What we can learn from Eutrophication and occurrences of harmful algal blooms in the Seto Inland Sea, Japan. Reduce urea nutrient pollution
The Seto Inland Sea is the largest enclosed coastal sea in Japan and is also a major fishing ground includ- ing aquacultures of fish, bivalves and seaweeds. The incidents of red tides dramatically increased in frequency and scale in the Seto Inland Sea along with serious eutrophication in the 1960s and 1970s. The maximum incident of 299 was recorded in 1976, but the incident has since shown a clear decreasing trend, reaching about 100 per year in the late 1980s by virtue of regulation by law, and this level has been maintained thereafter with the level of nutrients supporting red tide occurrences. The “Law Concerning Special Measures for Conservation of the Environment of the Seto Inland Sea” was legislated in 1973 and industrial loading was decreased to half the level of 1972.
In the 1960s, the coastal region of the Seto Inland Sea played a leading role in contributing to the explosive eco- nomic growth of Japan, resulting in extremely heavy amounts of pollutants and serious eutrophication. Figure 2 shows the pollutant loads of COD (Chemical Oxygen De- mand), total phosphorus and total nitrogen in the Seto In- land Sea. In 1973, the “Law Concerning Special Measures for Conservation of the Environment of the Seto Inland Sea” was enacted, and “Total Pollutant Load Control” was established to reduce the total quantity of organic pollutants in terms of COD from factories, sewage treatment plants, etc. The enactment of this law was triggered by a red tide of Chattonella antiqua (Hada) Ono, which caused the largest economic loss by the mass mortality of cultured yellowtails (7.1 billion yen) in the summer of 1972. As a result of this law, the quantity of COD dumped in the Seto Inland Sea, which was 1700 tons per day in 1972, had been reduced to 717 tons per day by 1999 (Ministry of the Environment Government of Japan & the Association for the Environ- mental Conservation of the Seto Inland Sea 2001)
APP Advocate Precautionary Principle 
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