Plankton, Status and Role of

“Plankton” is a collective term for organisms adapted specifically for a life in suspension in the open waters (the pelagic zone) of the sea and of such inland waters as lakes, reservoirs, and rivers. Planktonic organisms include protists, microorganisms, and certain types of small metazoan animals, all sharing a common liability to passive entrainment in water currents, generated by tide, wind, convection, gravity, and the rotation of the earth. The physical variability of open-water habitats typically favors short life histories; rapid changes in dominant species composition, in response to fluctuating environmental conditions, contribute to the maintenance of high biological diversity in individual habitats and to the survival of high species richness among planktonic assemblages in general. This article provides an overview on form, function, and selection of the main plankton groups and discusses temporal patterns in the organization, diversity and species richness of planktonic communities in the aquatic environment and its habitat types.