Estimation of Transport and Origin of Suspended Particles Accumulated in the Isahaya Bay Using Diatom Tracer Method

Abstract

We used the diatom tracer method to survey the area around the Isahaya Bay to evaluate the influence of suspended particles discharged from the Isahaya reservoir. This method allowed the frustules of Skeletonema subsalsum and S. costatum, the predominant diatoms in the Isahaya reservoir and the bay, respectively, to remain even after the decomposition of cells of these phytoplanktons. We found that the greatest amounts of the suspended particles transferred within the area 1.5 km from the gates of the reservoir, at the head of the bay. We also found that most particulate organic matter in the bottom sediment originated from the primary production areas at the center and mouth of the bay. Moreover, we confirmed the reliability of the diatom tracer method from the finding that the distribution of the frustules of the diatoms in the sediment showed good agreement with that in the water column of the bay.