Nutrient‐limited growth of Microcystis aeruginosa and Phormidium tenue and competition under various N:P supply ratios and temperatures

The blue‐green algae Microcystis aeruginosa and Phormidium tenue were grown in nutrient‐limited continuous cultures and together in mixed continuous cultures under various N:P supply ratios and temperatures. The Droop model accurately described the growth of these two algae. Competitive abilities for P and N distinctively differed among these two algae. In competition experiments, M. aeruginosa was the superior competitor under conditions of low N: P supply ratio and high temperature, whereas P. tenue was superior under conditions of high N : P supply ratio and low temperature, which corresponded to field observations of the algal community in Lake Kasumigaura. Both laboratory and field observations suggest that the N: P supply ratio and temperature are significant environmental factors affecting the relative abundances of M. aeruginosa and P. tenue.