Corals are animals, but they also have microscopic, single-celled plants living in their tissues. Like other animals, coral polyps capture and eat food, but the plant cells provide an additional source of nutritious compounds to the coral. These algae give most corals their characteristic brownish-green color. The extra energy from the algae allows corals to secrete a calcium carbonate skeleton. When many living and dead skeletons fuse together over time, a coral reef is formed.
Coral reefs are the largest structures made by living organisms.
National and regional coordinators are responsible for organizing the teams. Each team includes a group of experienced recreational divers. Surveys were carried out between1 April and 30 September, 1998. The survey methods were specially designed for recreational divers, so that training is rapid and organism identification is accurate. Preliminary 1998 Results Almost 40 countries and territories participated in 1998, an increase over 1997.