抄録
We investigated the geography by the echo sounder and the sediment surface with the side scanning sonar, and collected the sediment cores at three points off Kumamoto City, to environmental reconstruction of the history of oceanic conditions since the 1950's, and to evaluation of the influence of sediments on marine organism.
The sandy bank off Yokoshima has been lost the function as the habitat of marine organism, because new sediments are not deposit on the slop and bottom in the dredged holes, and the mats ofModiolus comptusare not distributes on the surface of the bank. Muddy sediments in the Kumamoto area deposited after the latter half of 1970's are thick (ca. 80cm) off Midorikawa River, and became thin toward the north (less than 1cm off Kikuchigawa River). The limit of diffusion in mud exists off Yokoshima. The rapid increase of the haul ofRuditapes philippinarumwas closely related with the expansion of the sediments mixed coarse grains such as the shell fragments, sand, and gravel. In addition, the individuals of the clams increased in the sediments with less than 60% of mud in core sample.
