What is calcareous skeletons of certain coelenterates?

Calcareous skeletons in certain coelenterates, such as corals, are composed primarily of calcium carbonate. These structures provide support and protection for the organisms, helping them maintain their shape and structure in marine environments. The skeletons can form large reef systems, which serve as crucial habitats for various marine species. The process of skeleton formation is often linked to the organism's biological activity and environmental factors.