“Coral reefs” are the underwater calcareous reefs in the shallow marine water with sunlight penetration. Those reefs are formed by growth of various species of corals. Besides, several calcareous organisms also help an accumulation of calcium carbonate within coral reefs such as calcareous algae, shells etc., and reef formation can also be derived from the accumulation of those dead fragments. Complex structure of coral reefs is resulted from the composition of many coral species with their different structures. Within the complex structure, there are many cavities or nooks, which are appropriate habitats for several organisms such as fish, shrimps, mollusks, sea stars, sea cucumbers, sponges, soft corals, sea fans, worms and algae etc., leading this place to be the highest biodiversity in marine environment and to be more directly and indirectly utilized. Hence, various aquatic resources are caught and recreation and tourism are becoming more popular in coral reefs.
Figure Coral reefs