Photoperiod and light intensity effects on growth and utilization of nutrients by the aquaculture feed microalga, Tetraselmis chui (PLY429)

Light intensity, day length, and nutrient concentrations are important factors regulating the growth of phytoplankton. To reduce culturing costs, natural sunlight and greenhouses can be used to minimize the amount of artificial light needed for algal growth. However, with natural sunlight there is much more variation in the light intensity and the day length than what would be found in a controlled laboratory environment. This study investigated how different light intensities and day lengths affect the growth and nutrient uptake of Tetraselmis chui (strain PLY429)-an algal strain used widely as an aquaculture feed. PLY429 was grown aseptically for 28 days under three different light intensities (220, 110, and 73 μEinst. m−2 s−1) and four different light:dark cycles (24:0, 16:8; 12:12; 8:16). Growth and net nutrient-uptake rates for PLY429 were calculated for each treatment. Longer day length and higher light intensities resulted in higher biomass production and complete utilization of nitrate and phosphate in less time, as compared with shorter days and lower intensities. PLY429 cultures that were exposed to only 8 h of light had the slowest growth and utilization of nutrients. These findings suggest that day length is important in determining growth and nutrient uptake in PLY429; at a latitude of 41°N, artificial light will need to be added to algal cultures in a greenhouse to increase both day length and total daily light input.