The Effects of Cobalt Sulfate on Tetrahymena Thermophila Population Growth Rates


  • Ethan Cheng
  • Anderson Kuo
  • Bryn Murphy
  • Lauren Rutherford


Tetrahymena thermophila is a unicellular eukaryote found in freshwater habitats.
Substances released via anthropogenic activity can have detrimental effects on aquatic species
such as T. thermophila. Specifically, in British Columbia, there are several copper mines that
release cobalt as a major by-product. Cobalt sulfate, a heavy metal, enters the water and binds to
sediment, resulting in harmful effects on aquatic ecosystems. To study these effects on aquatic
organisms, T. thermophila was exposed to three different concentrations of cobalt sulfate (0
mg/L, 9 mg/L, and 11 mg/L). Cell counts were taken after exposure to cobalt sulfate for 1.5, 3.5,
5.5, 7.5, 24, 26.5, and 28.5 hours and were used to determine cell growth rates (cells/mL/hour)
over 28.5 hours. A One-Way ANOVA test was performed, leading us to reject the null
hypothesis that none of the control nor treatment groups are different from each other. Using the
Tukey-Kramer test, it was found that the 11 mg/L treatment was significantly different from the
0 mg/L treatment. Instead of having a negative effect on cell growth rates, the data support the
idea that increasing concentrations might have been beneficial to T. thermophila cell growth.
However, there are many limitations to our study, thus, further research needs to be conducted to
solidify whether cobalt sulfate is beneficial or detrimental towards T. thermophila.