Transport properties of soil particles in Sakiyamawan–Amitoriwan nature conservation area, Iriomote Island, Japan

Abstract

Abstract 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. The results show that in summer in both bays large particles (≥15 μm) do not move from the vicinity of the river mouths. Small particles, however, do move to the respective east sides of the bays. In winter in both the bays, large particles move towards the center of the bays from the vicinity of the river mouths, whereas small particles move to the respective west sides of the bays. Furthermore, soil particles move mainly from the Sakiyama to the 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 among seasonal differences in wind speed and direction, the wind-driven current and the topography is also important for them. The results are useful for assessing soil particle impact on coastal marine ecosystems, such as those containing reef-building coral and Enhalus acoroides, and their effective conservation in the natural conservation areas of the Sakiyama and Amitori bays.

Keywords

• Iriomote Island
• Sakiyamawan–Amitoriwan nature conservation area
• Sakiyama bay
• Amitori bay
• Soil particle
• Coastal marine ecosystem