Abstract:In order to evaluate the effects of critical environmental factors on growth of Cylindrospermopsis raciborskii, the growth of two strains isolated from Zhenhai Reservoir in Guangdong Province was studied under combining temperature from 12℃ to 32℃ and irradiance (from 30 to 120 µmol m-2s-1) and three nitrogen sources (nitrate-N, ammonium-N and urea-N). The result showed that the growth of N1 and N8 strains of C. raciborskii increased with temperature under three light conditions and their growth rate was the biggest at 28℃ with high irradiance. Cylindrospermopsis raciborskii N1 strain was not able to grow at both 12℃ and 16℃, while N8 strain only could not be at 12℃. These suggested that the strain N8 had higher tolerance to low temperature than N1. The strains N1 and N8 grew well under nitrate-N (2-247 mg L-1), but only at a low level of ammonium-N and urea-N. Moreover, the growth of both strains completely inhibited under high ammonium-N and urea-N (128-247 mg L-1). The specific growth rates of N1 strain under three nitrogen sources were always higher than those of N8 strain, which indicated that the capability for strain N1 to utilize nitrogen was stronger than strain N8. In conclusion, Cylindrospermopsis raciborskii isolated from Guangdong Province has high strain diversity and adapt to high temperatures and a wide range of light intensities, and is able to use multisource of nitrogen. This may be the reason for frequent occurrence of C. raciborskii in the studied region.