A look at the ingenious world of corals

A coral colony usually consists of thousands of little coral animals, or polyps, as seen in this picture. Each polyp is like a tiny anemone (or jellyfish on its back) which secretes a calcium carbonate, or limestone skeleton on/in which it lives. A colony may begin with just one polyp, to stretch over many metres in diameter as it grows, adding more and more polyps.

What are corals

Coral polyps, like anemones and jellyfish, are typically partially carnivorous, feeding on any small particle that is floating on the water and brushes against its tentacles. Corals also have microscopic algal cells living within their tissues called zooxanthellae. These algae take the metabolic waste products of the coral as fertilizer, combine them with light (like any other plant) and produce enough food for both the algae and the polyp.

The algae gets food and protection within the polyp, and the polyp gets food from the algae. In this way, the polyp is able to recycle food within itself, being efficient enough to thrive in the nutrient poor waters of the tropical oceans. Coral reefs are in fact one of the most productive natural communities on earth, occurring in clear, shallow tropical waters around the world.

A reef provides food and habitat for fish and also protects the shoreline from erosion. Coral reefs, when healthy, are continually growing, forever strengthening this protective barrier. Reefs protect shallower inshore habitats such as sea grass beds and mangrove systems from incoming waves, and the mangrove systems and sea grass beds protect the reefs from coastal stresses such as excessive nutrients and muddy water. It's all a big system working together.

Reef dwelling organisms often produce biologically active compounds to keep themselves safe from stresses, diseases or predators: possessing unpleasant, poisonous, anti microbial and antiviral abilities. These compounds may be important sources for new natural drugs and medicines for us as well.