The Sone tidal flat in Kitakyushu city has a dry flat of about 517ha during ebb tides. It is one of the nicest spots for the wild bird observation through the four seasons. It is also famous as the breeding ground of Horseshoe crab (Tachypleus tridentatus). A construction of an artificial island for a new airport about 3km offshore started in 1994, which was opened in March, 2006. A fishing port is under construction in the center of the Sone tidal flat. Therefore, there is a possibility that natural environments of the tidal flat may change. The aim of this study is to understand characteristics of the natural environments of the Sone tidal flat through field investigations of ground elevation, water quality, bottom sediment, and benthos. These investigation results are compared with the past findings. The results of the study indicate that the natural environments of the Sone tidal flat and its neighbor have not significantly changed at the present time. However, there is concern that a slight deterioration of bottom sediments and diversity of benthos has been detected. Detailed regular monitoring studys will be necessary.
