Effects of Mixed Allelochemicals on the Growth of <i>Microcystis aeruginosa</i>, Microcystin Production, Extracellular Polymeric Substances, and Water Quality

Abstract

The inhibition of cyanobacteria growth by allelochemicals, which controls harmful algal blooms has been examined in many studies. The objective of this work was to compare the efficiencies of different allelochemicals and determine a mixing proportion corresponding to the highest algae inhibiting activity and smallest adverse effect. The obtained results demonstrated that artemisinin, nonanoic acid, malonic acid, and ethyl acetate inhibited algal growth more efficiently than D-menthol and lactic acid. Synergies were observed in five groups of allelochemical combinations with inhibition ratios exceeding 80%, and the concentrations of extracellular microcystin-LR in the groups with high algal inhibition ratios were lower than that in the control group on the 7th day. No changes in extracellular polymeric substances compositions were detected after treatment. The permanganate indices of the treated groups were higher than that of the control group; however, this disparity gradually decreased with time. In addition, a sharp decrease in the concentration of dissolved inorganic phosphorus was observed for all treated groups. From the obtained data, the optimal proportion of mixed allelochemicals corresponding to 3.94 mg L−1 of artemisinin, 6.27 mg L−1 of nonanoic acid, 8.2 mg L−1 of malonic acid, and 6.38 mg L−1 of ethyl acetate was suggested.

Keywords

• allelochemical mixture
• algae inhibition
• Microcystin leucine arginine (MC-LR)
• extracellular polymeric substance (EPS)
• permanganate index (PI)
• dissolved inorganic phosphorus (DIP)