Effects of B group vitamins on the growth of toxic dinoflagellate Alexandrium catenella

Abstract

Physiological growth characteristics of Alexandrium catenella (Whedon et Kofoid) Balech, toxic dinoflagellate, were examined in axenic, batch cultures with specific reference to B group vitamin requirements. A. catenella required essentially vitamin B12 among the B group vitamins for their growth. It was found that growth rates and final cell yields were dependent on the vitamin B12 concentrations in the media. Under the conditions of our batch culture experiments, the half-saturation constant for growth of vitamin B12 (Kμ) and maximum growth rate (μ′m) were 0.22 ng/L and 0.55 day-1, respectively. The minimum cell quota of vitamin B12 was estimated at 0.65 fg/cell or 27 molecules/μm3 of the cell volume. In this experiment, A. catenella could grow at almost a maximum growth rate at high vitamin B12 levels of eutrophied coastal waters. The comparison Kμ and μ′m between A. catenella and other red-tide species suggests that this organism can win competition with some red-tide species under low B12 concentrations.