Assessment of synergistic interactions between environmental factors on Microcystis aeruginosa growth and microcystin production

The combined effect of four abiotic factors on Microcystis aeruginosa growth and toxin production was assessed by culturing the cyanobacterium under different light intensities (10-190 μmol photons·m− 2·s− 1), CO2 concentrations (0-10% (v/v)), temperatures (15-40 °C), and pH values (6.5-9.5). Results indicate a significant influence caused by the synergistic effect of environmental factors over growth-related parameters and cyanobacteria toxicity. The combined use of low to medium light intensities (50-120 μmol photons·m− 2·s− 1) and CO2 concentration (1-6% v/v) led to higher cell concentrations, while specific growth rate and biomass productivity were favoured by medium to high light intensities (110-190 μmol photons·m− 2·s− 1), CO2 concentrations (4-9.5% v/v) and temperatures (29-39 °C). Regarding microcystin (MC) production, higher concentrations were obtained at low light intensities and low CO2 concentrations while approximately 2000-fold lower MC concentrations were achieved by simultaneous use of high values of light intensity, CO2 concentration and temperature.