EFFECTS OF SILT AND CLAY CONTENT IN SEDIMENTS ON A “SINKING EVENT” AT AN ARTIFICIAL TIDAL FLAT IN OKINOSU, TOKUSHIMA CITY

Abstract

 An artificial tidal flat was created to compensate for the loss of a natural tidal flat in Okinosu, Tokushima City, Japan; however, ecological conditions in the artificial habitat of benthic animals differ extensively from those in the natural habitat. In particular, the mud snail Batillaria cumingi, which dominated the natural tidal flat, was rarely found in the artificial habitat.
 We confirmed that a “sinking event” occurred in the artificial tidal flat. From the results of our study, we suggest that the “sinking event” was a result of the low silt content in the sediments of the artificial habitat. The amount of silt and clay has decreased from the bottom sediments of the artificial tidal flat. Ground density is small because the amount of clay in the bottom sediments is little. This resulted in the aggravation of “sinking rate.” In addition, more biomass was observed in a spot with higher silt and clay content than in other parts.