The effects of varying ultraviolet-B radiation on algal growth of Douglas Lake in northern lower Michigan

Abstract

As UV radiation (UVR) continues to rise along with increased ozone depletion, how UVR affects primary producers is of concern. In this study, we examined the effects of UVR on algal biomass (measured by chlorophyll content) and species diversity. Algae were colonized for 12 days on a clear plexiglass grid, floating near the boat dock of Douglas Lake, Michigan. Three treatments were applied: one was UV-filtering, one received natural UVR, and one daily received 90 seconds of elevated UV-B at a wavelength of 365 nanometers. At the end of the experiment, plates were scraped and samples were analyzed for chlorophyll content and algal species biodiversity. A one-way ANOVA of chlorophyll content yielded a p-value of 0.149, meaning that we cannot reject our null hypothesis that UV-B radiation has no effect on algal growth and any observed differences are due to sampling error. Algal cell counts showed that differences in UV levels may affect the type and number of species present. Trends show a slight positive correlation between chlorophyll content and UVR. These results indicate that, with increased ozone depletion, and therefore elevated UV, no change will be observed in the first trophic level of aquatic environments.