COMPARATIVE PHYSIOLOGICAL STUDY OF MARINE DIATOMS AND DINOFLAGELLATES IN RELATION TO IRRADIANCE AND CELL-SIZE .1. GROWTH UNDER CONTINUOUS LIGHT

Cell division rates and chlorophyll a and protein contents for ten diatom and dinoflagellate species were measured. Species were chosen to include a wide range of cell size in terms of both cell volume and cell protein: from 0.004 ng protein/cell for a small Chaetoceros sp. to 2.2 ng protein/cell for Prorocentrum micans Ehrenberg. Experiments were conducted in batch or semi‐continuous cultures at 21 C under continuous illumination from 8–256 μEin .m‐2'.s‐1. Light saturation of cell division occurred at 32–80 μEin m‐1 s‐1 for all species, with no observable difference between the two phylogenetic groups. When the light‐saturated cell division rates were plotted against cell size as protein/cell, the diatoms and dinoflagellates fell on two separate lines with the diatoms having higher rates. Chl a /protein ratios (μg/μg) decreased with increasing irradiance. The diatoms had higher chl a per unit protein. The relationship between cell division rate and the chl a/protein ratio is discussed. Copyright © 1978, Wiley Blackwell. All rights reserved