Research on the Discoloration of Nori (Porphyra) and Characteristics of Water Quality Using the Numerical Model

In and around the Seto Inland Sea Japan, there are many aquaculture facilities for Nori (Porphyra). Recently, the production of Nori (Porphyra) severely decreased at Kagawa prefectural coast, eastern Bisan Seto. We have conducted the field research and calculated the trajectories of nutrient particles under the condition in which western wind velocity changes using the numerical model. From the results of field research and numerical simulation, we suggested that Nori bad harvest was caused due to a little rain in the autumn season. It was also suggested that at Nori bad harvest area, the nutrient supply by river discharge was so important for aquaculture of Nori.