The Great Barrier Reef is the biggest coral reef of the world. It is situated off Queensland, in Australia. It extends over 2600 km and covers 357000 km ². It is formed by islands, by small islands and by atolls and represents the eighth wonder of the world: natural marvel which draws a turquoise blue line, parallel to the coast east of Australia. It is not a barrier strictly speaking. It is a multitude of small reefs and small islands. It was called barrier because above these reefs, there is very little water. The first European to discover the Great Barrier Reef was James Cook, who ran aground above it in 1770; beautiful way of discovering it! Financially speaking, the tourism connected to the coral reef (diving but also sailing, flying by plane) enables the living of a whole part of this state and represents a most significant gain for the country. To protect this treasure registered on the heritage of the UNESCO, almost the totality of the site is watched since the 1970’s by the Great Barrier Reef Marine Park.3.

An island is a space of ground surrounded with water. An island is a set of very small islands. An atoll is a coral island in the shape of ring surrounding a lagoon. Coral reefs result from the accumulation of seaweeds limestone, of oysters, corals. The cliff barrier is situated at a certain distance of the bank. Whatever are the coral reefs of the world, they adopt generally the same forms. Factors influencing the growth of corals are waves, similar sea currents, temperature of the water, the light. 2600 coral reefs establish the Great Barrier. The coral is a set of small calcareous polyps of the warm seas, living in colonies and training cliffs it established by the calcareous skeletons of billions of these small polyps of coral put down in the course of thousand years. It is in fact the only association of an animal and a vegetable, which cannot feed the one without the other one. It explains the rarity and the big fragility of coral reef, the coral grows on the calcareous rests of its predecessors fed by warm, clear and little deep waters, rich in nutriments that is why it is always difficult to know the coral as a stone or an animal. Its nature would rather be the one alive stone!

The submarine world of the coral reef offers wonderful colours.This paradise shelters various sorts; more than 400 corals, different by their sizes, shapes and colours, more than 1500 sorts of fishes and shellfishes and 4000 of molluscs. It is the housing environment of several endangered species such as Dugong, green tortoise and tortoise loggerhead (big tortoise of the warm seas, whose scales are very popular). We can find an incalculable number of fishes of various colours, seaweeds and corals, sharks of coral (don not worry,

these are not dangerous), turtles, lines (taiemanta) of napoleons, clown fishes (as Némo), starfishes, cetaceans but also one stream of colored tropical fishes. We can also meet some rare dangerous sorts, as jellyfishes, stone-fishes or the others more classic as groupers or moray eels. There are also 350 sorts of echinoderms (sea urchins, sea cucumbers and starfishes), 500 sorts of different seaweeds and 4000 varieties of (sponges).

Unfortunately a starfish is devouring corals destroying little by little the barrier, the scientists seeming powerless in front of this problem. This starfish, "Crown-of-Thorns” attaches to the coral. When the number becomes too important, the coral sees itself consummate faster than it grows and the degradation of the cliff becomes then inevitable. They are particularly harmful in shallow water: they break corals and can kill whole cliffs of alive corals, what reduces the total surface occupied by these organisms.Varied factors destroy coral reefs and threaten their survival. The over fishing, the pollution, the farming and territory planning during the last two centuries favoured, in a direct way or not, the changes in this ecosystem, what accelerated the loss of sorts.The Great Barrier being situated relatively near to the coast, it is directly exposed to any forms of pollution of the ocean coming from lands and in particular from rivers. The numerous cultures of sugar canes, in particular, as well as the other forms of exploitations of the region of Queensland, generate waste but an even bigger danger watches for this fragile group: it is the global warming. Indeed, corals to grow need water, the temperature of which is included between 18 and 28 °. Numerous sorts are already at present in their upper threshold of temperature. Consequent pieces of corals with certain places went pale during the summer, 1998 and 2002. The various factors of stress as a low salinity, a too low or too much raised temperature, an air exhibition and an exhibition in the cyanide engender the whitening of coral reefs. So, the world climate change aggravated their state, what complicates the management of their survival.

The Great Barrier Reef can be admired after leaving from many cities off the coast of the region of Queensland, but the most popular point of departure remains the city of Cairns. The entire city lives moreover on the tourism of the big barrier. It is of course by boat that we can reach it. Once arrived near the coral reef, the simplest way to approach "Nemo" is to shoe palms and to arm oneself with a mask and with a snorkel. In certain places, the cliff is not even in a meter of the surface. We can admire hundreds of fishes there effortlessly. There are various sorts of dive:

● The diving or scuba diving with bottles ". Impressive discovery of sea bed allowing observing fishes and corals.

● The snorkelling, "or plunge with snorkel". For those who do not too much like feeling all this water over the head, there are boats semi - immersed, with a glass hull which allows to see sea bed while staying dry. The beauty of this sea bed, the density and the variety of the life which crosses them offer an incomparable show and justify the world reputation of this place. A site so exposed to the tourism and representing a financial stake has to be closely watched and kept: the Australian authorities know the sense of the word ecology and are not certainly the last ones in terms of environmental measures; the Big Barrier is classified on the list of the world heritage for more than twenty years and its global reputation, its economic weight and the uncountable lovers of the sea give her a constant attention which can only guarantee her a solid support and a serene future. The tourism is naturally in double sharp edge. The millions of tourists and divers who cross cliffs have a negative impact. A "tax of cliff" of 25 Australian dollars (approximately 16 euro) also contributes to the preservation of the Big Barrier. From this point of view, the important tourist flow brings in a way a security of quality and attention towards the site. In return it is evident that the continuous presence of visitors "use” necessarily cliffs: pollution of boats, knocks of palms of the divers on the coral, the disturbance of animals.

The Australian Coral reef had already suffered of the gigantic floods which covered a part of the State of Queensland (northeast) at the end of December and the beginning of January. Fragments, sediments, pesticides and other dirts were rejected into the sea, off the northeast coast. Yasi, a cyclone of maximal intensity, struck a portion of this coast, in the South of Cairns, which is the front door to numerous vacationers towards the Great Barrier Reef. Fragments of corals reduced to crumbs by the cyclone were already back on beaches and the authorities of the marine park of the Great Barrier Reef consider that the Barrier could put ten years to recover from these two natural disasters. «Cyclones are regular climate-related events, which affect in a very strong way the ecosystem of coral reefs. In this region, it is on average up to four or five cyclones a year but of more or less big importance. Fortunately these have not only a destructive effect on the coral ; they also allow "to remodel" regularly the Big Barrier, engendering a revival of the cliffs and a variety of the alive sorts always maintained.

THE ENDThomas, Teddy, Florian & Jordan.