Dōkai Bay

Dōkai Bay (Japanese: 洞海湾, Hepburn: Dōkai Wan), located in Kitakyushu City, Japan, is a long, narrow inland waterway-like bay measuring five to six hundred meters wide and 13 kilometers long.

In modern times, it faces heavy industrial areas and once suffered from severe pollution and water contamination, but after a long period of successful purification efforts, the water quality has improved and the ecosystem has recovered.

[1][3] The flow pattern of water masses in Dōkai Bay is a typical estuarine circulation.

[5] After that, the government strengthened its anti-pollution measures, and Japan's industrial structure changed.

[1][5] As a result, the bay has recovered to the point where it is home to more than 100 species of fish and shellfish as of the 2020s.