Coral Reef
by Staff EditorTo most people, coral reefs are one of the most mysterious ocean phenomena on earth. What purpose do they serve beyond captivating us with their rare beauty? Where do they come from? And just what exactly are they?
Coral reefs are one of the most valuable marvels of the sea. Known as the rainforest of the sea, they are usually found in the warm, shallow waters of tropical oceans. Reefs serve purposes as diverse as offering food and shelter to fish to protecting the earth's shorelines from erosion. Compounds found in the corals can also be useful in the making of many natural drugs and medicines. Reefs are also appreciated as important land builders in tropical areas responsible for forming islands and reconstructing shorelines.
The genetic makeup of a coral reef is complex. A reef is made up primarily of corals that combine with algae called zooxanthellae. These corals reproduce both sexually and asexually and the calcium deposits found in the polyps can grow a colony of corals from a single polyp. While corals make up much of the reef's structure, they are not the only part. Coralline algae glue the various corals together and other organisms such as tubeworms and mollusks use their hard shells to construct many kinds of reefs.
Sensitive to environmental changes, human factors have the most detrimental effect on coral reefs. Increasing tourism and migration to reef-rich areas puts them in harm's way, as do environmental changes, hurricanes, bleaching and disease.
The coral reefs of the western Pacific are more varied than those of the Atlantic and Caribbean, with up to 85% more species.
There are three principle types of coral reefs: fringing reefs, barrier reefs and atolls.
Fringing Reefs:
Fringing reefs grow in shallow waters and usually border the coastline. They consist of zones that are differentiated by their depth, their structure and the plant and animal life that thrives there. These regions include the reef crest (where the waves break over the reef), the fore reef (a region of medium energy) and the spur and groove or buttress zone (a region of coral that includes rows of corals with sandy canyons or passages between them).
Barrier Reefs:
Barrier reefs are separated from land by a lagoon. They grow parallel to the coast and tend to be large and unbroken. They also include regions of coral formations that include zones found in fringing reefs, patch (small) reefs, back reefs (the shoreward side of the reef) and bank reefs (reefs that occur on deep bottom irregularities). They can also include reef flats and reef crests that run parallel to the coast and are protected from waves. Barrier reefs also include a coral terrace (a slope of sand with coral peaks) that is followed by second coral terrace and a drop into deeper waters.
Atolls:
Atolls are annular reefs that develop at or near the sea's surface when islands surrounded by reefs sink. They are circular in shape and usually separate a lagoon. The two types of atolls are deep sea atolls that rise from deep within the sea and those found on the continental shelf.
