This volume provides a refereed selection of the proceedings of the 31st European Marine Biology Symposium, held in St. Petersburg, Russia, in September 1996. State-of-the-art reviews and studies on adaptational processes in marine organisms such as adaptations to fluctuations in salinity, temperature, oxygen and pollutants which are reflected in different types of ecophysiological responses and interactions of marine organisms, including predation, parasitism, intraspecific competition and epibiosys were presented at the symposium proceedings. Research from both eastern and western Europe contributed to this project and during the symposium differences in scientific approaches and views between these two groups became apparent. The contents of this volume reflect these