Most of them are colonial, and all secrete a hard skeleton made of calcium carbonate. The animals themselves, called polyps , form the outer living layer of the coral skeleton. The characteristic color of living coral is due to the presence of algae, called zooxanthellae , which live inside the coral polyp. The coral and algae have a symbiotic relationship in which each benefits from the other. Most stony corals produce colonial forms that are attached to the substrate, but a few are solitary and unattached.
Coral reefs are an important resource for Hawaii.
Corals and coral reefs provide food and habitat for many fish and invertebrates. Most stony corals grow very slowly, so damaged reefs may take hundreds of years to recover. Please help us to protect our coral resources. Contact Diane Nakashima . Web page design by Ben Cheng .