Solar ultraviolet-B radiation and aquatic primary production: damage, protection, and recovery WARWICK F. VINCENT De'partement de biologie et Centre d'e'tudes nordiques, Universite' Luval, Sainte-Foy (Que'bec), Canada GlK 7P4 AND SUZANNE ROY Institut national de recherche scientifique - Oce'anologie, Rimouski (Qukbec), Canada G5L 3Al Received September 9, 1992 Accepted January 6, 1993 VINCENT, W. F., and ROY, S. 1993. Solar ultraviolet-B radiation and aquatic primary production: damage, protection, and recovery. Environ. Rev. 1: 1- 12. The continuing degradation of the Earth's ozone layer by atmospheric pollutants has generated concern about the impact of increased solar ultraviolet-B radiation (UV-B) on aquatic ecosystems. UV-B is a small (less than 1% of total energy) but highly active component of the solar spectrum that can penetrate to biologically significant depths in lakes and oceans. It has the potential to cause wide-ranging effects, including mutagenesis, chronic depression of key physiological processes, and acute physiological stress that may result in death. There are major uncertainties at present about the appropriate time scales and bioassay protocols for assessing such effects. Algal and cyanobacterial cells have four lines of defence against the toxic effects of UV-B. Some species avoid UV exposure by their choice of habitat or by migration strategies. Many species produce sunscreening pigments that filter out UV wavelengths; mycosporine-like amino acids are an especially impor- tant and ubiquitous class of such compounds. Most cells have a variety of defences against the toxic end products of UV radiation, such as radical scavenging by carotenoid pigments and superoxide dismutase. Finally, most cells have at least some ability to identify and repair the UV damage of DNA and other biomolecules. There is a large interspecific variability in the extent of each of these defence strategies. Continuing ozone depletion is not likely to cause an abrupt collapse of photosyn- thetic production, but may result in subtle, community-level responses that could ultimately impact on higher trophic levels. Key words: Arctic, Antarctic, photosynthesis, UV radiation, UV-B, ozone, atmospheric pollutants. VINCENT, W. F., et ROY,S. 1993. Solar ultraviolet-B radiation and aquatic primary production: damage, protection and recovery. Environ. Rev. 1 : 1-12. La degradation continue de la couche d'ozone de la terre par des polluants atmosphCriques a engendrC une prCoccupation au sujet de I'impact d'une augmentation de la radiation solaire ultraviolette B (UV-B) sur les Ccosystitmes aquatiques. Les UV-B sont un constituant minime (moins de 1 % de I'Cnergie totale), mais hautement actif du spectre solaire qui peut pCnCtrer a des profondeurs significatives dans les lacs et les oceans. 11s ont la capacitC d'entrainer des effets trits divers incluant la mutagknitse, le dkritglement chronique de processus physiologiques fondamentaux, ainsi qu'un stress physiologique aigu qui peut conduire a la mort. I1 y a prdsentement de grandes incertitudes quant aux Cchelles de temps appropriCes et aux protocoles expkrimentaux pour Cvaluer de tels effets. Les cellules des algues et des cyanophycCes montrent quatre lignes de defense contre les effets toxiques des radiations UV-B. Certaines espitces Cvitent I'exposition aux radiations UV en choisissant leur habitat ou en adoptant des stratCgies de migration. Plusieurs espitces produisent des pigments qui agissent comme filtre en Climinant les radiations UV; des acides aminks ressemblant a la mycosporine constituent une classe particulierement impor- tante et ubiquiste de tels composks. La plupart des cellules ont une gamme de dCfenses contre les sous-produits toxiques de I'activitC des UV, tel que 1'Climination des radicaux par les pigments carotCnoi'des et la dismutase superoxyde. Enfin, la plupart des cellules possitdent au moins une certaine capacitC a identifier et a reparer les dommages subis par I'ADN et autres bio-molCcules. 11 existe une importante variabilitC interspecifique dans 1'Ctendue de chacune de ces stratCgies de dCfense. La diminution continuelle de I'ozone ne conduira vraisemblablement pas a une baisse drastique de la production photosynthdtique, mais pourrait se traduire par des rCactions subtiles au niveau des communautCs, suivies de consCquences ultkrieures aux niveaux trophiques supkrieurs . Mots cle's : Arctique, Antarctique, photosynthitse, radiation UV, UV-B, ozone, polluants atmosphCriques. [Traduit par la rCdaction] Introduction to 60% or less now forms across Antarctica each year over a region that is slightly larger than Canada (e.g . , smith et al. There is mounting evidence that the solar flux of ultraviolet- 1992). Reliable measurements of UV radiation did not begin B radiation (UV-B) has begun to rise at certain locations over in Antarctica until 1988, but the observations to date show a the the Earth (Cmtzen l992). This increase has been close, inverse relationship between stratospheric ozone con- attributed to the continuing destruction of the ozone layer by centration and ground-level UV-B. With the annual breakup of atmospheric pollutants, in particular chlorofluorocarbons the Antarctic ozone hole each year, ozone-depleted air spreads (CFCs). Although these pollutants are mainly released from out over the Southern Hemisphere; this has resulted in record- human activities in the Northern Hemisphere, the effects have 10, concentrations of stratospheric ozone over temperate been most clearly identified in the Antarctic region, where a regions such as southern Australia and New Zealand in early unique combination of extreme cold and stratospheric circu- summer (Toon and Turco 1991). lation (the polar vortex) results in conditions that are favour- ~zonede~letion has been more recently reported in the north able for the CFC-ozone reactions (Anderson et a1. 1991). A polar region (Hofmann and Deshler 1991). Model calculations spring "ozone hole" containing ozone concentrations depleted using atmospheric ozone data collected over the period 1979- Pnnted in Canada 1 Imprim6 au Canada