2011 年 75 巻 3 号 p. 143-153
In summer 2010, a harmful bloom of the raphidophycean flagellate Chattonella antiqua occurred in the Yatsushiro Sea. The short-term dynamics of the C. antiqua bloom and oceanographic conditions were investigated by intensive field observations. The bloom first appeared in the west-central area of the Yatsushiro Sea at the end of June. It then expanded rapidly to include the entire area in early July, and high cell density with short-term fluctuations continued to exist till the end of July. In the southern area, increase in the cell density of C. antiqua was synchronized with the timing of low salinity water covering the surface layer, which originated in the fresh water discharge from the Kuma River in the northern area of the Yatsushiro Sea. This synchronization implies that the dense water containing C. antiqua was transported by a density-driven current from the north-central area, and/or cell density was enhanced by the stratification associated with the low salinity riverine water. A rapid increase in cell density in the surface layers and the subsequent deepening of dense water below 20 m occurred in the southern area in late July, resulting in enormous damage to cultured finfish.
