渦鞭毛藻Peridinium bipesのシスト形成に関する実験的研究

抄録

The dominant factors of encystment in a wild strain of Peridinium bipes (Dinophyceae) were studied through encystment experiments in culture medium using natural water. The wild strain of P. biopes and the natural water sample were collected from Gogawa Reservoir in Wakayama Prefecture. Based on the results of the encystment experiments, the optimal temperature for encystment was found to be in the range of 10 to 15°C, and no encystment was observed at 25°C. In addition, natural water during the water bloom of P. bipes induced encystment of vegetative cells. Nutrients concentrations of the natural water were very low, 0.025 mgN·l^-1 of nitrate ion and 0.003 mgP·l^-1 of orthophosphate ion, because of the uptake by phytoplanktons. Accordingly, it was inferred that resting cysts of P. bipes are formed during the bloom and that the new cysts serve as a seed population for the next bloom. Therefore, it is strongly required to develop countermeasures to break the daisy chain of bloom and encystment.