Comparative studies on phosphate utilization of two bloom-forming Microcystis spp. (cyanobacteria) isolated from Lake Taihu (China)

Microcystis is a common freshwater bloom-dominating cyanobacterial genus. However, the crucial factors that affect the seasonal succession and extent of dominance of different species remain largely unknown. This study investigated inorganic phosphorus (P) uptake, growth, and P utilization of two dominant Microcystis species from Lake Taihu (China) at different P concentrations and temperatures. Compared with Microcystis wesenbergii, Microcystis flos-aquae had higher maximum uptake rate and luxury storage coefficient. However, M. flos-aquae also had a higher P demand for growth. Under P-rich conditions (64.5 to 174.5 μM), M. flos-aquae had a higher growth rate (0.16 to 0.21 d^?1) than M. wesenbergii (0.06 to 0.19 d^?1) at 22 to 30 °C. M. wesenbergii, with higher phosphate affinity, had a lower P demand to sustain its growth, and yielded a higher growth rate of 0.10 d^?1 at low P concentration (6.5 μM) at 34 °C, whereas M. flos-aquae had a lower growth rate of 0.03 d^?1. Therefore, M. flos-aquae was dominant in late spring under P-rich conditions, whereas M. wesenbergii prevailed in hot summer after M. flos-aquae decreased under P-limited conditions. These results agree well with their succession patterns in the field. Overall, succession and dominance of M. flos-aquae and M. wesenbergii in Lake Taihu are regulated by P concentration and water temperature.