The use of a benign fast-growing cyanobacterial species to control microcystin synthesis from Microcystis aeruginosa

( ), one of the most prevalent blue-green algae in aquatic environments, produces microcystin by causing harmful algal blooms (HAB). This study investigated the combined effects of nutrients and cyanobacterial subpopulation competition on synthesizing microcystin-LR. In varied nitrogen and phosphorus concentrations, cyanobacterial coculture, and algicidal DCMU presence, the growth was monitored by optical density analysis or microscopic counting, and the microcystin production was analyzed using high-performance liquid chromatography-UV. Furthermore, growth and toxin production were predicted using MATLAB. First, coculturing with a fast-growing cyanobacterium Synechococcus elongatus UTEX 2973 ( ) reduced biomass and microcystin production at 30oC. Under high nitrogen and low phosphorus conditions, is mostly effective, with up to 94.7% and 92.4% limitation of growth and toxin synthesis, respectively. Second, this biological strategy became less effective at 23oC, where grew slower. Third, photosynthesis inhibitor DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) hindered growth (at 0.1 mg/L) and microcystin production (at 0.02 mg/L). DCMU was also effective for controlling microcystin production in - cocultures. Based on experimental results, a multi-substrate, multi-species kinetic model was built to describe coculture growth and population interactions. Future research should examine more complex models to further develop and refine to facilitate the derivation of more effective recommendations for health prevention programs, particularly for mothers and girls.