Effects of light intensity and photoperiod on growth rate and biomass production in green algae Scenedesmus dimorphus

Abstract:; Effects of photoperiod, light intensity and nitrate levels on growth (cell number) and biomass of Scenedesmus dimorphus was studied. Three levels of photoperiod 12:12, 8:16 and 16:8 hours dark: light, light intensity of 3000, 5000 and 7000 lux and nitrate levels of 1.47, 2.94 and 4.41 mmol/l were set up. Algae culture was performed at 28±2 °C in BBM culture medium. Algae cells were counted every three days for one month. By the end of experiments the lowest cell concentration (93×105 cell/l) was observed at 12:12 photoperiod, 1.47 mmol/l nitrate and 3000 lux light intensity and the highest cell concentration at 8:16 photoperiod, 2.97 mmol/l nitrate and 3000 lux light intensity. Increase in photoperiod correlated with significant increase in cell concentration. Higher light intensity with lower nitrate levels resulted in higher cell concentrations. The lowest algal biomass (1.38 gr.) was observed at 12:12 photoperiod, 3000 lux light intensity and 1.47 mmol/l nitrate levels while the highest biomass (5.2 gr.) at 8:16 photoperiod, 7000 lux light intensity of and 2.94 mmol/l nitrate level.