Ecosystem response to solar ultraviolet-B radiation: influence of trophic-level interactions.

Solar ultraviolet radiation (UVR) can reduce the photosynthesis and growth of benthic diatom communities in shallow freshwater. Nevertheless, greater amounts of algae accumulate in UVR-exposed habitats than in UVR-protected environments. Near-ultraviolet (UVA wavelengths of 320 to 400 nanometers) and mid-ultraviolet (UVB, wavelengths of 280 to 320 nanometers) radiation also inhibit algal consumers (Diptera: Chironomidae). Larval chironomids are more sensitive to UVB than sympatric algae. Differential sensitivity to UVB between algae and herbivores contributes to counterintuitive increases in algae in habitats exposed to UVB. These mesocosm experiments illustrate that predictions of the response of entire ecosystems to elevated UVB cannot be made on single trophic-level assessments.