At first glance, coral simply looks like either a rock (if it is hard coral which has an outer skeleton made of limestone) or a plant (if it is soft coral which does not produce a limestone skeleton). But actually, coral is a colony of tiny animals called coral polyps. Each coral polyp can roughly be described as having a body (that looks like your wrist and hand pointing up) with tentacles (which look like your fingers) and a mouth (imagine a hole in the center of your palm). Living inside the body tissue of each coral polyp are microscopic plants (called “zooxanthellae”). These tiny algae produce nutrients for the polyp. The coral returns the favor by providing the algae with a place to live. Algae come in a rainbow of colors. It is the algae living inside the coral, which give color to the coral.

Jacinto, N. (2010, September 23). Philippine coral reefs-in hot water. The Philippine Star, pp. B-6, B-7.