Water and sediment qualities were surveyed from April, 1996 through March, 1997 in Hakata Bay for the water-quality modeling. Using the results, the seasonal variations of water qualities were discussed and the ability for water-quality purification at the tidal flat zone was estimated. The amount of organic matter removed by benthos at Wajiro tidal flat was about 2 times larger than that at the reference area. The amount of COD removed by benthos at Wajiro was the same order of magnitude as Banzu tidal flat.
