Australia's renowned coral formations are found in the Great Barrier Reef, a popular destination for scuba divers out to explore more than 400 species of corals, and 1500 tropical fish species. This type of reef borders shorelines, but there is a separation from the land by open, deep water.
Fringe reefs are created when corals grow near shorelines and around islands. The corals grows outward from the land, projecting into the water. These are the most common type of reef structure, with no water between the reef and the land mass which it surrounds. Hanauma Bay on Oahu in Hawaii shows a clear example of fringing reef.
An atoll is usually, but not always, a ring of coral formations around a lagoon. Sometimes these first form as fringes around volcanoes that submerge, leaving behind only the atoll. Section breaks in an otherwise round atoll will allow entry to the central lagoon. Some can emerge as chains, such as those found in the 26 naturally occurring atolls that make up the Maldive Islands south of India.
Seven defined zones make up each reef structure. These include the sheltered reef-flat closest to shoreline; the reef-crest which is the highest point and most exposed to oncoming waves; the fore-reef extending from the outer slope to the low tide mark; and the stabilizing buttress zone which dissipates unabated waves. The deep fore-reef is the deep water area lying beyond the reef structure, and the lagoon zone is where water pools between the land and the reef-crest.
According to some scientists, since the 1980's rising global temperatures have contributed to a more rapid decline of some coral reefs. The crown-of-thorns seastar has also raised concerns. Other causes of harm to these fragile worlds are negligence or ignorance by humans: dynamite fishing, waste dumping, harmful runoff and sludge accumulations from land forms. Careless boaters, divers who break apart large sections, and other invasive forms of attack on the reefs have harmed them in ways that will take hundreds of years to repair, if it happens at all. The thousands of species of coral now in existence must have clean, clear water, strong light, and consistently warm temperatures to grow. If any of these factors is missing, the corals will disappear. If that happens, thousands of species of fish and other marine life will be affected detrimentally as well. We can do our part through education, and by helping to spread awareness so that we do not lose these exquisite and important elements of the world's oceans.
