Phytoplankton is defined as free‐floating unicells and colonies that grow photo‐autotrophically in aquatic environments. Phytoplankton plays a key role in the primary production and global elemental cycles of the Earth.

Keywords: algae; cyanobacteria; chlorophyll; primary production; food webs; protists

Figure 1.

Ocean phytoplankton distribution as seen from the SeaWifs satellite. (a) Average map of chlorophyll concentration between September 1997 and August 2000 (Image from (b) Coccolithophorid bloom (arrows) in the English Channel on June 4, 2001 (Image from

Figure 2.

A few phytoplankton species. (a) The diatom Skeletonema costatum under bright field (left) and epifluorescence microscopy (right), revealing the red fluorescence of chlorophyll. (b) The dinoflagellate Alexandrium tamarense. (c) The prymnesiophyte Emiliania huxleyi. The picoplanktonic cyanobacteria Synechococcus (d) and Prochlorococcus (e) Bar, (a, b) 10 µm, (c) 1 µm (d, e) 0.5 µm. Panels (c) reproduced from Riebesell et al. (2000) Nature 407: 364–367 (d)–(e) from Chisholm et al. Nature 334: 340–343.

Figure 3.

(a) Schematic vertical distribution of phytoplankton in the open ocean. (b) Some of the key phytoplankton types and some of the factors involved in their control. No attempt has been made to link a given type of phytoplankton to a given factor as many of the relationships are still not clear.



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Further Reading

Andersen RA (2005) Algal Culturing Techniques. New York: Academic Press.

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Tomas CR (1997) Identifying Marine Phytoplankton. San Diego: Academic Press.

van den Hoek C, Mann D and Jahns H (1995) Algae: An Introduction to Phycology. Cambridge: Cambridge University Press.

Web sites Plankton* Net, a taxonomic resource for phytoplankton: http://e‐bck.rd.awi‐

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Vaulot, Daniel(Apr 2006) Phytoplankton. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0004306]