How do coral polyps build reefs?

Coral polyps build reefs by secreting calcium carbonate to form protective skeletons. These skeletons accumulate over time, creating the solid framework of a reef. Living polyps sit on top of these structures, extending their tentacles to capture food. Reefs grow through the combined activity of millions of polyps and thrive in warm, shallow waters where sunlight supports the algae that live symbiotically within the polyps. Coral reefs provide critical habitats for diverse marine life.