Coral reefs are primarily made of calcium carbonate, which is secreted by coral polyps as they build their skeletal structures. These reefs are formed over thousands of years as polyps form colonies, creating complex and diverse habitats critical to marine ecosystems. This structure not only supports a wide array of marine life but also protects coastlines from erosion. The health of coral reefs is essential for biodiversity, fishing industries, and tourism, making their conservation increasingly vital in the face of climate change and ocean acidification.