Toxic Effects of Pollutants on Plankton

There are four main sources of aquatic pollution: industrial wastes, municipal wastes, agricultural run-off, and accidental spillage. Non-point sources, such as automobile exhausts, add appreciable amounts of pollutants to air that may enter aquatic systems in rainfall or dry fall-out. These sources add pesticides, heavy metals, oil, petroleum products, and a large number of organic and inorganic compounds to water. Lakesand oceans serveas sinks for many pollutants. Plankton comprise a large portion of the living matter in natural waters and function in biogeochemical cycles. They are affected by pollutants, transfer them to sediments and other organisms,and function in their biologicaltransformation. In natural waters, such as oceans, lakes, rivers, and swampsthe greatest amount of biological production is done by the smallest organisms, the plankton. These microscopic plants and animals comprise communities that drift aimlessly with tides and currents, yet they incorporate and cycle large amounts of energy that they pass on to higher trophic levels.Thus communities of plankton, as distinct as those of swamp, forest, or grassland, support other communities of aquatic species and man. In this chapter, pollution is considered as it affects plankton communities and species. Plankton (Gr. 'wandering') is a general term for those organismsthat drift or swim feebly in the surface water of ponds, lakes, streams, rivers, estuaries, and oceans. It is composed of organismswith chlorophyll (phytoplankton) and animals (zooplankton). Phytoplankton is the primary producer community and consists mainly of algae such as diatoms, dinoflagellates, and a variety of forms from other divisions of the plant kingdom. The zooplankton contains consumer species from