Effects of enhanced ultraviolet-B radiation on the production of lipid, polysaccharide and protein in three freshwater algal species

1. The effects of ultraviolet-B (UVB-enhanced) radiation on the production of photosynthates (Lipid, protein, polysaccharide and low molecular weight compounds) was examined for three species of algae. Cryptomonas sp., Nitzschia palea and Synechococcus elongatus were selected as representatives of the Cryptophyceae, Bacilliarophyceae and Cyanobacteria, respectively. 2. Laboratory experiments were performed at several UVBweighted dose rates ranging from 0.018 to 0.391 mW cm(-2). These dose rates span the range of dose rates used in other studies. 3. Effects on the overall photosynthetic rate were observed, even at relatively low UVBweighted dose rates (0.047 mW cm(-2)). 4. The effect of UVB radiation on the fixation of carbon into the main macromolecular pools differed depending not only on the dosage but on the species examined. However, the observed inhibitory effects were generally non-stochastic. In addition, within each species there were differences in the apparent sensitivity of the various fractions to inhibition by UVB radiation. 5. These results suggest that exposure to UVB radiation has the potential to alter the relative allocation of recently fixed carbon to lipid, protein, polysaccharide and low molecular weight compounds in algae in a species-specific manner.