly stable feature and 2) the area of the Agulhas Return Current, characterised by rapidly changing hydrographic and ecological conditions.