The effect of water temperature and light intensity on the growth rate and the toxicity of Protogonyaulax tamarensis was examined using a monoclonal culture isolated from Ofunato Bay, Japan in March, 1984. The growth rate decreased with the decrease of either light intensity or temperature. The amount of toxin produced increased concomitantly with the decrease of the growth rate. However, the increase of the toxicity under low growth rate was less remarkable when the growth rate was lowered by the decrease of light intensity. This indicates that photosynthesis plays an important role in the production of toxin in P. tamarensis.
Materials and methods
Isolation and culture of the Protogonyaulax tamarensis clone
A single vegetative cell of Protogonvaulax tamarensis was isolated from Ofunato Bay, Iwate Prefecture, Japan in March, 1984, when this species was blooming. This clone (OF84423D-3) was mass cultured and maintained in enriched seawater T1 medium (Table 1) at 15 ~ under an illumination of 3 000 lux with a 16 h light:8 h dark cycle, using cool-white fluorescent lamps. Culture experiments with different light intensities and water temperatures were carried out after acclimation of the clonal population to respective experimental conditions during a period of 20 d.