Abstract
Trend of eutrophication and magnitude of marine-derived organic matter contributing to organic pollution were investigated in the Osaka Bay, Seto Inland Sea, which is semi-closed coastal bay surrounded by highly developed industrial areas and has been subjected to the effect of human activities. Average standing stocks of total nitrogen and total phosphorus in the bay during the 1990's were estimated to be 11,930ton and 1,620ton, respectively. These values decreased by 22% and 13% of those during the 1980's, respectively. The eutrophic level during the 1990's was approximately same as that during the mid 1970's. Results from carbon stable isotope ratio (δ13C) indicate that more than 80% of particulate organic carbon standing stock came from marine-derived organic matter in the Osaka Bay. This value was at least over 30% high compared to that estimated by the relation between particulate organic carbon and pigment.
