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Corals and Coral Reefs

A Round-Up of Coral Facts and Information

By , About.com Guide

Coral reefs provide some of the most spectacular underwater scenery and marine life biodiversity in the world. Here you can learn what coral is, how coral reefs form, and threats to coral reefs.

1. What Is Coral?

Mushroom Coral / NOAANOAA, http://oceanexplorer.noaa.gov/gallery/
Corals are animals in the Phylum Cnidaria. Cnidarians also include sea fans, sea pansies and anemones. Corals are in the Class Anthozoa, and can be divided further into the stony corals (Order Scleractinia), the builders of coral reefs, and soft corals (Order Alcyonacea), which are soft or leathery in texture.

2. How Do Coral Reefs Form?

Coral Reef in St. Croix, U.S. Virgin Islands / NOAANOAA, http://www.noaa.gov/features/climate/coralreefwatch.html
Coral reefs are composed of animals called stony corals. Corals are made up of tiny organisms called polyps, which have a skeleton made of calcium carbonate (limestone). As the polyps live, reproduce, and die, they leave their skeletons behind. This forms the structure of coral reefs.

3. The Coral Reefs Habitat

Spanish hogfish at coral reef in Florida Keys National Marine SanctuaryFlorida Keys National Marine Sanctuary
Coral reefs are habitats with a huge amount of biodiversity. Around a healthy coral reef, many species of invertebrates, fish and other animals will thrive. While the majority of coral reefs are found in tropical and sub-tropical water within the latitudes of 30 degrees north and 30 degrees south, there are also deep water corals in colder regions. There are 3 main types of coral reefs: fringing, barrier, and atolls.

4. Threats to Coral Reefs

Coral bleached at St. Croix (NOAA photo)NOAA
Two major threats to coral reefs are coral bleaching and ocean acidification. Coral bleaching is when coral polyps shed the zooxanthellae that give them their color. Warming water is the most likely culprit. Ocean acidification is a related phenomenon, caused by global warming and the changing of the ocean's pH as a result of absorption of carbon dioxide. Both of these threats can have devastating effects on a reef, and cascading effects on the marine life that live there and those who depend on reefs for fishing, tourism and food.
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