Effects of Mn~(2+) on the Growth of Microcystis aeruginosa and Uptake of Nnutrients

Mn is one of the essential trace elements for algae growth,and it functions in many physiological aspects in algae cell.However,effects of Mn on the growth of Microcystis aeruginosa were rarely studied.In this study,the biomass,chlorophyll a concentration of Microcystis aeruginosa and uptake of N,P and Mg during incubation were measured under six different Mn2+ concentrations in culture medium(0,10,100,1000,10 000,30 000 nmol/L).Results showed that the optimum Mn2+ concentration in medium for algae growth was 100 nmol/L,in which the highest biomass was obtained.In treatment of 30 000 nmol /L,the growth of algae was severely inhibited and the biomass was the lowest.Similar trend was observed for the concentration of chlorophyll a.No significant impacts of Mn2+ on the uptake of N were found in this study.However,the uptake of P by the algae responded strongly to Mn2+concentration,and the reduction of P concentration in culture medium treated with 100 nmol/L was 5 times than with 30 000 nmol/L.High concentration of Mn2+ in culture medium also inhibited Mg2+ uptake by algae.