Sorption du cadmium par une population de la diatomée Phaeodactylum tricornutum en culture

The uptake of cadmium by the marine diatom Phaeodactylum tricornutum (Bohlin) maintained in batch culture was measured as a function of successive growth stages of the diatom, and of the chemical form of cadmium in the culture medium (10 g Cd.l^-1). The relative importance of adsorption and absorption of cadmium by the diatom was evaluated. When cadmium was chelated by ethylenediaminetetraacetate (EDTA) the uptake was negligible. In the absence of a chelating agent the uptake varied with the growth phase of the culture, and the major part of the uptake was by adsorption. Two opposite phenomena seen to be responsible for the processes observed: adsorption of cadmium on the cell walls followed by a gradual elution (desorption) by external metabolites.