The behaviour of sunlight in water, and the role which light plays in controlling the productivity, and influencing the biological composition, of aquatic ecosystems have been important areas of scientific study for more than a century, and it was to meet the perceived need for a text bringing together the physical and biological aspects of the subject, that Light and photosynthesis in aquatic ecosystems was written. The book was well received, and is in use not only by research workers but also in university courses. In the eleven years since the first edition, interest in the topic has become, if anything, even greater than it was was before. This may be partly attributed to concern about global warming, and the realization that to understand the important role the ocean plays in the global carbon cycle, we need to improve both our understanding and our quantitative assessment of marine primary production. An additional, but related, reason is the great interest that has been aroused in the feasibility of remote sensing of oceanic primary productivity from space. The potentialities were just becoming apparent with the early CZCS pictures when the first edition was written. The continuing stream of further CZCS studies in the ensuing years, enormously enlarging our understanding of oceanic phytoplankton distribution, and the announced intention by space agencies around the world to put new and improved ocean scanners into space, have made this a particularly active and exciting field within oceanography.