A numerical simulation of physical environments in the Ariake Sea including the effects of the tidal flat

The Ariake Sea surrounded by Nagasaki, Kumamoto, Saga and Fukuoka prefecture, Japan has a huge tidal flat area and very high productivity. However, human activities such as reclamation of this tidal flat and loading from the rivers have polluted its environments. As a result, the number of red tides and amount of oxygen deficient water in the Ariake Sea and the area where those phenomena occur has increased from 1980s. The red tide by Khizosolenia imbricata that occurred November, 2000 caused particularly severe damage to the laver cultivation. The real cause for these phenomena has not clearly been identified, But resolution of these problems requires a physical and biochemical study of the environments. As the first step in such an approach, the authors developed a method to reproduce the physical environments with high accuracy by using numerical simulation which considers the effects on tidal flat and compares them with the observed physical environments. The simulation shows good agreement with the observations made in the Ariake Sea itself.