Individual Coral Reefs are formed by a wide variety of marine animals and plants. Coral forms by the slow accumulation and deposition of calcium carbonate (limestone) extracted from seawater.
The reef’s underlying framework is formed by stony corals and coralline red algae growing amidst the coral formations. The hard corals and coralline algae extract the materials from the seawater (shallow waters are rich in calcium and bicarbonate ions) and they combine them to form calcium carbonate or limestone.
Coral polyps use this to produce outer protective skeletons. With the passage of time their limestone skeletons form the coral reefs, which are built over decades and centuries.
Sponges and soft corals and other invertebrates assist the process as the corals grow and expand. Reefs can be atolls, barriers or fringing.
Most coral reefs are built from stony corals, consisting of polyps that cluster in groups. Polyps belong to the group which includes sea anemones and jellyfish. The corals secrete hard carbonate exoskeletons to support the coral polyps.
aussiereefbeauty 