Species in photograph: Microcystis aeruginosa. Occurrence of the bloom-forming freshwater cyanobacterium Microcystis aeruginosa in lakes, reservoirs, and slowly flowing rivers poses serious social and ecological concerns, with excessive growth typically deteriorating water quality and jeopardizing human and ecological health . Microcystin-LR crosses the blood–testis barrier and interferes with DNA damage repair pathway and also increases expression of the proto-oncogenes, genes involved in the response to DNA damage, cell cycle arrest, and apoptosis in testis. Description: Colonial species. Dead or dying algae form a thick blue-green scum on the water's surface, and release the toxic principle, microcystins. 164 Algae proliferate in shallow, stagnant water, especially in hot, dry weather. Family: Microsystaceae. Click on the illustration to enlarge. Ingestion of toxin-producing blue-green algae (Microcystis aeruginosa) is a rare cause of hepatotoxicity and ALF in dogs. Order: Chroococcales.

Microcystis aeruginosa displays a range of variability in buoyancy in response to light which is dependent upon the previous nutrient or light history of the cell. Colonies tend to float near the surface in nutrient-rich fresh water and other low-salinity waters.