A Visit to the Great Barrier Reef
By Awake! correspondent in Australia
The excited chatter of tourists reaches a crescendo as the passenger launch slows down at the end of its 18-mile [29 km] trip from Cairns. Infectious giggles from a group of girls betray their excitement—they are about to set foot on Green Island, a major attraction on Australia’s Great Barrier Reef.
‘But what is a barrier reef?’ you might ask. ‘And what is so great about this one that it merits such a title?’
The Great Barrier Reef is the largest system of coral reefs in the world. It runs for some 1,200 miles [2,000 km] along the coast of Queensland, Australia’s northern state. Individual reefs vary greatly in size, but some of the larger ones are up to a mile [2 km] wide and 15 miles [24 km] long. The total area of the Great Barrier Reef Marine Park is 135,000 square miles [349,000 sq km], with distances from the Australian coastline ranging from 10 miles [16 km] to over 200 miles [300 km].
The term “barrier” is used to describe a reef that runs parallel to a coastline but lies farther out than the closer fringing reef. Another type of reef is the atoll, distinguished by its resemblance to a doughnut, being ring-shaped with a lagoon in its center.
The Barrier Reef’s climate is also great—warm in winter months, with the rest of the year’s tropical heat tempered by refreshing sea breezes. Any claim to greatness must also include the reef’s role as an immense sanctuary for birds and marine animals. It is renowned for its variety of edible fish, such as tuna, grouper, and coral trout, to say nothing of its big-game fish—black marlin, swordfish, barracuda, and shark.
Some of the world’s most spectacular shells are found on the reef—big ones too. Giant-clam shells weighing more than 500 pounds [230 kg] are not uncommon. And some of the world’s largest oysters have been harvested from the reef. Even pearl shell has been gathered along its northern section.
Of spectacular greatness is the magnificent color of the coral itself. Vying with this are the dazzling colors of tropical fish that abound in its waters: vivid contrasts of blue and orange, black and gold, even scarlet and green. Also causing astonishment are the bizarre shapes of these fish, strikingly displayed as they dart or glide in and out of the beautiful, complex coral structures.
The Wonder of Coral
Coral is the limestone “house,” or skeleton, manufactured by a tiny sea animal called a polyp. While alive, it builds the coral “house.” When the little polyp dies, it leaves the skeleton behind, bequeathed as a legacy to future generations. At birth the minute polyp larva swims about freely, but soon attaches itself to coral left behind by its predecessors. Now firmly anchored, it grows into a tubelike shape, with a mouth at the top of the tube from which small tentacles grow. The polyp then begins its diet, consisting of the animal constituents of plankton, mainly small crustaceans and fish larvae.
From this point on, it builds industriously, taking calcium salts from the seawater and secreting a hard, limestonelike substance to form a stony cup at its “feet,” or base. Successive generations build on these cuplike skeletons, which take different shapes and colors according to the type of coral organism doing the building.
The result is a striking variety of beautiful coral, giving rise to such picturesque names as lace coral, mushroom coral, staghorn coral, star coral, and brain coral, to name just a few. And the breathtaking colors of live coral may be white, yellow, green, brown, orange, pink, red, purple, blue, or black.
So this is the building block of the Great Barrier Reef: colorful, fascinating coral. And though the main types found there are the rounded star and brain corals as well as the delicate staghorn, there are said to be at least 350 different kinds of coral on the reef! The thickness of coral forming the reef varies. Two bores sunk on one coral island reached a depth of 400 feet [120 m] before finding sand.
The Beauty Is Under Water
Surface coral is not very attractive, being composed of only dead and broken coral. It is the living coral in deeper pools that has the breathtaking color. Therefore, the real beauty of the reef can only be seen through a glass-bottomed boat or by snorkeling and scuba diving.
The water surrounding the reef is crystal clear, so that features as deep as a hundred feet [30 m] are easily seen by enthralled passengers seated around the edges of the large glass panel in the floor of specially built boats. Even the deepest coral can easily be seen from the water’s surface, for reef corals grow best in sunlit water, and reef-building slows as the water gets deeper than 35 feet [11 m].
The Reef’s Enemies
Man himself is sometimes the greatest enemy of natural wonders such as the Barrier Reef. Consequently, many are pleased that the Australian government has so far prohibited regular oil drilling on the reef, although some exploratory drilling has been done.
There is, however, an “enemy” that is not easily controlled: a starfish known as the crown of thorns. Its name is derived from its appearance; it has as many as 23 arms radiating from a central body, like the spokes of a wheel. Its entire surface is covered with thousands of sharp spines that are toxic to humans. It is one of the largest starfish in the world, reaching up to 28 inches [70 cm] across.
Crown-of-thorns starfish feed on live coral, that is, on the living polyps that are still manufacturing the coral, and they have caused extensive damage to parts of the reef. These starfish have been the subject of intense controversy since they were first observed in 1962.
Some take the alarming view that the entire Barrier Reef is at risk, and they issue warnings such as ‘No Reef by the Year 2000.’ On the other side, there are scientists who claim that this infestation is natural and necessary, likening it to the long-range benefits of bushfires or forest fires. They point out that so far infestations of the starfish have been confined to one third of the reef.
Whatever the personal view taken about this spiny starfish and the damage being done to the coral reef, most agree that more thorough scientific research is needed. Thus, over the last few years, what has been called the most intensive study of a marine animal ever conducted in Australian waters has been under way. What the final outcome will be, time alone will tell. Meanwhile, if you are able to take a trip down under, a visit to Australia’s fascinating and colorful Great Barrier Reef will no doubt deepen your appreciation for the wonders of creation.
[Map/Pictures on page 24, 25]
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Great Barrier Reef
Photos of coral: By courtesy of Australian Overseas Information Service