EFFECTS OF FLUCTUATING LIGHT ON THE GROWTH OF MICROCYSTIS AERUGINOSA UNDER LOW LIGHT AVERAGE INTENSITY

To study the effects of fluctuating light on algae, the growth of Microcystis aeruginosa, a typical water bloom alga, was studied under different light conditions using an experimental device with a light intensity control system based on a single-chip system. Four light conditions were applied in this research: three fluctuating light groups (10min FL, 1h FL and 6h FL) with different fluctuation cycles and an average light group (AL). The experimental results show that the cell densities of Microcystis aeruginosa in the 6h FL, 1h FL and 10min FL groups were 28.3% (P<0.05), 18.2% (P<0.05) and 7.7 (P>0.05), respectively, which were higher than that in the AL group. It was also found that the specific growth rate, F_v/F_m and rETR of Microcystis aeruginosa in the three fluctuating light groups were significantly higher than those in the AL group (P<0.05), and each index significantly increased with the length of the fluctuating light cycle, but the mean NPQ and carotenoids per unit dry weight showed the opposite relationship to fluctuating light. The results also showed that Microcystis aeruginosa could better regulate their photosynthesis mechanism to utilize light energy under fluctuating light than under constant light when the average light intensity was low, and the longer the fluctuating period was, the better the utilization efficiency. This implies that fluctuating low-intensity light can be used as a means to increase algae production.