The Effect of Salinity on the Growth Rate of Tetrahymena thermophila

  • Je Eun (Michelle) Hwang
  • Jayden Kim
  • Srijan Subedi
  • Jobina Tamminga


The objective of our study was to determine the effect of calcium chloride dihydrate (CaCl2∙2H2O) on Tetrahymena thermophila. T. thermophila is a common ciliated protozoan in freshwater and is an important primary producer for many ecosystems. This study measured the growth rate of T. thermophila in 0mM, 2mM, 20mM and 200mM of CaCl2∙2H2O (n=3). Cell concentration was measured in each test tube when first adding the organisms and then after 2, 4, 7, 9, 25 and 28 hours to find the overall growth rate. The results of this experiment showed that the 0mM concentration of salt had the highest average growth rate of 1259 cells/mL/h, followed by 2mM with a growth rate of 1164 cells/mL/h and then 20mM with a growth rate of 758.2 cells/mL/h. The 200mM concentration of salt had a negative growth rate of -186.1 cells/mL/h, with the cell concentration decreasing over time. Using ANOVA and Tukey’s post hoc statistical analysis, it was revealed that the 200mM concentration was significantly different than the other three concentrations of 0mM (p=0.0001), 2mM (p=0.0002), and 20mM (p=0.0023) respectively. The other three concentrations were not significantly different from each other.