RELATIONSHIPS BETWEEN OCEAN CURRENT FIELDS AND CORAL HABITAT ENVIRONMENT IN AMITORI BAY, IRIOMOTE IS., JAPAN

Abstract

  In order to identify the relationships between ocean current fields and coral habitat environment in Amitori Bay, Iriomote Island, Japan, water mixing process of tidal flow and river flow are investigated by field survey and numerical analysis. The temperature, salinity, and illumination intensity are observed at several points in the bay during a 2-month period. The field survey indicates that the river water mass of lower temperature and lower salinity is likely to flow selectively into the eastern side of the bay, especially under the conditions of nocturnal low tide and calm weather. Furthermore, an idealized numerical analysis based on the coastal current model is realistically capable of representing the water exchange process between tidal flow and river flow in the bay, and reproduces the asymmetric distributions of the surface salinity as seen in the observations. The remarkable asymmetry is considered to be induced by the complex topographic effects and to affect spatial heterogeneity in the coral habitat distribution in Amitori Bay.