Abstract
We summarized the findings about spatial and temporal variations in Chattonella blooms in Yatsushiro Sea based on previous studies using a numerical model and monitoring data. Chattonella bloom（＞1，000cells ml－1）initially formed in the northern area in late July 2009, and subsequently expanded rapidly to the southern area. The model results indicated that southward evolution of the bloom was primarily controlled by the passive transport imposed by fresh water discharge from Kuma River and a northeasterly wind. The appearance of the riverine water in the southern area can be explained by the balance between the wind stress term and pressure gradient term between the northern and southern areas. Both terms can be estimated from in situ data such as sea surface density, depth of the halocline, wind speed and direction. The findings will enable nowcasting of bloom expansion when a bloom develops in the northern area.
