Growth Rate of Euglena Gracilis in Response to Different Incubation Temperatures


  • Jonathan Hao
  • Kaitlyn Le
  • Daniel Lee
  • Henry Payette


Global warming is the world’s largest unsolved problem with rising temperatures
affecting many organisms. As Euglena gracilis is an essential species in the Fraser
River of Vancouver, British Columbia, this study aimed to determine if increasing
temperatures like those predicted to occur due to climate change, has an effect on the
growth rate of E. gracilis. Its growth rate was compared in three treatments
(representing current temperature conditions (20 ºC), predicted temperature conditions
(25 ºC), and a control (30 ºC) based on optimal growth temperatures) with three
replicates per treatment. Over the course of 20 days, eight 20 μl samples were obtained
from each replicate and cells were counted on a haemocytometer grid. Adjusted results
showed that temperature does not affect the growth rate of E. gracilis. It also
contradicted our prediction that the closer the temperature was to 30 ºC, the higher the
growth rate would be. Instead, the highest growth rate was found in the 25 ºC treatment,
followed by the 20 ºC treatment, and lastly the 30 ºC control. This discrepancy may be
due to study errors as cell concentration was not calculated correctly. Overall,
temperature was not found to have a significant effect on the growth rate of E. gracilis,
which is counter to the broader literature.