Long-term acclimation to warming improves the adaptive ability of Microcystis aeruginosa to high temperature: Based on growth, photosynthetic activity, and microcystin production.

Gradually warming of water bodies caused by climate change is expected to intensify the expansion of Microcystis blooms causing a series of severe problems in waters. However, most predictions about global warming further promoting the dominance of Microcystis are dependent on the strains only experiencing short-term acclimation to high temperature. It still remains unknown whether long-term warming acclimation improves the adaptive ability of Microcystis to high temperature. The present study used Microcysits aeruginosa maintained at 25 °C, short- and long -term acclimated at 30 °C to explore the above knowledge gaps. The results showed that: (1) The growth rate of long-term warming acclimated M. aeruginosa was significantly enhanced, compared with those of low temperature cultured and short-term warming acclimated ones; (2) A faster decline rate of photosynthetic activity during growth phase and a higher ultimately stable photosynthetic activity during stationary phase of M. aeruginosa were caused by longer warming acclimation time; (3) high temperature reduced the microcystin production of long-term warming acclimated M. aeruginosa compared to that of low temperature cultured M. aeruginosa; (4) Warming acclimation time improved the driving effect of photosynthetic activity on the growth of M. aeruginosa but decreased the restriction ability of growth state to microcystin production of M. aeruginosa at high temperature; (5) Compared to low temperature cultured M. aeruginosa, high temperature improved the driving effect of photosynthetic activity on the growth of long-term warming acclimated M. aeruginosa, but decreased the sensitivity of photosynthetic activities to environmental resources and the regulative ability of microcystin production to photosynthetic activity. These findings indicated that long-term warming acclimation enhanced M. aeruginosa adaptive ability to high temperature and demonstrated the necessity of applying long-term warming acclimated strains in the future studies about the impact of global warming on cyanobacteria.