THE GREAT BARRIER REEF
Within the tropical parts of the great South Sea are submarine gardens that in the beauty of their floral forms and their richness of coloring rival the most elaborate flowerbeds made by man; in color and variety they are fairy regions of exquisite living animal flowers. One of the greatest and most attractive of these sea gardens lies off the coast of Australia.
Of all the wonderful animal structures in the world the Great Barrier Reef of Australia is the most remarkable. It consists of a chain of coral islands and reefs parallel to the east coast of Queensland. This great reef is about twelve hundred miles long, and the distance from the mainland to its outer border is from ten to more than one hundred miles. It is far enough off the coast to leave a wide channel between the reef and the shore.
Since it is well charted this channel is the route taken by many vessels. It is admirably furnished with lighthouses and light-ships, and is protected from the huge rolling billows of the ocean by the reef itself. There are several breaks in the reef through which vessels can pass out into the open ocean.
This mighty barrier, the work of coral polyps, is of special interest not only on account of the curious shapes and varied kinds of sea life it presents, but because of the commercial value of its products. The bêche-de-mer, pearl, oyster, and sponge fisheries yield an annual revenue of upward of half a million dollars, and when all of the resources of the reef are properly exploited the returns will be more than doubled.
The habitat of the reef-building coral is in clear tropical waters. The polyps thrive best near the surface; they cannot live at a depth exceeding one hundred and twenty-five feet. The reef-building coral must not be confounded with the precious, or red, coral, which flourishes in a muddy sea-bottom and is found chiefly in the Mediterranean Sea.
When alive and in the water, coral polyps present a variety of beautiful forms and colors. Living polyps are composed of limestone skeletons covering and permeating a soft gelatinous substance which corresponds to the flesh of animals. When the polyps are removed from the water this soon decomposes and disappears; in certain species a part of it flows off as a thick liquid.
Fish fantastically striped and of brilliantly variegated colors are seen swimming among the coral. In tropical waters many of them have fascinating colors and patterns. By simulating the colors of the coral polyps they escape the species that prey upon them.
The different kinds of coral are generally designated by common names according to the different objects which they resemble. Thus, by similarity of form we have brain coral, organ-pipe coral, mushroom coral, staghorn coral, etc.
Some of the islands and reefs are the homes of sea fowl and at the nesting season are literally covered with their eggs. These fishers of the sea have marvellously well-developed faculties for location, since each bird goes directly to her nest when returning to the islands. As night approaches, when all the birds seek the land, their wild cries are deafening.
Some of the islands are turned to profitable account by the export of guano. On Raine Island, so extensive are the deposits of guano that a railroad has been built to facilitate handling the product.
Bêche-de-mer, or trepang, is a name applied to the flesh of certain sea slugs or sea worms found in the Indian seas. Of this substance great quantities are gathered annually. In the water the animals resemble huge cucumbers, and they are therefore sometimes called "sea-cucumbers." They are found clinging to the rocks below low-water mark, and are from one to four feet in length. Their food consists of microscopic shell-fish which live upon the coral rocks.
The Great Barrier Reef of Australia, the most remarkable animal structure in the world
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The trepang exported from this section requires considerable care in preparation. After being gathered from the rocks they are cleaned, boiled, and partly dried in the air; then they are smoked with mangrove wood until dry and hard. The best class of trepang is packed in tin cases to keep it perfectly dry, as moisture ruins it. The product is marketed chiefly at Hongkong, where it is used in making the gelatinous soups for which the Chinese are so famous.
The pearl-shell fisheries yield products of considerable value. The average depth from which the mother-of-pearl shell is gathered is seven or eight fathoms. Twenty fathoms represents the greatest depth in which divers, even in their diving suits, can work, so great is the pressure of the water upon them.
The fishery is carried on chiefly for securing the shells, the finding of pearls being of secondary importance, since only about one shell in a thousand contains a pearl of much value. The shells themselves bring in the market from three hundred to eight hundred dollars per ton according to quality and size, and are used chiefly for making buttons and small ornaments.
The Cairn Cross Islands, a little coral group midway between Cape Grenville and Cape York, are especially interesting as the home and nesting-place of the Torres Strait pigeons. These large white pigeons are highly esteemed for the table. They gather at the islands during the month of October and remain until the end of March. The nests are usually built in the forked branches of the mangrove trees that form extensive thickets along the coast. Each nest contains two white eggs.
The Australian jungle-fowl or scrub-hen also frequents these islands as well as the mainland. The nests of these birds are large and unique. They consist of huge mounds of dead leaves, grass, sticks, and soft earth piled together by the adult birds in shaded and sequestered places. The mounds are about twenty feet in diameter and from ten to fifteen feet high. Several pairs of birds generally unite in their construction.
When the mounds are completed the birds burrow holes in the centre and deposit their eggs, which are left to be hatched by the moist heat engendered by the decaying vegetation. Forty or fifty brick-red colored eggs as large as those of a turkey are sometimes found in a single nest. Both the eggs and the parent birds are excellent eating.
The Australian bee-eater, a bird of attractive plumage, is found all over the northern islets of the Barrier Reef. It has a long, sharp curved bill and two long, narrow feathers in its tail. Its beautiful green plumage, varied with rich brown and black, and vivid blue on the throat, makes it an attractive bird.
The sea-anemones of the Great Barrier Reef are remarkable for both beauty of color and structure; some of them measure four or five inches across the expanded disk. In Torres Strait are seen brilliant sea-anemones around the border of whose disks are jewel-like clusters. These beautiful sea animals present the appearance of delicately tinted flowers adorned with the most exquisite gems.
Starfish and sea-urchins of all descriptions are found in immense numbers. The five-rayed varieties of starfish are universally condemned as insatiable foes of the oyster family, and the oyster cultivators destroy all they can find. To dismember the body of the starfish by pulling off the finger-like rays does not kill the animal, for not only does each fish produce new rays but each ray will produce a new starfish. The predatory starfish fastens itself to both valves of the oyster, forces them open, and consumes the fleshy part. It is destructive not only to oysters but to clams, mussels, barnacles, snails, worms, and small crustacea as well.
The variety of sea life about the great reef is legion. Among the bivalves the most remarkable for the size and weight of the shells are the tridachna and hippopus. In some localities they are so numerous that their shells have been burned to make lime. A pair of tridachna valves often weighs several hundred pounds.
To the naturalist the Great Barrier Reef is an object of special attraction.