One: The Daily Growth Cycle.- The Keynote Lectures.- Diel periodicity in phytoplankton productivity.- The daily pattern of nitrogen uptake by phytoplankton in dynamic mixed layer environments.- Two: Daily Patterns of Growth in Culture and Lake.- Experimental Work.- Influence of medium frequency light/dark cycles of equal duration on the photosynthesis and respiration of Chlorella pyrenoidosa.- An algal cyclostat with computer-controlled dynamic light regime.- The effect of dynamic light regimes on Chlorella: I. Pigments and cross sections.- The effect of dynamic light regimes on Chlorella: II. Minimum quantum requirement and photo-synthesis-irradiance parameters.- Flow cytometry: instrumentation and application in phytoplankton research.- Characterization of the light field in laboratory scale enclosures of eutrophic lake water (Lake Loosdrecht, The Netherlands).- Influence of the mixing regime on algal photo synthetic performance in laboratory scale enclosures.- Diel changes in dark respiration in a plankton community.- Picoplankton photosynthesis and diurnal variations in photosynthesis-irradiance relationship in a eutrophic and meso-oligotrophic lake.- Three: Cell Cycle and Productivity.- Papers contributed to Posters.- Variations in biochemical parameters of Heterocapsa sp. and Olisthodiscus luteus grown in 12:12 light:dark cycles: I. Cell cycle and nucleic acid composition.- Variations in biochemical parameters of Heterocapsa sp. and Olisthodiscus luteus grown in 12:12 light:dark cycles: II. Changes in pigment composition.- Effect of Si-status on diel variation of intracellular free amino acids in Thalassiosira weissflogii under low-light intensity.- The `true' growth efficiency of phytoplankton as influenced by light attenuation and insolation: implications of the photosynthesis-irradiance relationship.- Nutrients versus physical factors in determining the primary productivity of waters with high inorganic turbidity.- Deep chlorophyll a maxima in the Red Sea observed by in-vivo flash fluorometry.- Dynamic versus static models for photosynthesis.- Interspecific variation in pigmentation: implications for production estimates for shallow eutrophic lakes using an incubator.