Microcystis aeruginosa is a species of freshwater cyanobacteria that can form harmful algal blooms of economic and ecological importance.

[3] As the etymological derivation implies, Microcystis is characterized by small cells (of only a few micrometers diameter), which lack individual sheaths.

The aquatic plant Myriophyllum spicatum produces ellagic, gallic, and pyrogallic acids and (+)-catechin, allelopathic polyphenols inhibiting the growth of M.

[12] In recent years major incidents have occurred in both China[13] and the United States / Canada[14][15][16] M. aeruginosa is the subject of research into the natural production of butylated hydroxytoluene (BHT),[17] an antioxidant, food additive, and industrial chemical.

The dead animals included grazers and browsers, which preferred drinking from the leeward side of two dams, a natural point of accumulation for drifting Microcystis blooms.

The source of nutrients that supported the Microcystis growth was narrowed down to the dung and urine voided in the water by a large resident hippo population, unaffected by the bloom.

[25] In contrast research in Lake Erie has suggested that glyphosate may lead to blooms of another cyanobacterium - Planktothrix - in place of Microcystis.