CHAPTER 1 INTRODUCTION 1.1 Background of study Corals are the foundation species of tropical coral reef ecosystems. They directly facilitate thousands of associated species by generating the physically complex reef structure (Bruno & Bertness, 2001). Coral reefs are the underwater ecosystems were held together by calcium carbonate structures which is secreted by corals and also are the most diverse and beautiful of all marine habitats. Often called "rainforests of the sea", this is because coral