Climate control of biological UV exposure in polar and alpine aquatic ecosystems

Abstract

The severe depletion of stratospheric ozone in Antarctica over the last two decades has generated much concern about the effects of rising UV-B radiation on marine and freshwater ecosystems (de Mora et al. 2000; Cockell and Blaustein 2001; Sommaruga 2001; Hessen 2002; Perin and Lean 2004) and has led to a broad range of research on UV optics, photobiology and photochemistry in the aquatic environment. The studies to date imply that certain ecosystem types may be especially prone to major changes in their spectral UV regime: clear lakes and oceans in the polar regions where ozone depletion is occurring and where UV wavelengths penetrate deeply into the water column (Vincent and Belzile 2003), and oligotrophic alpine waters which have little UV-screening protection because of their low concentrations of colored dissolved organic matter (CDOM; Morris et al 1995; Williamson et al. 1996; Laurion et al. 2000; Markager and Vincent 2000). The biological communities in these ecosystems may also be more vulnerable to UV toxicity because of the inhibiting effects of cold temperatures on cellular repair of UV damage (Rae et al. 2000; Hoffman et al. 2003; MacFadyen et al. 2004). The UV waveband is a highly reactive component of all environments exposed to the sun, and is subject to large fluctuations at multiple timescales. It is increasingly apparent that climate may exert a strong control on these fluctuations, and that the amplitude of such effects can be much greater than those caused by moderate stratospheric ozone depletion. Major shifts in underwater UV are likely to accompany future climate change, with implications for many important photobiological and photochemical processes in the aquatic environment.