Coral animals begin life as free-floating larvae, but settle on the sea floor in sedentary colonies. The term "coral" applies both to these animals and to their skeletons, particularly the skeletons of stone-like corals.

Many different organisms, including molluscs, sponges, and worms, help shape reefs, but hard corals and various algae are the major architects. In effect, the corals build limestone, because their skeletons are made of Calcium Carbonate. The skeletons deposited by these corals and other organisms accumulate, along with sand and other debris, to form the backbone of the reef. Over tens of thousands of years, chemical and mechanical changes turn the reef into true rock.

The body of a coral animal consists of a polyp, which is the living portion of the coral. A poly

People harm reefs in lots of other ways:

The location of the Florida Keys makes them particularly vulnerable. They are close to the heavily populated North American coast, and ocean currents place them downstream of the Caribbean basin. The Loop Current, which travels clockwise in the Gulf of Mexico from the Yucatan Peninsula, to the Mississippi River, by Tampa Bay, and ultimately to the Florida Keys, carries stormwater and agricultural runoff containing pesticides, heavy metals, oil, and other toxic waste from more than half of the United States. Even sediment from the Amazon finds its way through the Florida straits. Compounding the problem is the fact that most of the bedrock underlying the islands of the Florida Keys is highly porous limestone, the remains of ancient reefs, through which contaminated waters easily flow in and out. Preliminary studies indicate that ground waters beneath the reefs do contain nutrients, principally ammonia, at levels many times higher than that of normal seawater. These nutrient-rich ground waters can seep into the reef's water columns with each change of the tide.

· Mining of coral rock and sand: These are used for building materials, and coral is mined for jewellery.

· Wear a float coat so you can adjust gear without standing on or sitting on coral. Avoid contact with the ocean bottom, where fragile organisms can live. Try not to kick up sand, which can smother reefs.

Most present-day reefs have probably been growing for 5,000 to10, 000 years. But their continued survival is now threatened. Reefs around the world are now declining at an unprecedented rate--one that far outstrips our understanding of the problem. Few long-term studies of coral reefs have been conducted, and there is considerable debate about the overall health of reef ecosystems. Still, most scientists agree that reefs worldwide are in crisis.

· Mediators of global climate: Corals remove large amounts of carbon from the atmosphere as they grow, actually "fixing" 700 billion kilograms a year. Carbon dioxide is a greenhouse gas that contributes to global warming.

· Enjoy diving on the reef without touching or bumping into it. Control your flippers and snorkels. Even the lightest contact can hurt sensitive polyps.

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Approximate Word count = 3359
Approximate Pages = 13 (250 words per page double spaced)