Cyanobacterial growth is favored in ponds and lakes where waters are calm and have little turbulent mixing. Their life cycles are disrupted when the water naturally or artificially mixes from churning currents caused by the flowing water of streams or the churning water of fountains. For this reason blooms of cyanobacteria seldom occur in rivers unless the water is flowing slowly. Growth is also favored at higher temperatures which enable "Microcystis" species to outcompete diatoms and green algae, and potentially allow development of toxins.