Impact of artificial mixing on colony fragmentation versus aggregation

Determine whether artificial lake mixing systems, specifically bubble plume aeration, enhance bloom-control efficiency by fragmenting Microcystis colonies or instead promote aggregation of Microcystis cells and colonies under operational turbulence levels, by quantifying the net effect on colony size distributions and dynamics.

Background

Artificial mixing (e.g., bubble plumes) is widely used to control cyanobacterial blooms, yet hydrodynamic forcing can both fragment and aggregate colonies. The paper emphasizes that colony size strongly influences buoyancy, light exposure, and bloom persistence, making the net effect of mixing on colony size distributions a critical management question.

Previous studies measured average dissipation rates in mixed systems but did not resolve local stress intensities near fast-moving surfaces where fragmentation is more likely. The authors’ experiments and modeling suggest division-formed colonies resist fragmentation at typical bubble-plume turbulence, while aggregation may occur at high biovolume fractions, leaving the overall net outcome of mixing operations unresolved.