Dominance and growth factors of Pseudanabaena sp. in Drinking Water source reservoirs, Southern China

Pseudanabaena sp. is a common and harmful species in freshwater cyanobacteria blooms. There are very few studies on its distribution characteristics and growth influencing factors. In the current study, it was found to be dominant in three cascading reservoirs in Southern China. Field observations and laboratory experiments were integrated to investigate the dominance and growth factors of Pseudanabaena sp. The effects of temperature, light intensity, nutrients, chemical oxygen demand (COD), pH, and disturbance on Pseudanabaena sp. growth were evaluated. The results indicated that Pseudanabaena sp. had significant positive correlations with water temperature, pH, and COD (p < 0.01) and a positive correlation with NH₃^-N (p < 0.05). The optimum growth temperature range for Pseudanabaena sp. was from 20 to 30 °C; hence, it usually has outbreaks in May and August. The optimum light intensity and pH for Pseudanabaena sp. were 27 μmol photons m^-2s^-1 and from 7 to 9, respectively. The superior tolerance for low light, disturbance, and phosphorus deficiency of Pseudanabaena sp. may be the main factors affecting its dominance in reservoirs. Controlling nitrogen was more effective than controlling phosphorus to avoid the risk that was brought by Pseudanabaena sp. This study contributed to the theoretical knowledge for the prediction and control of the growth of Pseudanabaena sp.