Dynamics of C2 toxin and chlorophyll-a formation in the dinoflagellate Alexandrium tamarense during large scale cultivation

The production of paralytic shellfish toxins (PSTs) by the dinoflagellate A lexandrium tamarense ATCI01, a toxigenic strain isolated from South China c oastal waters, was studied in batch cultures in relatively large volumes (2 01). Under nutrient-replete conditions, this strain produced C2 toxin (C2T) as a predominant PST. In a 15-day production culture, phosphate was deplet ed by day 4, the stationary phase began at day 6, and the toxin productivit y peaked at day 10, in which the cell content of C2T reached 76 fmol per ce ll. Much of the toxin was produced after the depletion of phosphate in the medium suggesting that C2T is a secondary metabolite. Aeration with small b ubbles was useful in increasing cell mass and toxin yield. Chlorophyll-a (C h1-a) was formed in algal cells until the culture entered the stationary ph ase, after which Chl-a began to disappear rapidly from the culture while th e C2T content continued to rise. These results suggest a metabolic relation ship between Chl-a and C2T. (C) 2001 Elsevier Science Ltd. All rights reser ved.