Aeration as a Strategy for the Mitigation of Cyanobacterial Blooms: A closer look at the behavior of Microcystis aeruginosa

This study examines the short-term vertical redistribution of Microcystis aeruginosa under controlled conditions, focusing on the combined effects of light attenuation, thermal gradients, and low-energy wind-powered aeration. Laboratory experiments were conducted in a stratified tank system designed to simulate simplified mixing processes in lakes and reservoirs. Following biomass introduction, light penetration decreased markedly, with reductions of 23% at the surface and 83.7% in deeper layers due to biomass concentration. Under unstratified conditions, cyanobacterial biomass accumulated primarily at depths of 40–60 cm above the tank bottom. However, the establishment of thermal gradients induced biomass consolidation at depth between (30–50 cm), corresponding to a temperature range of 18–19 °C which is the same temperature interval that was seen in unstratified conditions. Mechanical aeration weakened the vertical temperature gradient and induced a further upward redistribution of biomass toward the surface, showing a clear physical control on buoyancy-driven positioning. Mechanical aeration significantly redistributed the biomass, leading to a 106.4% increase at the surface while reducing concentrations in the previously stable mid-layers by up to 27.3%, effectively disrupting the thermal gradient–induced niche of M. aeruginosa. Overall, aeration destabilized the vertical biomass structure by neutralizing thermal stability and shifting depth preferences. These findings demonstrate that low-energy, renewable-powered mixing effectively counteracts cyanobacterial buoyancy, providing mechanistic evidence that aeration can disrupt bloom formation.