We examined the effects of nutrient discharge from land areas to nori farms around the Kako River estuary, eastern part of Seto Inland Sea, off Hyogo Prefecture. Horizontal distribution of high DIN concentration water at the surface was frequently observed along the east coast of the Kako River estuary, off the Befunishi area in Higashiharima Port. The water with high DIN concentration originated from the port with industrial and sewage treatment plant effluents, and the river. These results suggest that nutrient discharge from the river and port influenced nori production in the coastal farms in the eastern Kako River estuary.