This book offers extensive coverage of the most important aspects of UVR effects on all aquatic (not just freshwater and marine) ecosystems, encompassing UV physics, chemistry, biology and ecology. Comprehensive and up-to-date, UV Effects in Aquatic Organisms and Ecosystems aims to bridge the gap between environmental studies of UVR effects and the broader, traditional fields of ecology, oceanography and limnology. Adopting a synthetic approach, the different sections cover: the physical factors controlling UVR intensity in the atmosphere; the penetration and distribution of solar radiation in natural waters; the main photochemical process affecting natural and anthropogenic substances; and direct and indirect effects on organisms (from viruses, bacteria and algae to invertebrate and vertebrate consumers). Researchers and professionals in environmental chemistry, photochemistry, photobiology and cell and molecular biology will value this book, as will those looking at ozone depletion and global change.

This volume originates from the NATO Advanced Study Institute Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models, held in Pisa, Italy in June 2001. The Institute was sponsored and mainly funded by the NATO Scientific Affairs Division, whose constant contribution in favour of the cooperation among scientists from different countries must be acknowledged. Other Institutions substantially contributed to the success of the ASI and our thanks and appreciation go to the Italian National Research Council (Consiglio Nazionale delle Ricerche), the Italian Space Agency (Agenzia Spaziale Italiana), the European Society for Photobiology and the bank Banca Toscana. In the last two decades of the past century, concern has been growing for the possible effects on the biosphere of the stratospheric ozone depletion, due to anthropogenic emissions of ozone-destroying chemicals. The ozone loss causes an increase in the biologically important part of the solar ultraviolet radiation (UV) reaching the Earth’s surface, which constitutes a threat to the biosphere, because of UV damaging effects on humans, animals and plants. The international agreements have reduced the production of ozo- destroying compounds, which, however, are still present in high concentrations in the stratosphere, mainly because of their longevity, and thus ozone depletion will likely continue for several decades.

Following the rapid developments in the UV-B measurement techniques and the rapidly growing research in the field in the late 80's and early 90's, we organized a large gathering of distinguished experts in a NATO Advanced Study Institute, held in Halkidiki, Greece on October, 2-11. 1995. The Institute was organized so as to include state of the art lectures on most aspects of solar ultraviolet radiation and its effects. This was achieved by extended lectures and discussions given in five sessions by 27 lecturers and a demonstration of filed measurements and calibration techniques at the end of the Institute. The ASI began with the sun and fundamentals on solar radiative emissions and their variability in time and continued with the interaction of solar Ultraviolet with the atmosphere through the complex scattering processes and photochemical reactions involved. Particular emphasis was given to changes in atmospheric composition imposed by different manifestations of the solar activity cycle. as well as on the modelling of radiative transfer through the atmosphere and the ocean under variable environmental conditions. Overviews on the ozone issue. its monitoring and variability were extensively discussed with emphasis on the observed acceleration of ozone decline in the early 90's. This acceleration had as a consequence, significant increases in UV-B radiation observed at a few world-wide distributed stations.