Horizontal Distribution of Peridinium spp. (Dinophyceae) Cysts in Surface Sediments from Sameura Dam and Tomisato Dam Reservoir in Winter

Abstract

The horizontal distributions of Peridinium spp. cysts in surface sediments from the Sameura Dam and Tomisato Dam reservoirs in winter were determined to understand the mechanism of cyst deposition in this study. The cyst density downstream of the Seto River, which is an influent river of the Sameura Dam reservoir, was higher than those in the other sites (ex., Dam site). This higher cyst density downstream was probably caused by the extensive formation of cysts by motile cells and by sedimentation in the Seto River, determined on the basis of the dynamic pattern of Peridinium bipes and turbidity. In the Tomisato Dam reservoir, the cyst density of the reservoir intake formed at a low water level was higher than those in the other sites, which was considered to be caused by the deposition of cysts flowing that flowed down from upstream.