諌早湾閉切り前後における底質の元素組成の変化

Isahaya Bay was the largest intertidal mud flat in Japan．In April 1997，the bay was closed by a dyke for reclamation and was isolated from the Ahake Sea．This resulted in the formation of stagnant and deteriorated condition in the bay，especially in the inner side of the dyke．Core samples from both the inner and outer sides of the dyke confirm the abrupt changes in lithology，biota，and various geochemical parameters．Mud samples in the upper parts which were deposited after the closure show higher concentrations of Pb，Zn，Cu，P_2O_5，TOC and TN，suggesting element accumulation in sediments under reducing conditions．This enrichment may be related to the disappearance of an ecosystem which previously effected bioremediation．