Studies On The Photosynthetic Characteristicsm Dynamic Growth And Competition Between Microcystis Aeruginosa And Chloromonas Rosae

The effects of temperature, light and pH on photosynthesis of Microcystis aeruginosa (M. aeruginosa) and Chlommonas rosae (C. rosae) were studied by measuring their net photosynthetic O₂ evolution. In this research, five nitrogen (N) and five phosphorous (P) concentrations, which represented gradients from subtrophication to hyper-eutrophication, were examined. Furthermore, five NO₃^- -N/NH₄⁺-N ratio (0%, 25%, 50%, 75%, 100%) were set up to investigate the effects of NO₃-N ratio on photosynthesis and growth rate of the M. aeruginosa and C. rosae. The competition between the two algae was studied by mixed culture under oligotrophic and eutrophication conditions. The results showed that 1.) the net photosynthesis of both algae increased with the temperature, the photosynthesis of M. aeruginosa increased linearly in the range of 10-35 ℃, indicating that its optimum temperature might be higher than 35 ℃; while the photosynthesis of C. rosae decreased dramatically when the temperature was over 30℃. The photosynthesis-light response curves of the two algae were different. The light saturation point (LSP) of M. aeruginosa was around 500 μmol·m^-2·s^-1 and photoinhibition did not occur upon it when the light intensity reached as high as 900 μmol·m^-2·s^-1. On the contrary, the photosynthesis of M. aeruginosa was inhibited when light intensity exceeded its LSP (630 μmol·m^-2· s^-1. The photosynthesis of M. aeruginosa, with the optimum pH of 10.0, was very active and stable in the pH range of 6.5-11.5. The optimal pH of C. rosae was 7.0, any slight departure from the optimal...