The effect of increasing zinc concentration on the growth rate of Chlamydomonas reinhardtii

Abstract

Zinc is an essential nutrient required by organisms to survive, however, it can be toxic at high concentrations. Since zinc is also a common water pollutant, the objective of this study was to determine how increasing zinc concentration affects the growth rate of a common unicellular green alga species, Chlamydomonas reinhardtii. The experiment was conducted by exposing equal concentrations of C. reinhardtii cells to four different zinc concentrations (4.0 mg/L, 6.4 mg/L, 7.0 mg/L, and 10.0 mg/L) to see how this would influence their growth over time. Over a two week period we periodically counted the number of cells from our samples to see if there was a change in growth rate. Using a one-way ANOVA analysis we found the p-value to be less than 0.05, which supports our alternate hypothesis that increasing zinc concentration would increase the growth rate of C. reinhardtii. However, at our highest zinc concentration of 10.0 mg/L, a decline in growth was observed, therefore we were unable to support our alternate hypothesis. We proposed between 7.0 mg/L to 10.0 mg/L a toxic threshold concentration was reached, resulting in the decline in growth rate.