The Effect of Temperature on the Growth Rate of Euglena gracilis

  • Sami Ko
  • Sarah Speckmaier
  • Nancy Wang


Climate change is linked to a rise in global temperatures, which affects many organisms that are sensitive to these changes. The objective of our study was to investigate the effect of temperature on the growth rate of Euglena gracilis. We measured the growth of E. gracilis populations through daily cell counts, across treatments of 13°C (n = 3), 20°C (n = 3), 25°C (n= 3), and 30°C (n = 3), for 11 days. From a one-way ANOVA (p = 2.81*10-10, F3,8 = 812.77) and a Tukey-Kramer test, we found that growth rate significantly differed between the treatments. In order of lowest to highest, the mean growth rates were 0.13/day, 0.23/day, 0.26/day, and 0.27/day for the treatments of 13°C, 20°C, 30°C, and 25°C, respectively. Our results support our alternative hypothesis that temperature does have an effect on the growth rate of E. gracilis, and we were able to reject the null hypothesis that temperature does not affect their growth rate. These findings have implications for global change biology, as changing water temperatures will affect the growth and reproduction of E. gracilis, which will result in alterations to food webs in the ecosystems in which it plays a role.

Keywords: Euglena gracilis, algae, temperature, growth rate, cell division