The temporal and spatial variation in morphospecies, size and viability of Microcystis colonies in Lake Taihu

Microcystis has been the dominant bloom-forming cyanobacterial population in Lake Taihu over the past two decades. To illustrate the temporal and spatial variation in the main colony characteristics for Microcystis and their key environmental factors in Lake Taihu, an annual investigation of the size, morphospecies and viability (the viable cell rate) of Microcystis colonies was performed in this study from 2020 to 2021. The average colony diameter ranged from 81.12 to 499.54 mu m at all sites during this investigation. The average colony diameter of the whole lake in spring and in late autumn to early winter was higher than that in other times. Microcystis flos-quae, Microcystis aeruginosa, Microcystis novacekii and Microcystis wesenbergii were the main dominant morphotypes, which was mainly affected by pH, TDP and temperature. Although no significant correlation was found between colony viability and environmental factors, the temporal difference in colony viability was remarkable. Colony viability in autumn (mainly October and November), spring (March and April), and July was lower than that in other times.