Effects of UV Radiation on Wetland Periphyton: Algae, Bacteria, and Extracellular Polysaccharides

ABSTRACT

To study the effects of UV radiation on wetland periphyton, glass substrata were placed under acrylic mesocosms in a small freshwater marsh in Michigan, USA. One treatment excluded light in the UV range (<400nm), and another allowed the passage of all light. Substrata were sampled on four dates during August and September 2004. Chlorophyll a, algal community composition, ash-free dry mass, bacterial density and viability, and total extracellular polysaccharide (EPS) content were measured. Algal biomass, algal community composition, bacterial abundance, and ash-free dry mass were relatively insensitive to UV treatment; however, the proportion of non-viable bacteria (p = 0.006) and area-specific EPS content (p = 0.025) were significantly greater in the UV-exposed treatment. These results suggest that ambient levels of UV can damage periphytic bacteria and may cause corresponding functional changes within naturally occurring periphytic communities.