Effect Of Radiation On The Primary Productivity Of Phytoplankton In Lake Taihu

The effects of light radiation on the phytoplankton were different in species, which due to the mechanisms of phytoplankton counteracting the irradiance. In this study, we researched the effects of light radiation on the primary productivity of phytoplankton. It included three parts:(1) Comparing the vertical distribution of primary productivity in Lake Wnli and Mailiang Bay of Lake Taihu. Results showed that on the water surface, the primary productivity of phytoplankton in the Lake Wuli was lower than that in the Mailiang Bay. The simulation experiment indicated that the phytoplankton in the Mailiang Bay was more resistant to high-intensity radiation. According to the phytoplankton species compositions, we found that Mailiang Bay was dominated by the Cyanobacterium Microcystis spp..(2) A novel device OXYM/5 had been used to determinate the photosynthetic oxygen production of phytoplankton dominated by Microcystis sp. from Lake Taihu, cultured Microcystis sp. (separated from Lake Taihu) and Scenedesmus sp. under the artificial solar radiation. The results demonstrated that the Microcystis sp. was more resistant to UV-B radiation than Scenedesmus sp.and contained a large amount of MAAs. The cultured Microcystis sp. failed to endure the low-wavelength radiation of high-intensity. All of the algae had showed a reaction time to light irradiance, and the photoinhibition was closely related to the duration of exposure.(3) Recults also indicated that UV radiation had significant impact on the concentrations of MAAs in Anabaena sp., and the amount of MAAs increased with the duration of exposure of UV radiation.Judging from the responses of different algae to solar and artificial radiation, the synthesis of MAAs in Microcystis sp. and Anabaena sp. could be one of the adaptive strategies to high solar radiation including UVR and one of the bloom-forming mechanism.