How do coral polyps build the Great Barrier Reef?

Coral polyps, which are tiny marine invertebrates, build the Great Barrier Reef by secreting calcium carbonate skeletons. These polyps are similar to sea anemones and often live in colonies, with each polyp contributing to a shared, rigid calcareous skeleton. Over time, these skeletons accumulate, forming the massive limestone structure of the reef.12

Reef-building corals, particularly stony corals, thrive in shallow, sunlit tropical waters with specific temperature and salinity requirements. The symbiotic algae (zooxanthellae) living within the coral tissues play a crucial role by aiding in the secretion of calcium carbonate. Coralline algae and bryozoans also contribute by cementing these skeletal remains together, further solidifying the reef structure.132