EFFECT OF DISSOLVED METAL ION CONCENTRATION ON TOXIN PRODUCTION OF FRESHWATER CYANOBACTERIA

Abstract

 In this study, we investigated the effect of metal induced oxidative stress on the production of microcystin via the field surveys of lakes dominant with cyanobacteria and laboratory incubation tests. The 16s rRNA gene analysis indicated that the microbial communities are dominated by Microcystis aeruginosa. Measured water quality parameters including chlorophyll a and microcystin per cell number as well as metal concentrations were analyzed by principal component analysis as well as correlation analysis, indicating the relation of microcystin per cell number with metal concentrations such as Ca and Mg. The incubational study using Microcystis aeruginosa (PCC7806 strain) consistently indicated that higher heavy metal (Cu and Zn) concentrations and lower Mg concentrations induced higher oxidative stress and toxin production. These results suggest that it is necessary to focus on the concentration of multiple metals that affect oxidative stress in order to clarify the cause of toxic cyanobacteria in closed waters.