Philippine Reefs

In geological terms most Asian reefs are quite young. They originated after the last ice-age, when seawater levels were 120 m. lower than today. The slowly rising level of the warm tropical waters created an excellent environment fro the forming of corals and reefs.

Tropical reefs are mainly built from corals, primitive animals closely related to sea anemones. Most of the coral types that contribute to reef

construction are colonial in nature, numerous individuals or polyps. They produce calcareous stony skeletons, ones grow on top of them and so it continues. Actually only the outermost layer of the growing reef is alive.

There are about 450 species of reef-building coral in the seas around the Philippines. Corals grow slowly, adding about 1-10 cm (0.4 - 4 inch) growth in a year. Once over a certain age they start being able to reproduce, releasing tiny forms that float freely among the plankton for a few weeks until settling to continue the growth of the reef. The forms coral create as they grow vary enormously according to the species and to the place on the reef where it grows.

Colonies range in size from arm of plates, tables or delicate leafy ronds. The growth and health of corals depends for a great deal on microscopic plants, called zooxanthellae. These are packed in millions into the living tissues of the most reef-building corals (and of various other reef animals, such as giant clams). Although reef corals also capture plantonic organisms from the water, a significant amount of their food comes directly from the zooxanthellae. It is precisely for this reason that most coral growth is in shallow clear water, the preferred environment of the zooxanthellae.