Cadmium and chromium toxicity to pseudokirchneriella subcapitata and microcystis aeruginosa

Abstract

The toxicity of cadmium and chromium to Pseudokirchneriella subcapitata and Microcystis aeruginosa was evaluated through algal growth rate during 96h exposure bioassays. Free metal ion concentrations were obtained using MINEQL + 4.61 and used for IC50 determination. Metal accumulations by the microorganisms were determined and they were found to be dependent on the concentration of Cd2+ and Cr6+. IC50 for P. subcapitata were 0.60 μmol L -1 free Cd 2+ and 20 μmol L -1 free Cr 6+, while the IC50 values for M. aeruginosa were 0.01 μmol L -1 Cd 2+ and 11.07 μmol L -1 Cr 6+. P. subcapitata accumulated higher metal concentrations (0.001 - 0.05 μmol Cd mg -1 dry wt. and 0.001 - 0.04 μmol Cr mg -1 dry wt) than the cyanobacteria (0.001 - 0.01 μmol Cd mg -1 dry wt and 0.001 - 0.02 μmol Cr mg -1 dry wt). Cadmium was more toxic than chromium to both the microorganisms.