The effect of mineral oil on the CO₂ concentration of Chlamydomonas reinhardtii’s environment over time

Oil is a common water pollutant that is released into the environment through spills which can harm marine ecosystems. As oil spreads out over the water surface, the diffusion of CO₂—which is required by Chlamydomonas reinhardtii for photosynthesis—becomes inhibited. This experiment investigated the effect of mineral oil on the CO₂ concentration of C. reinhardtii’s environment. We performed titrations on samples of C. reinhardtii that we treated with mineral oil to find the concentration of CO₂. The control group had the greatest change in CO₂ concentration over time, while the full oil treatment had the lowest. The mean CO₂ concentrations were 77.83 ppm for the control group, 53.67 ppm for the partial treatment, 49.08 ppm the half treatment, and 44.42 ppm for the full treatment. A two-way ANOVA revealed our results to be statistically significant for both time (p=2.9 x 10-4), treatment (p=6.0 x 10-5) and the interaction between the two (2.2 x 10-16); thus, we all three null hypotheses. It is possible that the metabolic rates of C. reinhardtii were reduced due to the toxicity of aromatic hydrocarbons found in oil, although there was some growth over the 7-day period of the experiment.