#8: Florida Keys Reef, United States
A National Treasure, On The Ropes
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The only barrier reef along the continental U.S. is also one of the world's most threatened. Hurricanes, pollution and warming sea temperatures have decimated the coral population off the Florida Keys, from about 50 percent coverage on the reefs in the 1970s to less than 10 percent today. (NOAA's National Ocean Service/flickr.com)
For centuries, the shallow waters just off the islands of the Florida Keys have offered many of the perfect conditions for coral reef-building: clear, tropical waters with relatively warm temperatures and plenty of wave action, which whisks away waste and brings in oxygen and plankton, which are needed by the animals that live on the reef.
Christ of the Deep.
That has helped the reefs that have grown in what is now the Florida Keys National Marine Sanctuary, which stretches from Miami to Dry Tortugas National Park, draw hundreds of thousands of snorkelers and scuba divers every year, especially those who come to get a glimpse of stingrays, moray eels and lobster walking the seafloor or the 9-ft.-tall, 4,000-pound bronze statue known as "Christ of the Deep."
Off the coast of Key West, divers can see real shipwreck sites and artificial reefs like Stargazer, a series of metal cutouts of star constellations (each of which weighs between one and four tons) that now lie at the bottom of the sea, forming the base for new reefs.