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Coral reefs are underwater ecosystems often called the "rainforests of the sea" due to their immense biodiversity. They built by colonies of animals coral polyps, secrete carbonate to form a hard skeleton. vibrant thrive warm, clear, ocean waters and support a variety of marine life. Reefs protect coastlines from storms and erosion and provide a source of food and income for millions of people. Despite their importance, these delicate ecosystems face numerous threats from pollution and environmental changes.