Intrusion of External Saline Water Influencing Anoxic Water in Uranouchi Bay.

In Uranouchi Bay, the external water density becomes higher than that of internal water in the summer stratification season, and the external saline water intrudes into the bottom of the bay at the spring tide. Much heat and oxygen is also transported into the bottom layer along with the water intrusion. Although the strong anoxic water is formed from the beginning of June in the bottom of Uranouchi bay, anoxic water masses on the bottom disappeared for a while after the intrusion, and the bottom water temperature suddenly rose about 2 to 3°C in a few days, but anoxic water was formed again at the next neap tide due to the high DO consumption and the upwelling of bottom anoxic water. These conditions killed a large number of cultured yellowtail fish, as occurred at the beginning of September 1988.