Temperature-dependent dominance of Microcystis (Cyanophyceae) species: M. aeruginosa and M. wesenbergii

The effect of water temperature on the succession of the two Microcystis species, M. aeruginosa and M. wesenbergii, was examined through field and laboratory studies. In the eutrophic Furuike Pond, seasonal successions of Microcystis species and related environmental parameters were investigated between May and November 2006. Microcystis aeruginosa was more abundant than M. wesenbergii in June, August to early October and M. wesenbergii was more abundant in July and between late October and November. The water temperatures during the dominance of M. aeruginosa were relatively higher (from 24.7 to 33.9 degrees C) than those during the dominance of M. wesenbergii (from 19.6 to 28.6 degrees C). In the laboratory experiments where each Microcystis species was cultured under various temperatures, growth rates of M. aeruginosa were significantly higher than those of M. wesenbergii at high temperatures (30 and 35 degrees C). However, growth rates of the two species were similar at lower temperatures (20 and 25 degrees C). Consequently, water temperature changes during summer may be an important environmental factor for the alternating succession of Microcystis species.