4 - Coral reefs

Abstract

This chapter reviews Coral reefs. Out of several reef building organism like red algae, sponges, and molluscs, coral are by far the most important in terms of productivity. They are highly productive ecosystems in an environment which is stable but poor in nutrients. Coral reefs are predominantly formed by hermatypic scleractinian corals and hydrocorals that live in symbiosis with zooxanthellae or dinoflagellate algae. Reef can be divided into four major types: fringing reefs, barrier reefs, atolls reefs, and platform or patch reefs. The outstanding biodiversity in coral reefs is attributed to a fine tuned annidation of the single species that could take place in a quarter of million years. For local fisheries of Indonesia coral reefs belong to the most important fishing grounds, though, they are easily destroyed by nonsustainable methods of exploitation. Presently the most severe impacts on coral reefs in Indonesia are siltation caused by terrestrial runoff due to deforested hinterlands, nonsustainable methods of marine resource exploitation, namely dynamite, cyanide and big vessel fishing.