Interest in oceanography and marine biology and its relevance to global environmental issues continues to increase, creating a demand for authoritative reviews that summarize recent research. Oceanography and Marine Biology: An Annual Review has catered to this demand since its foundation, by the late Harold Barnes, more than 40 years ago. It is an annual consideration of basic areas of marine research; it returns to certain topics when appropriate in future volumes and adds new topics as they arise. The favorable reception accorded to all the volumes shows that the series is fulfilling a very real need: both reviews and sales have been gratifying. The 41st volume follows closely the objectives and style of the earlier volumes, continuing to regard the marine sciences-in all their various aspects-as a unit. This edition adds commentary on exotic mollusks in the Mediterranean, the diet of harbor porpoises and other topics. Experts treat the physical, chemical and biological aspects of marine science. The series is an essential reference text for researchers and students in all fields of marine science and related subjects, and it finds a place in the libraries of marine stations and institutes as well as universities. It consistently ranks among the highest in the marine biology category of the citation indices compiled by the Institute for Scientific Information.