The experimental period was 20 d. For each day and each
marine diatom species, a flask (250 ml) containing 10 ml of
inoculum and 140 ml of culture medium was prepared (Fig.
1). After every 24 h of incubation, one of the flasks was taken
and the determination of cell density (growth) curve, nutrient
concentrations and extracellular carbohydrate concentrations
was done. Nutrient concentrations and extracellular carbohydrate
concentrations were determined on the filtrate obtained
after filtration of the culture by 47 mm pre-combusted Whatman
GF/C filters. Samples for the characterisation of the
exopolysaccharides were obtained from the filtrates corresponding
to the final period of incubation (17–20 d). All the
chemical analyses described below were carried out in triplicates