The rapid increase in populations of algae and other phytoplankton, in particular cyanobacteria, that occurs in inland water systems, such as lakes. The density of the organisms may be such that it may prevent light from passing to lower depths in the water system. Algal blooms are caused by an increase in levels of nitrate, a mineral ion essential for algal and bacterial growth. The source of increased nitrate may be from agricultural fertilizers, which are leached into water systems from the land, or sewage effluent. Algal blooms contribute to the eutrophication of water systems. See also eutrophic. Compare red tide.
Subjects: Biological Sciences — Environmental Science.