Effect of Light Exposure on the Growth Rate of Euglena gracilis

Abstract

This study aims to investigate the effect of different lengths of light exposure on the growth of Euglena gracilis. E. gracilis is an important part of the ecosystem as they are essential in providing nutrients for the salmon in Salish Creek. Longer lengths of daily light exposure were predicted to increase the growth rate of E. gracilis. To test this prediction, E. gracilis was exposed to three treatments with various lengths of light exposure (no light cycle, 8-hour light cycle, full light cycle). Cell count of each treatment sample was recorded over a ten-day period. The ANOVA test results showed a relationship between daily length of light exposure and the growth rate of E. gracilis. As a result, we reject the null hypothesis. Thus, longer light exposure would result in increased growth of E. gracilis. The major source of error in our experiment stems from the usage of different microscopes and micrometers in the process of cell-counting and not leaving a few days in the initial period for the lag phase of the cells. Additional uncertainties and limitations such as inconsistent incubator light intensities may have also affected the growth of E. gracilis.