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 ۱۲:۱۲, ۸:۱۶ and ۱۶:۸ hours dark: light, light intensity of ۳۰۰۰, ۵۰۰۰ and ۷۰۰۰ lux and nitrate levels of ۱.۴۷, ۲.۹۴ and ۴.۴۱ mmol/l were set up. Algae culture was performed at ۲۸±۲ °C in BBM culture medium. Algae cells were counted every three days for one month. By the end of experiments the lowest cell concentration (۹۳×۱۰۵ cell/l) was observed at ۱۲:۱۲ photoperiod, ۱.۴۷ mmol/l nitrate and ۳۰۰۰ lux light intensity and the highest cell concentration at ۸:۱۶ photoperiod, ۲.۹۷ mmol/l nitrate and ۳۰۰۰ 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 (۱.۳۸ gr.) was observed at ۱۲:۱۲ photoperiod, ۳۰۰۰ lux light intensity and ۱.۴۷ mmol/l nitrate levels while the highest biomass (۵.۲ gr.) at ۸:۱۶ photoperiod, ۷۰۰۰ lux light intensity of and ۲.۹۴ mmol/l nitrate level.

Keywords:

Scenedesmus dimorphus , light intensity , photoperiod , growth rate , fatty acids