Coral distribution and diversity in Sakiyamawan–Amitoriwan nature conservation area of Iriomote Island in Japan

Abstract Sakiyama and Amitori bays of Iriomote Island in Japan are adjacent, but their coral distributions differ considerably. This study investigates the differences in coral distribution and diversity between both bays from a diversity index and intermediate disturbance hypothesis (IDH) views. In Amitori Bay, tabular and branching corals dominate the mouth and inner parts of the bay, respectively. Coral diversity is the maximum in the intermediate part of the bay, realizing IDH. In Sakiyama Bay, branching and massive corals dominate the reef edge and the coast sides of the bay’s intermediate part, respectively. Coral diversity is the maximum in the reef edge part of the bay, and IDH is not realized. The difference in the soil inflow and the geographical characteristics between both bays significantly influences the coral distribution and diversity between both bays.