Temperature effects on growth and buoyancy of Microcystis aeruginosa

Batch cultures of Microcystis aeruginosa (M. aeruginosa) were cultivated at seven different temperatures to measure the specific growth rate at each temperature. A relationship between temperature and specific growth rate was established. We propose a cardinal temperature model for M. aeruginosa with the inflection point (optimal temperature) located at 27.5°C. The model describes 98% of the variability of experimental data from 5°C to 35°C. A digital inline holographic microscope was employed to visualize and analyze the buoyancy of the M. aeruginosa colonies at two different temperatures. The results demonstrated a five times difference in buoyant velocities of colonies at 17.5°C and 28°C. A model was derived to calculate the density of a colony using the buoyant velocity and colony size. The findings provide a better understanding of temperature effects on the growth and buoyancy of M. aeruginosa. The results could facilitate the prediction and mitigation of harmful algal blooms in aquatic ecosystems.