7. Transport Properties of Soil Particles in Sakiyama and Amitori Bays

The actual states of soil particle transport in and exchange between the Sakiyama and Amitori bays, Iriomote Island, Japan, were investigated using atmosphere–ocean–river observations and numerical simulations. Results show that in both bays in summer, large particles (≥15 μm) do not move from areas near the river mouths. Small particles, however, do move to the respective east sides of the bays. In winter in both bays, large particles move to the respective centers of the bays from areas near the river mouths, whereas small particles move to the respective west sides of the bays. Furthermore, soil particles move mainly from Sakiyama Bay to Amitori Bay in summer, but this direction is reversed in winter. These features are explainable mainly by seasonal differences in wind speed and direction, but the combination of seasonal differences in wind speed and direction, the wind-driven current and the topography are also important for them. The results are useful for assessing soil particle effects on coastal oceanic ecosystems, such as those containing reef-building coral and Enhalus acoroides, and their effective conservation in natural conservation areas of the Sakiyama and Amitori bays.