Compensatory growth in Microcystis aeruginosa after moderate high-temperature exposure

This study aimed to investigate the mechanisms involved in Microcystis aeruginosa (M. aeruginosa) compensatory growth after moderate high-temperature stress. In the experiment, M. aeruginosa were cultured for 3, 6, and 12 d at 35°C before being transferred to normal conditions (25°C), and then cultured for 30 days for recovery. The algae that were cultured constantly at 25°C were set as control. The results showed that the growth of M. aeruginosa was inhibited significantly by the moderate high-temperature stress. During the recovery phase, the M. aeruginosa cultured at 35°C for 3, 6, and 12 days exhibited under-compensation, over-compensation, and equal-compensation, respectively. To cope with moderate high-temperature stress, M. aeruginosa implement various mechanisms, including increasing antioxidant enzyme activities and chlorophyll a content; adjusting compatible solutes (soluble protein and sugar). The M. aeruginosa cultured at 35°C for 6 days has higher antioxidant enzyme activities, relatively low malondialdehyde content, and higher soluble sugar content during the recovery phase; therefore, M. aeruginosa cultured at 35°C for 6 days exhibited over-compensation growth. Grey correlation analysis revealed that the increase of chlorophyll a, soluble sugar, and superoxide dismutase activity play key roles in the compensatory growth of M. aeruginosa.