Corals / Cho'cho'

All corals are protected species: it is illegal to collect living or dead corals.

Staghorn coral / Acropora aspera

A massive coral / Porites lutea

A soft coral / Sarcophyton sp.
Images from Coral Reefs CD

Coelenterata which also includes jellyfishes and hydrozoans. Animals in this group have stinging cells called nematocysts. When a nematocyst is stimulated, a spiny springlike structure everts and injects a venom. Fire corals are hydrozoans that produce a hard stony skeleton. They are the only corals capable of inflicting a painful sting.

Cho'cho' consist of one or more animals called polyps. Each polyp is hollow and has a centrally-located mouth surrounded by tentacles. The tentacles contain batteries of nematocysts used for defense and feeding on plankton. Instead of having an internal skeleton for support like we have, a coral polyp builds an external skeleton around itself out of a substance called calcium carbonate which is basically the same thing as chalk, marble or limestone. Cho'cho' polyps slowly accumulate small amounts of the calcium carbonate that are dissolved in seawater.

There are several basic kinds of cho'cho'. The stony corals have polyps with multiples of six tentacles consisting of an outer layer of living polyps with an internal skeleton of calcium-carbonate attached at the base to a hard surface. There are nearly 300 kinds in Guam's waters. Octocorals include the soft corals and gorgonians, commonly called sea fans and have polyps with multiples of eight tentacles. There are several major groups of octocorals with dozens of local species. The leather corals are soft corals with a flexible leathery skeleton containing numerous embedded spicules; the gorgonians have a hard but flexible skeleton of black fibrous material.

Most stony corals and some octocorals require sunlight. Corals are animals, but the kinds that build reefs have living plants incorporated into their tissues. These plants, simple, single-celled algae called zooxanthellae, live in partnership with the corals. The zooxanthellae, like all plants, use the sun's energy to produce sugars by the process of photosynthesis. These sugars provide much of the coral's nutritional needs. In turn, the coral's waste products, primarily carbon dioxide and nitrogen compounds, are used by the zooxanthellae.

Guam has two types of coral reefs. The most common is the fringing reef which extends out from the shore as a shallow platform. The other is called a barrier reef which extends up from the sea bottom at some distance away from the island and is separated from shore by deep water. The reef outside of Apra Harbor near Cabras Island, and the reef surrounding Cocos Lagoon are barrier reefs. Coral reefs are very important to our island because they serve as habitat for the fish we eat and protect us from the pounding surf when a big storm hits. Siltation and pollution have destroyed many of our reefs and it will take hundreds of years before they can recover. It is illegal to take or destroy coral. Violators are subject to arrest, fines and/or imprisonment.

There are many individual factsheets about different corals on our CD-ROM, Coral Reefs of the Mariana Islands and we also have a video, Coral Reefs: Their Health, Our Wealth.