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Tuesday, August 21, 2012

The Great Barrier Reef

The Great Barrier Reef
The Great Barrier Reef, the largest living structure on Earth, is the product of billions of tiny organisms called polyps which secrete calcium carbonate during photosynthesis to form coral. Soft corals cling to hard corals, algae and sponges paint the rocks, and every crevice is a creature's home. But this fragile coral colony is beginning to crumble, battered by the effects of climate change, pollution and man made disasters.
Corals grow best in shallow, clear and turbulent water with lots of light to support photosynthesis. The Great Barrier Reef formed 25 million years ago when coral larvae in the Indo-Pacific caught south-flowing currents and grabbed footholds off Australia's eastern edge where conditions are ripe for coral flowering. Slowly, rocky colonies grew and spread along the seafloor. Today, the reef stretches for more than 2,600km and covers an area of 25,900sqkm; wide ribbons of the Great Barrier Reef divide the continental shelf from the deep waters of the Coral Sea.
Since the reef first found its footing, ice ages have come and gone, tectonic plates have shifted, and ocean and atmospheric conditions have fluctuated wildly. The reef has undergone many iterations, being defaced and repopulated at nature's whim. Its resilience is undeniable; after every flux, the coral has rebounded and life has returned. Now, however, all the factors that allow the reef to grow are changing at a rate the Earth has never before experienced.
Of course, for the two million tourists who visit the reef each year, the promise of an underwater paradise teeming with life is still fulfilled. The reef is host to 5,000 types of molluscs, 1,800 species of fish (like the humphead wrasse, pictured – a fish that can reach 2m in length) and 125 kinds of sharks. Divers often spot moray eels, white tip reef sharks and stingrays; at this underwater theatre, nature delivers a superb performance.
The blemishes caused by climate change and human error are visible to those who know where to look. The reef bears a two-mile-long scar from a collision with a Chinese coal carrier in April 2010. Other ship groundings and occasional oil spills have marred the habitat. Sediment plumes from flooding on the mainland nutrients from agriculture and development also damage the ecosystem. To sustain the reef's diversity of sea life, as pictured at Pixie Pinnacle (one of the Great Barrier Reef's signature dive sites), coral polyps must be allowed to flourish. (David Doubilet/National Geographic Stock) 

(BBC Travel) 

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