Question

what is coral reef??

Answer 1

Coral reefs are diverse underwater ecosystems held together by calcium carbonate structures secreted by corals. Coral reefs are built by colonies of tiny animals found in marine water that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups.

Answer 2

Coral reefs are underwater structures made from calcium and carbonate secreted by corals.