Role of divalent metals Cu2+ and Zn2+ in Microcystis aeruginosa proliferation and production of toxic microcystins

Cu 2+ and Zn 2+ , two ubiquitous metals in water environments, can widely trigger algae blooms at favourable environmental conditions. This paper elucidates the roles of Cu 2+ and Zn 2+ in the proliferation of Microcystis aeruginosa ( M. aeruginosa ) and synthesis of Microcystins (MCs). Findings indicate significant influences of increasing Cu 2+ and Zn 2+ concentrations on cell proliferation at limited available phosphorus concentrations of less than 0.1 mg/L. By contrast, Cu 2+ and Zn 2+ notably affected MCs production at all the inoculated phosphorus concentrations. The critical concentrations of 1 μg/L and 5 μg/L for Cu 2+ and Zn 2+ , respectively, are determined to trigger rapid cell proliferation and MCs production. Furthermore, the impacts of Cu 2+ and Zn 2+ on nitrogen absorption and, subsequently, on amino acids (AAs) formation in cells, is likely key in MCs synthesis. The two AAs Alanine (Ala) and glutamic acid (Glu) demonstrate the most notable variations with the concentrations of Cu 2+ & Zn 2+ .