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Corals are colonial marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.
Oct 19, 2023 · Learn about coral, a colonial animal that forms reefs with algae and provides habitat for many marine species. Find out how coral reefs are threatened by pollution and warming waters, and how they benefit people and the ocean.
May 31, 2024 · Learn about coral, a variety of invertebrate marine organisms with skeletons of different forms and colours. Find out how coral reproduces, feeds, and forms reefs and atolls in various oceans.
- The Editors of Encyclopaedia Britannica
- Polyps, Colonies, and Reefs
- Color and Bleaching
- Feeding
- Threats to Survival
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Coral polyps are tiny, soft-bodied organisms related to sea anemones and jellyfish. At their base is a hard, protective limestone skeleton called a calicle, which forms the structure of coral reefs. Reefs begin when a polyp attaches itself to a rock on the sea floor, then divides, or buds, into thousands of clones. The polyp calicles connect to one...
Coral polyps are actually translucent animals. Reefs get their wild hues from the billions of colorful zooxanthellae (ZOH-oh-ZAN-thell-ee) algae they host. When stressed by such things as temperature change or pollution, corals will evict their boarders, causing coral bleaching that can kill the colony if the stress is not mitigated.
Corals live in tropical waters throughout the world, generally close to the surface where the sun's rays can reach the algae. While corals get most of their nutrients from the byproducts of the algae's photosynthesis, they also have barbed, venomous tentacles they can stick out, usually at night, to grab zooplankton and even small fish.
Coral reefs teem with life, covering less than one percent of the ocean floor, but supporting about 25 percent of all marine creatures. However, threats to their existence abound, and scientists estimate that human factors—such as pollution, global warming, and sedimentation—are threatening large swaths of the world's reefs.
Learn about corals, the tiny animals that build spectacular reefs in tropical oceans. Discover how corals feed, reproduce, and cope with climate change and human impacts.
Oct 19, 2023 · Learn about the importance, diversity, and threats of coral reefs, the rain forests of the seas. Find out how climate change, ocean acidification, and human activities affect coral reefs and what can be done to protect them.
Jun 19, 2024 · Coral reef, ridge or hummock formed in shallow ocean areas by algae and the calcareous skeletons of coral polyps and other coelenterates. A coral reef may grow into a permanent coral island. Often called ‘rainforests of the sea,’ coral reefs are home to a spectacular variety of organisms.
Nov 7, 2017 · What are coral reefs? Coral can be found in tropical ocean waters around the world. But how much do you know about reefs and the tiny animals—polyps—that bui...
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