Biogeography of selected Holocene coccoliths in the Atlantic Ocean

Abstract

In this chapter we present a revision of the biogeographical distribution of five coccolithophorid species (Coccolithus pelagicus, Calcidiscus leptoporus, Heli-cosphaera carteri, Syracosphaera pulchra and Umbilicosphaera sibogae) and the genus Gephyrocapsa in the Atlantic Ocean. The mapping is based on surface sediment samples. Each of the taxa considered here constitutes an unambiguous morphological group ideal for rapid low taxonomic resolution analysis of assemblages, which is a tempting strategy for ecological and paleoecological analysis of assemblages. However, in each case recent research has indicated that these broad taxa are in fact composed of several discrete species, or sub-species. The clearest example is C. pelagicus, with discrete morphotypes in sub-Arctic and temperate upwelling areas. For Gephyrocapsa and Umbilicosphaera the separation is less obvious but still unambiguous. Species separation is manifestly essential to understanding the biogeography of these taxa. For H. carteri and S. pulchra the mapped distributions are relatively straightforward and we do not yet know how they relate to the recently proven genotypic variation within the taxa.