How does pH impact the growth of Chlamydomonas reinhardtii?

  • Gurkim Grewal
  • Rachael Kim
  • Sally Mason-Newton


Ocean acidification impacts various marine species, including salmon. In order to understand the ecological effects of ocean and river acidification on salmon, it is essential to understand its effects on Chlamydomonas reinhardtii, as it is a primary producer in the salmon food chain.
This study examined the impact of pH variation on the growth of C. reinhardtii. The experiment was conducted over a period of 11 days. On four set days, 10 μL of a fixative, iodine potassium iodide (IKI), was added to 100 μL samples containing C. reinhardtii from an acidic, basic, and control treatment. The number of cells per mL were counted on the last day using a hemocytometer and a compound microscope. The results show that the C. reinhardtii population increased from 2.0 x 10^5 cells/mL to 4.18 x 10^5 cells/mL in the basic medium of pH 8 and decreased to 0.46 x 10^5 cells/mL in the acidic medium of pH 5. Statistical analysis using a
two-way analysis of variance (ANOVA) showed that the organism’s growth between treatments was significant and that there is an interaction between the pH levels and time at p < .05, while the difference in growth over time was not significant at p < .05.