Abstract
This study documents the inhibition effect of an oyster reef developed on a tidal flat in Ariake Sea on the formation of hypoxia that occurs every summer and greatly damages fisheries. An ecosystem model including material fluxes associated with the oyster reef was newly developed and was validated through a comparison with the observed dissolved oxygen concentration. The oyster reef decreased the concentration of phytoplankton and particulate organic matter through its food consumption with a high filtration rate and increased the dissolved oxygen concentration not only in the area close to it but also in a wider area far from the reef. Numerical experiments with/without the oyster reef indicate that the hypoxia was decreased in its volume by about 40% at most by the oyster reef. In the case in which another oyster reef was developed virtually in a numerical simulation, the degree of hypoxia was further reduced. However, it would be difficult to eradicate hypoxia only by the artificial construction of an oyster reef. Therefore, for further restoration of the estuarine environment, the combination of oyster reef development and other effective environmental measures is necessary.
