Coral reef
Coral reefs are biogenic marine structures built primarily by reef‑building stony corals that secrete calcium carbonate skeletons in warm, shallow seas, where they create highly diverse habitats supporting thousands of species. Although they cover less than 1% of the ocean floor (about 0.2% of the seafloor), they underpin fisheries, coastal protection, and tourism for hundreds of millions of people across more than 100 countries and territories. Reefs are increasingly threatened by ocean warming, mass bleaching, ocean acidification, disease, pollution, and overfishing, prompting global monitoring, conservation, and restoration efforts.
