CHEMICAL-COMPOSITION OF THE COCCOLITHOPHORID EMILIANIA-HUXLEYI UNDER LIGHT-LIMITED STEADY-STATE GROWTH

Changes in the chemical composition of the coccolithophorid Emiliania huxleyi as a function of growth rare were examined on cells maintained in continuous cultures. The cellular content of particulate organic ( POC) and inorganic carbon (PIC) increased with growth rate. The PIC/PO C and the POC/Chlorophyll-a (Chl.-a) ratios did not show any distinct variation with growth rate. The organic composition of E. huxleyi was characterized by the presence of large amounts of lipids (45-60% of PO C) and comparatively low protein-C cell quotas (25-30% of POC). The re lative contribution of lipid-C to POC increased linearly with growth r ate whereas those of protein-C and carbohydrate-C showed an opposite t rend, The percentage of lipid-C relative to total cellular organic car bon increased as a function of total carbon cell quota. The patterns o f carbon incorporation into photosynthetic end products were consisten t with the measured biochemical composition; The rates of dissolved ca rbon release were low, representing 1-4% of the total carbon incorpora tion. The significance of these results for the understanding of E. hu xleyi bloom dynamics is discussed.