Seasonal variations in the morphology of the coccolithophore Calcidiscus leptoporus off Bermuda (N. Atlantic)

Coccolithophores are a group of marine unicellular planktonic algae, member of the Haptophyta, producing calcite platelets (coccoliths) surrounding the cell. Coccoliths are major contributors to deep-sea carbonate sediments and have a well-documented fossil record dating back to the Triassic. The use of observation of changes in the morphological characteristics of the coccoliths evolving through time has constituted a major biostratigraphic tool The composition of coccolith assemblages has also been used for paleoceanographic reconstructions (McIntyre et al., 1970). However, one important limitation on the use of coccolith assemblage composition for paleoceanographic studies is the different dissolution rates in the water column and sediments depending on species. In order to avoid this possible bias in the composition of the assemblage observed in the sediments, further attempts to obtain useful information for paleoceanographic reconstructions from coccoliths have been based on morphological variations of a single species, or of a complex of species. Several morphometric studies of coccolithophore species have revealed a high degree of coccolith morphological variability that could be related to environmental parameters and be the result of either genetic variability or ecophenotypy