Growth and paralytic shellfish toxin production by the dinoflagellate Alexandrium catenella cultured under monochromatic light

Abstract

To explore how light wavelength affects the growth of a dinoflagellate species and its production of paralytic shellfish toxin (PST), we examined the growth and PST production of Alexandrium catenella (Ac) cultured under monochromatic light. The Ac strain was cultured for 21 days under blue (470 nm), green (530 nm), or red (660 nm) LED irradiation (Blue, Green, and Red groups respectively). During the culture period, the cell density (Cd) increased rapidly in Blue and slowly in Red, while the cell volume (Cv) decreased in Blue, but gradually increased in Red. In Green, Cd increased slowly, but Cv decreased. Interestingly, the increase in the cell biomass per unit medium volume was similar in Blue and Red, suggesting that the cell biomass of Ac increases equally by either an increase in the cell number under blue light, or by an increase in the cell volume under red light. HPLC analysis for PST revealed that the amount of toxin produced per cell, cellular toxin concentration, and toxin content per unit medium volume were highest in Red, followed by Green, and then Blue; i.e., Ac produced more PST under red light than blue light, despite the equivalent increase in the cell biomass under both conditions.