The Vertical Migration Dynamic of Microcystis aeruginosa in a Water Column

The prediction and numerical modeling of cyanobacterial outbreaks have emerged as a significant research topic. Presently, in-situ and remote sensing observations serve as the primary foundation for numerical modeling. Owing to the influence of local environmental factors on fieldwork-based models, cross-sectional comparisons among distinct models remain challenging. In this study, three tanks (height: 1.8m) were installed in the laboratory to represent the structure of vertical zone in shallow lakes, and Microcystis aeruginosa culture was observed under a 12/12 light cycle for one month maintaining constant conditions. The findings indicate that light intensity, duration, and light-dark cycling all impact vertical migration of M. aeruginosa. Microcystis aeruginosa exposed to low light intensities (18 to 39 μmol photons m^-2 s^-1) migrated more rapidly than those under high light intensities (447 to 466 μmol photons m^-2 s^-1); cells subjected to extended illumination (over 8 hours) exhibited stable distribution patterns; and, in darkness, cyanobacteria that were in high light intensity areas responded more swiftly compared to those that were in low light intensity areas. The findings suggest that M. aeruginosa vertical migration is continuous and dynamic, and not vitally light intensity dependent. To effectively conduct cross-sectional comparisons of models across lakes, it is imperative to thoroughly consider the diurnal variation of vertical migration of M. aeruginosa. Based on the research results, recommendations for changes to the current vertical migration numerical model are provided.