Abstract
Physiological characteristics of the growth of two strains of Chattonella antiqua (HADA) ONO (Raphidophyceae), haarmful red tide phytoplankters, were examined in axenic clonal cultures with special reference to B group vitamin requirements.
C. antiqua Harima-77 and TSU-8011 preferred a relatively high concentration of nutrients, and required essentially vitamin B12 among the B group vitamins for their growth. It was found that their growth rates and final cell yields were dependent on the vitamin B12 concentrations in the media. The half-saturation constant of vitamin. B12 for each strain was small:0.05ng/l for Harima-77 and 0.35ng/l for TSU-8011. The amount of vitamin B12 required to maximize final cell yields was around 10ng/l for Harima-77 and 20ng/l for TSU-8011. The maximum specific growth rate of each strain was 0.69 and 0.48 day-1, respectively. The minimum cell quota of vitamin B12 was estimated at 4.7×10-4pg/cell or 11.7 molecules/μm3 of cell for Harima-77 and 1.6×10-3pg/cell or 27.5 molecules/μm3 of cell for TSU-8011.
These results suggest that vitamin B12 in seawater may be one of the principal factors con-trolling the growth of C. antiqua, and that the amount of the vitamin required to maximize both growth rates and growth yields is around 10 or 20ng/l.
