The influence of pH on cadmium toxicity to the green alga Stichococcus bacillaris and on the cadmium forms present in the culture medium.

Cadmium toxicity to the green alga Stichococcus bacillaris was investigated in media of pH 3-9. A significant decrease of cadmium toxicity occurred in both the acidic and alkaline ranges of pH. In media of pH 3 and 9, cadmium did not affect the dry mass content substantially. Maximum toxicity of cadmium was noticed at pH 6-7. Voltametric investigations showed a significant effect of pH on electrochemically measured cadmium content in the culture media. Hydrolysis of the medium components and formation of cadmium complexes with OH(-) ions caused a considerable decrease in amounts of electrochemically measured cadmium in the alkaline range of pH.