When UV Meets Fresh Water

Ultraviolet radiation has detrimental and beneficial effects in freshwater ecosystems. Ultraviolet radiation (UV)—the shortest-wavelength, highest-energy solar radiation that passes through the atmosphere—is a potent force affecting life on Earth. Exposure to UV, which reaches Earth's surface at wavelengths between 290 and 400 nm, can damage DNA and impair an organism's ability to reproduce, sense its environment, and resist disease. Ozone concentrated in the stratosphere shields living organisms from the most damaging wavelengths of UV, known as UV-B (280 to 320 nm). In the 1980s and 1990s, observations that this protective layer was becoming depleted, and that a seasonal ozone “hole” over the Antarctic was expanding, generated serious concerns about the potential negative effects of increased UV on aquatic ecosystems (1). More recently, however, it has become clear that even the shortest-wavelength, highest-energy UV reaching Earth has beneficial as well as detrimental effects on individual organisms and thus on natural ecosystems (2).