RELATIONSHIPS BETWEEN PHOTOPIGMENTS, CELL CARBON, CELL NITROGEN AND GROWTH-RATE FOR A MARINE NANOFLAGELLATE

Ammonium-limited batch cultures of Isochrysis galbana were grown in both continuous light and 12-h light-dark cycles. The maximum observed specific growth rate (measured in terms of cell numbers) was similar under both illumination regimes, but the mean cell content of Chl a was higher in intermittent illumination. The N : C ratio of the culture was linearly related to relative specific growth rate. A highly correlated linear relationship was found between carotenoid and C, with a similar slope for both light regimes. In contrast, Chl a was linearly correlated with N, but the slope of the relationship changed with illumination and the coefficients of variation were higher. The Chl a:C ratio depended on nutritional state and on the illumination regime.