The production of Nori (Pyropia yezoensis) in the Seto Inland Sea is getting lower because of the bleaching of Nori which is caused by nutrient deficiency. In this study, we examined effects of nutrient discharge on Nori aquaculture area in Kako River estuary. In the aquaculture area, nutrient discharge from the river, sewage treatment plant and industrial effluent sustained the Nori production in the winter season. A numerical simulation estimated the behavior of the riverine water and revealed the effects of nutrient discharge on the nutrient environment of the aquaculture area. We also evaluated the effects of moderate operation of the sewage treatment plant on the nutrient environments. We demonstrated the increase of nutrient flux in the aquaculture area and figured out the effective area of the moderate operation.
