Effects of copper and zinc on Microcystic aeruginosa growth and microcystins production

The cyanobacteria bloom is one of typical manifestations of eutrophication, yet the effects of heavy metals entering water on cyanobacteria bloom remain unclear. In the present study, the effects of copper and zinc ions on the growth of Microcystic aeruginosa (M. aeruginosa) and the production of microcystins (MCs) were investigated. The results showed that a Cu2+ concentration of 0.02 mg/L stimulated the growth of M. aeruginosa, while growth inhibition occurred at a Cu2+ concentration of 0.1 mg/L. The maximum value of MC-LR (167.74 μg/L) occurred at a Cu2+ concentration of 0.02 mg/L. In contrast, a Zn2+ concentration of 0.1 mg/L stimulated the growth of M. aeruginosa, whereas growth inhibition was observed at a Zn2+ concentration of 0.5 mg/L. The maximum MC-LR value of 130 μg/L appeared under control conditions. Moreover, the production of MC-LR increased as the growth of M. aeruginosa was inhibited with a Cu2+ concentration of 0.1 mg/L, whereas the production of MC-LR decreased as the growth of M. aeruginosa was stimulated with a Zn2+ concentration of 0.1 mg/L, compared to their respective controls.