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Stunning photos of coral reefs around the world

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Coral reefs are underwater structures composed of reef-building colonial marine invertebrates held together by calcium carbonate. As some of the most ecologically diverse marine environments in the world, these sensitive ecosystems are increasingly under threat from climate change, rising sea temperatures and human activities such as over-fishing, ocean acidification and water pollution. We explore the beauty of these spectacular underwater havens in pictures.

(Pictured) The Great Barrier Reef, located off the coast of Queensland, Australia, is listed among the natural wonders of the world.

© Pniesen/Getty Images
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