Mangroves are constituent trees and shrubs of tropical and subtropical intertidal forest communities. That the flooding by tidal rhythm makes the soil in which mangrove forest distributed anoxic or hypoxic, causes very severe condition in acquisition of energy for the root system. Therefore, acquisition of oxygen to synthesize ATP and anaerobic respiration is very significant. Simultaneously, It is indispensable to secure enough light energy to produce saccharide for ATP synthase. The difference of the ability to secure light energy in different mangrove species is not only the factor limited the distribution of individual seedlings, but also the main factor determining the ecological niche of individual species. The purpose of this study is to reveal how the difference of the flooding frequency and the light circumstances affect the ecological niche of major mangrove species in Iriomote Island, Okinawa, Japan.