Page 179 - Hawaii: Diving, Surfing, Pearl Harbor, Volcanoes and More

Coral Reefs and How They Form

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