Abstract

Aquatic systems in an urban environment are subjected to massive anthropogenic nutrient input in the form of either non-point (stormwater) sources or point sources (industry, sewage). Most of these water bodies progress from low-productivity or oligotrophic settings to productive mesotrophic conditions to overenriched eutrophic or hypertrophic conditions. The response to the so-called “cultural” eutrophication is excessive production of undesirable algae and aquatic weeds and oxygen shortages caused by their senescence and decomposition. Cyanobacterial (blue-green) algal blooms have become a serious water-quality problem around the world. From a human perspective it is desirable to prevent or minimize such processes for both aesthetic and health reasons. Algal blooms lower drinking water quality by production of often odorous and toxic compounds; the toxins produced in many blue-green algae have caused health problems for wildlife, livestock, pets, and humans in contact with contaminated water. Given the variety of uses of urban water bodies for recreation, housing development, fish farming, and nature reserves, management guidelines and increasing awareness are urgently needed. The objectives of this entry are to give a short introduction to freshwater blue-green algae, the key environmental factors that lead to their proliferation, and the subsequent environmental problems and to present management strategies.