The Xisha Islands consist of more than 30 islands. large and small, as well as bars,reefs and shoals. With the exception of Gaojianshi (the Volcanic Rock), they are allcoral reefs. However, little is known about what biotic process has been operating inthe formation of these coral reefs. Some authors suggest that it is mainly due to theprocess of reef-building corals. Others consider that coralline algae (or calcareousalgae) have been rather important in the formation of the reefs. Similarly, disagreementexists on whether there are “algal-ridges” on the windward sea side. Some are of theopinion that there are “algal-ridges” everywhere in Xisha Islands, but others assertdefinitely that there are no “algal-ridges” in Xisha Islands. The Xisha Islands consist of more than 30 islands. Large and small, as well as bars, reefs and shoals. With the exception of Gaojianshi (the Volcanic Rock), they are allcoral reefs. However, little is known about what biotic process has been operating inthe formation of these coral reefs. Some authors suggest that it is mainly due to the process of reef-building corals. Others consider that coralline algae (or calcareousalgae) have been rather important in the formation of the reefs. Similarly, disagreementexists on whether there are “algal-ridges ” on the windward sea side. Some are of theopinion that there are “algal-ridges ” everywhere in Xisha Islands, but others assertdefinitely that there are no “algal-ridges ” in the Xisha Islands .