The marine microalga Chlorella autotrophica was cultured semicontinuously under light-dark synchronizing conditions at two nutrient concentrations (2 and 4 mmol N.L-1) and five rates of daily renewal (from 10 to 50% of culture volume). Under such conditions, the biochemical composition of C. autotrophica was strongly influenced by the renewal rate, but unlike other marine microalgae, the nutrient concentration had no effect on the biochemical composition of the organic fraction of the microalga at a given growth rate. Results suggest that this species exerts a strong control over metabolic pathways, independent of the nutrient concentration in the medium.