The Effect of Zn and Mn on the Toxicity of Cd to the Green Microalga Desmodesmus armatus Cultured at Ambient and Elevated (2%) CO_2 Concentrations

摘要

A medium modified by 4-fold (Zn) or 2.5-fold (Mn) decreased/increased content of these metals did not influence the growth of the green microalga Desmodesmus armatus cultured for 24 h at ambient and elevated (2%) CO_2, as compared with original BBM medium (Zn~(21) = 2 mg/L, Mn~2 = 0.4 mg/L). The 4-fold increased content of Zn in the medium markedly enhanced the toxicity of CdCl_2 applied at a concentration (16.8 mg/L) corresponding to EC_(50/24h). The 2.5-fold increase of Mn content reduced the inhibitory effect of Cd on the oxygen evolution rate and F_V/F_M. At low CO_2, Cd did not affect the oxygen evolution but markedly stimulated the activity of carbonic anhydrase (CA). At elevated CO_2, the rate of oxygen evolution was reduced by Cd, whereas CA activity remained unaffected.