Coccolithophore. Coloured scanning electron micrograph (SEM) of Emiliana huxleyi. This small algal organism is a calcareous phytoplankton and is surrounded by a skeleton (coccosphere) of calcium carbonate plates (coccoliths). When the organism dies, the plates separate and sink to the ocean floor. Coccolithophores are of particular interest to those studying global climate change because as ocean acidity increases, their coccoliths may become even more important as a carbon sink (absorb carbon dioxide). Individual plates have been found in vast numbers and can make up the major component of a particular rock, such as the chalk of England. E. huxleyi an important part of the planktonic base of a large proportion of marine food webs. Magnification: x6000 when printed at 10 centimetres wide. Specimen courtesy of Mike Allen, Plymouth Marine Laboratory.