Mangrove forests are high productivity habitats located in estuarine regions in the tropics and subtropics. The mangrove forests on Iriomote Island can be classified as subtropical. The purpose of this study is to document the mangrove environment in inner Funaura Bay, Iriomote Island, Okinawa Prefecture. The inner part of Funaura Bay is enclosed by an embankment, and is connected to the ocean by a small channel of about 160 m width.
A survey of water quality showed that there is a strong halocline in inner Funaua Bay due to the input of freshwater from river. Phytoplankton abundance is high due to the input of nutrients from the mangrove swamp. A survey of the surface sediments in the bay showed that the tidal flats consist of sand and carbonate with low total organic carbon(TOC)and low total sulfur(TS)contents, which indicates an oxic environment. On the other hand, the sediments of the mangrove swamp consist of sand, mud, and carbonate with enriched TOC and TS contents, which indicates an oxygen poor environment.