With growth rates of 0.3 to 2 centimeters per year for massive corals, and up to 10 centimeters per year for branching corals, it can take up to 10,000 years for a coral reef to form from a group of larvae. Depending on their size, barrier reefs and atolls can take from 100,000 to 30,000,000 years to fully form.
How do coral reefs reproduce?
This mass reproduction only happens once a year. It involves colonies and species of coral polyps simultaneously releasing tiny egg and sperm bundles from their gut cavity into the water. By expelling the eggs and sperm at the same time, the coral increases the likelihood that fertilisation will take place.