Calcereous Nanoplankton

Tiny minute golden brown algae 15-100 um in diameter make up this group. During one stage they secrete platelets of calcite called coccoliths; these coccoliths interlock to form an external skeleton called the coccosphere which surrounds the living cell. They are extremely abundant in the marine sediments and are routinely used in studies of paleoclimatology (the study of ancient oceans) and biostratigraphy (the study of the temporal and spatial distribution of fossil organisms in sediments). The White Cliffs of Dover and blackboard chalk are composed of coccoliths.