Impact of bimetallic combinations of Cu, Ni and Fe on growth rate, uptake of nitrate and ammonium, 14CO2 fixation, nitrate reductase and urease activity of Chlorella vulgaris.

The toxicity of Cu, Ni and Fe individually, as well as in combination (Cu + Ni, Cu + Fe, Ni + Fe), on growth-rate depression, uptake of NO3- and NH4+, photosynthesis, nitrate reductase and urease activity of Chlorella vulgaris has been studied. All the test metals when used individually showed pronounced toxicity on all the parameters studied. However, their interactive effect was mostly antagonistic except for Cu + Ni (synergism). Pre-addition of Fe offered more protection to the cells against copper and nickel toxicity. The data of statistical analysis reconfirmed that 14CO2 uptake is the most sensitive parameter (significant at P less than 0.005, both for time and treatment) than others in metal toxicity assessment. However, these results suggest further that exposure time and sequence of metal addition are very important in biomonitoring of heavy metal toxicity.