　Recently, coral reefs in Yaeyama are degrading and losing its functions.
The potential causes are:

Crown of Thorns Starfish

・Crown of Thorns Starfish is a large size starfish which diameter sometimes reaches up to 50cm. The starfish is covered with numerous poisonous spines.

・The outbreak of this starfish occurred in 1980s in Yaeyama causing mass predation of corals that destroyed vast coral reef area.

・ There are numerous other kinds of organisms that predate on corals. However, we should note that these organisms are not our enemies but are important components of reef ecosystems.

・The population of this starfish is in increasing trend recently.

Bleaching event

・Coral bleaching occurs in inappropriate environmental conditions such as high/low seawater temperature, high/low UV radiation, etc.

・The picture at the left shows an example of coral bleaching that occurred when sunlight has been blocked. It is said that corals are sensitive organisms.

　Coral bleaching occurs at several stages when the surrounding environment changes unfavorable for corals to live. Such an aberration will trigger the symbiotic algae to leave the host corals. When certain amount of algae has been lost from the coral tissue, white coral skeleton underneath the tissue could be seen-through. When such a stage continues, corals can no longer survive and will eventually die out.

Red soil run offs

・When heavy rain falls in the terrestrial area near the coast, red murky water runs off into the coastal ocean from the bare ground of construction fields and/or farmlands. Then the adjacent reefs will be covered with the fine particles of red soil in the murky water and sessile corals will end up smothering (or be suffocated by the particles).

・This red soil run off causes nothing but problems not only reduce fish catches but also in tourism and agriculture.

Unplanned development

・When the closely linked relationship of mountains, rivers and ocean were broken off by unplanned coastal development, it will further adversely affect coral reefs.

・Therefore coral reefs are highly dependent on healthy linkage of forests, rivers, mangroves and tidal flats.

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