Rendements et caractéristiques biologiques de cultures à dialyse continues de Phaeodactylum tricornutum opérant à divers taux de dilution

Abstract

Continous dialysis cultures of the marine diatom P. tricornutum, conducted under saturating light and using natural estuarine water as nutrient substrate, were grown at dilution rates varying between 0.30 and 0.82 d −1. Results indicate that productivity varies iversely with dilution rate. Less rapid dilution, while maintaining denser cultures, affects the two principal factors determining productivity: nutrient mass transfer and nutrient conversion efficiency of the algae. Dense cultures increase nutrient diffusion across the dialysis membrane, hence the substrate utilization efficiency of the technique. Such cultures are characterized both by a higher nitrogen conversion coefficient ( Yn) and a lower maintenance coefficient ( Ye) for this nutrient. On the other hand, slower dilution of dialysis cultures decreases nutrient availability per cell. Biochemical composition is in turn altered as dry weight, carbon and nitrogen, on a unit cell basis, are impoverished at lower dilution rates. However, chlorophyll a concentrations are not similarly affected by varying rates of dilution.