Primary productivity in the sea accounts for ~30% of the total global annual production. Holistic understanding of the factors determining marine productivity requires detailed knowl edge of algal physiology and of hydrodynamics. Traditionally studies of aquatic primary productivity have heen conducted hy workers in two major schools: experimental laboratory biology, and empirical field ecology. Here an attempt was made .to hring together people from both schools to share information and con cepts; each author was charged with reviewing his field of exoer tise. The scope of the Symposium is broad, which we feel is its strength. We gratefully acknowledge financial support from the Depart ment of Energy, the United States Environmental Protection Agency, the National Oceanic and Atmospheric Administration, including the NMFS Northeast Fisheries Center and the MESA New York Bight Project. Thanks are due to Mrs. Margaret Dienes, with out whose editorial skills this volume could not have been pro duced, and to Mrs. Helen Kondratuk as Symposium Coordinator. Finally, we wish to record our indebtedness to Dr. Alexander Hollaender for his tireless efforts and valuable advice in sup porting all aspects of this Symposium.