Page 3 - The British Big Four

Coral Reefs and How They Form

C oral reefs are underwater structures made from calcium car- shallow, clear, sunny and agitated waters. Often called “rainforests
bonate secreted by corals. They are colonies of tiny animals of the sea”, coral reefs form some of the most diverse ecosystems
found in marine waters that contain few nutrients. Most coral reefs on Earth. They occupy less than 0.1% of the world’s ocean surface,
are built from stony corals, which in turn consist of polyps that about half the area of France, yet they provide a home for 25% of
cluster in groups. The polyps belong to a group of animals known all marine species. Coral reefs flourish even though they are sur-
as Cnidaria, which also includes sea anemones and jellyfish. Unlike rounded by ocean waters that provide few nutrients. They are
sea anemones, coral polyps secrete hard carbonate exoskeletons most commonly found at shallow depths in tropical waters.
which support and protect their bodies. Reefs grow best in warm,