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Coral reef

en.wikipedia.org/wiki/Coral_reef

Coral reefs are diverse underwater ecosystems held together by calcium carbonate structures secreted by corals. Coral reefs are built by colonies of tiny animals ...

Coral Reef | Basic Facts About Coral Reefs | Defenders of Wildlife

www.defenders.org/coral-reef/basic-facts

Coral reefs are some of the most diverse ecosystems in the world, housing tens of thousands of marine species. About one-third of all marine fish species live ...

Corals and Coral Reefs | Smithsonian Ocean Portal

ocean.si.edu/corals-and-coral-reefs

Coral reefs are the most diverse of all marine ecosystems. They teem with life, with perhaps one quarter of all ocean species depending on reefs...

NOAA CoRIS - What are Coral Reefs

www.coris.noaa.gov/about/what_are/

Dec 16, 2014 ... Coral reefs are unique (e.g., the largest structures on earth of biological origin) and ... Stony corals (scleractinians) make up the largest order of ...

What Are Coral Reefs? | Coral Facts - Live Science

www.livescience.com/40276-coral-reefs.html

Oct 8, 2013 ... Coral reefs are large underwater structures composed of the skeletons of coral, which are marine invertebrate animals.

Coral Reefs | Coral Reef Alliance

coral.org/coral-reefs-101/coral-reef-ecology/

From reef-building corals to large, predatory fish like sharks, coral reefs are one of the most fascinating, complex, and biologically diverse ecosystems.

Coral Reefs

life.bio.sunysb.edu/marinebio/coralreef.html

Coral reefs are the most diverse and beautiful of all marine habitats. Large wave resistant structures have accumulated from the slow growth of corals.

Coral Reefs - National Geographic

video.nationalgeographic.com/video/coral-reefs

Coral reefs are the foundation of many marine ecosystems—and they are in danger.

Corals, Coral Pictures, Coral Facts - National Geographic

animals.nationalgeographic.com/animals/invertebrates/coral/

Coral organisms, called polyps, can live on their own, but are primarily associated with the spectacularly diverse limestone communities, or reefs, they construct.

Coral Reef Facts and Information

www.coral-reef-info.com/

Facts and information about coral reefs; including reef structure, marine life, and distribution.

Answers
Coral reefs are underwater structures formed from the calcium carbonate secreted by corals.