Abstract: Microalgae are the potential resources for producing biological and renewable energy. In this study, two microalgae Oocystis solitaria and Selenastrum sp. were collected from a coastal freshwater pond, and a culture experiment was conducted to determine the optimum water temperature, light intensity, and water salinity for the growth and reproduction of the two microalgae. The cellular biochemical composition of the two microalgae was analyzed, and the effects of water salinity on the lipid content of these microalgae were investigated. The suitable water temperature and light intensity for the growth of O. solitaria and Selenastrum sp.were 35.9-40.5 ℃ and 29.7-32.8 ℃, and 46-70 μmol·m^-2·s^- and 17-54 μmol·m^-2·s^-, respectively. O. solitaria grew best in fresh water, while Selenastrum sp. flourished in brackish water at salinity 2. Under suitable culture conditions, the cell protein, carbohydrate,and total lipid contents of O. solitaria were 27.61%, 22.00%, and 3.84%, respectively, and those of Selenastrum sp. were 28.06%, 21.99% and 12.53%, respectively. In the fatty acid of O. solitaria, 18:3n3 was abundant; while in that of Selenastrum sp., DHA presented. Water salinity affected the total lipid content of the two microalgae. At salinity 4 and 10, O. solitaria and Selenastrum sp. had the highest lipid content, being 8.29% and 18.21%, respectively.

Key words: controlled release fertilizer, summer maize, N release, nutrients uptake.