Chaetoceros sp. was kept in 10 1 semicontinuous cultures, compatible with pilot-scale commercial production, with 50% daily dilutions. Lighting was continuous, with cool white, or blue-green fluorescent lamps, alone or with 6.5 µmol m^-2s^-1 of white light. For each type of light, cultures were stabilized at different photonfluence rates and sled three to five times for biomass analysis. Cell yields increased with photon fluence rates, up to 432-498 µmol m^-2s^-1 for white and between 498-565 µmol m^-2s^-1 for both types of blue-green light. Above these fluxes, yields were light-saturated or even photoinhibited. For equal photon fluence rates cell concentrations were higher in white light, but biomass yields better in mixed blue-green. Chlorophylls a and c decreased with increasing light, while carotenoids showed an opposite trend. Carbon sinks were not different at low photon fluence ratesof white and blue-green light, but the mixture of blue-green light and white favoured lipogenesis over glycogenesis. At high photon fluence rates of blue-greenlight, proteogenesis increased dramatically at the expense of lipogenesis and glycogenesis in pure and mixed blue-green light respectively.