Abstract: In this study, five species of microalgae (Chlorococcumsp.SHOU-F3, Ankistrodesmus sp. SHOU-F33, Chlorellasp.SHOU-F46, Coelastrum sphaericumSHOU-F10, and Scenedesmus sp. SHOU-FX) were isolated from freshwater, and a culture experiment was conducted to determine the optimal water temperature and light intensity for the five microalgae. The biochemical compositions of these microalgae were also analyzed. For the Chlorococcumsp. SHOU-F3,Ankistrodesmus sp. SHOU-F33, Chlorellasp. SHOU-F46, C. sphaericum SHOU-F10, and Scenedesmus sp. SHOU-FX, the optimal water temperature was 29.8, 23.5, 31.4, 34.4, and 24.7 ℃, and the optimal light intensity was 16, 119, 42, 82, and 106 umol·m^-2·s^-1, respectively. Under the suitable culture conditions, Chlorococcum sp. SHOU-F3 cells had the highest contents of pigments, protein, and carbohydrates, while Ankistrodesmus sp. SHOU-F33 cells had the highest content of total lipid.

Key words: temperate grassland, bacterial diversity, bacterial community structure, nitrogen deposition, precipitation.