Nickel uptake and toxicity in cyanobacteria

This study reports the toxicity of nickel to Anacystis nidulans and Spirulina platensis grown in artificial culture medium and also the accumulation of this metal by these cyanobacteria. The two species were treated with different concentrations of Ni as NiSO4 5H2O. Growth rate, carbon assimilation (C14) and chlorophyll‐A content were the parameters measured for toxicity. Both species showed significant reduction in growth rates with increasing concentrations of the metal. In the case of A. nidulans 0.1 ppm Ni resulted in a significant reduction, while at this concentration S. platensis had a hormetic effect. Chlorophyll‐A content of and carbon assimilation by these cyanobacteria were negatively correlated with Ni concentration. However, the rate of decrease varied with the species. Carbon assimilation was inhibited more than chlorophyll‐A content, as indicated by assimilation efficiency, i.e., the ratio between carbon assimilation and chlorophyll‐A content. In the case of metal accumulation the concentration factor was negatively correlated with metal concentration in the medium.