2018 Volume 82 Issue 1 Pages 26-35
Dynamics of dissolved inorganic nitrogen (DIN) in relation to the color of fresh nori (Pyropia) were examined around nori farms in the coastal waters of the northeastern part of Harima Nada (off the coast of Akashi City and Harima Town in Hyogo Prefecture). DIN concentration in surface water was higher inside the ports due to industrial effluent and rivers, and around the outfall of treated sewage effluent. Horizontal distribution of high DIN concentration in surface water extended in the east-west direction along the coastline. On the other hand, offshore concentrations were lower. The dynamics of salinity and NH4–N concentration suggest that during the ebb tide (eastward flow in this area), discharge from ports and treated sewage effluent in the western area can influence the coastal nori farms east of this study area. Also, the numerical simulation method results showed that DIN supplied from the treated sewage effluent flowed eastward during the ebb tide, and reached the coastal nori farms. The quality of fresh nori produced in the eastward coastal nori farms from this study area was better than that from the offshore area, presumably influenced by the nutrients discharged from the ports and the treated sewage effluent.
