Effects of cobalt and pH on the growth of Chlamydomonas reinhardtii

The effects of up to 50 ppm cobalt nitrate at pH 2-12 on the growth of Chlamydomonas reinhardtii were studied in cultures at 20-22C for 21 d. The eukaryotic chlorophyte was chosen for its relative genetic complexity. The organism was able to grow in the pH range 4-12; it exhibited a buffering mechanism which resulted in final pH values of 8.3-9.8. An initial pH of 8 was chosen for the metal toxicity experiments. Some growth occurred at 20 ppm cobalt(II) but 10 ppm had no effect. At 30 ppm and above, the metal was lethal and no resistance developed during the experiment.