The reef community
Through geological time, different types of animals have built and lived on reefs. Throughout, the structure of the reef community has remained more or less the same.
The creatures which live as part of the reef can be divided into three groups, which interact to form the reef community.
- Reef builders form a framework of hard skeletons, the foundations of the reef. Most modern reefs are built by corals and algae, but sponges, bryozoans and bivalves have all formed reefs in the geological past.
- Reef dwellers live in the sheltered environment created by the reef builders. They do not directly build the reef framework, but their hard skeletons or shells can become part of the reef after they die. Modern reef dwellers include fish, crabs, octopus, gastropods and echinoderms, such as crinoids. Trilobites and brachiopods were common on some fossil reefs.
- Reef destroyers are animals such as starfish, sea urchins and gastropods which feed on reef building organisms. These animals are also reef dwellers. They have grinding jaws which can cut or scrape away at the calcium carbonate reef framework. This is an essential part of reef activity as these animals are food for other reef dwellers, and their activity helps to clear space on the reef and stimulate new growth of the reef builders.
Together these groups interact to make up the reef community.