Algicidal activity of Aspergillus niger induced by calcium ion as signal molecule on Microcystis aeruginosa

Abstract Cyanobacterial blooms pose great threats to water environment safety and human health due to the release of microcystins, and flocculation is an effective way to control cyanobacterial blooms. In this study, Aspergillus niger 7806F3 exhibited high flocculation activity on Microcystis aeruginosa species, and the addition of calcium ion could cause lysis of algal cells. Meanwhile, the combined effect of strain 7806F3 and calcium ion was conducive to reducing extracellular microcystins. The supernatant of strain 7806F3 induced by calcium ion possessed algicidal activity, which could be inhibited by calcium/calmodulin dependent protein kinase (CaMK) inhibitor, suggesting that calcium ion, as signal molecules, can activate CaMK activity, thus regulating a series of algicidal activities. The disturbance induced by 7806F3 and calcium ion on the bacterial community was not obvious, which indicated that the algicidal activity of Aspergillus niger induced by calcium ion cannot significantly affect the bacterial community dynamics. All these results confirm for the first time that calcium ion, as signal molecules, induce the algicidal activity of Aspergillus niger, which can provide a novel choice for controlling cyanobacterial blooms.