数値モデルを用いた備讃瀬戸東部海域のノリ色落ちに関する研究

概要

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In fiscal year 2002, the production of nori (Porphyra sp.) markedly decreased to 60 % of the normal annual Nori yield at Kagawa prefectural coast, eastern Bisan-Seto. Moreover, the areas where the bad harvest was observed were confined to the northern part and the southwestern part of Shodo Island, and the annual Nori yield at these areas was about 30 % of that in the average year. Matsuoka et al. (2005) studied the horizontal distributions of salinity and nutrients, and they suggested that discoloration was mainly due to the small rainfall, and small nutrient load from the Yoshii River caused bad harvest in these areas. However, it was still unknown that how much influence the nutrient load from Yoshii River will have on these nori culture grounds. In the present study, inorder to investgate the origination of the nori discoloration, we calculated the trajectories of nutrient particles from the mouth of Yoshii River to the nori culture grounds using the multi-level numerical model. As the results, it was found that the trajectories of nutrient were affected by west wind velocity. It was supposed that bad nori harvest in fiscal year 2002 may due to little rain in the autumn. In addition, the nutrient supply to bad nori harvest area from the Yoshii River flowed from Okayama Prefecture was important for nori culture.
2006-10-31