Effects of Altered Light Cycles on the Growth Rate of E.gracilis

Abstract

This study was intended to investigate the effect of varying light/dark cycles on the growth and reproduction efficiency of the Euglena gracilis algae; based on the hypothesis that if E. gracilis require different survival strategies to grow their population in light compared to in darkness and it costs them time and energy to switch between these survival strategies, they will reproduce more efficiently when exposed to longer periods of light and darkness. To test this hypothesis, E. gracilis cultures would be exposed to three treatments: a 6-hour light cycle (6 hours of light followed by 6 hours of darkness), a 12-hour light cycle, and a 24-hour light cycle. Additionally, there would be a control group with no light exposure. However, due to unforeseen circumstances, the experiment could not be carried out as planned—alternative treatment cycles consisted of: 6 hours light with 18 hours darkness, 12 hours light with 12 hours darkness, and 24 hours light with 0 hours darkness (the control group remained unaffected by this change). During the growth of the samples, haemocytometer measurements were taken to calculate the population density at each point in time. It was found that the cultures subjected to the 12-hour light cycle exhibited the highest growth rates compared to the other groups. These findings neither support nor reject the original hypothesis due to the differences between the proposed experiment and the one that was actually carried out.