Chlamydomonas reinhardtii and salinity: the effects of NaCl on population growth.

Abstract

Salinity is an important abiotic variable prevalent in aquatic habitats and can have an effect on population growth, including that of algae. The effect of salinity on the population growth of Chlamydomonas reinhardtii was investigated using NaCl. The null hypothesis assumes that as salt concentration increases the growth of C.reinhardtii will remain the same as initial cell concentration. One alternative hypothesis is that as salinity increases the growth of the organism decreases. Lastly, our other alternative hypothesis states that as salinity increases so will the growth of the organism. We grew C. reinhardtii under four different NaCl concentrations (0µM, 100µM, 150µM, and 200 µM), taking samples six times non-consecutively over a period of two weeks. At the end of the two weeks, we used a haemocytometer to count cells. For our analysis, we performed a two-way ANOVA on the cell count data after two weeks to determine whether the differences in growth due to increased salinity was significant. we found that the effect of salinity on growth is significantly different in our control group which experienced exponential growth (p= 6.373 x 10^-14, at 0.05 significance level). For 100µM concentration, some significant growth was observed for specific treatments while for both 150µM and 200µM concentrations, no significant growth occurred. The data suggests that C. reinhardtii can grow in very little salt concentration, but exponential growth only occurs in the absence of NaCl. The implications of the experiment are discussed.