Coral reef
Say it: KOR-ul REEF
A coral reef is an underwater ridge built over centuries from the limestone skeletons of colonial coral animals, home to some of Earth's richest sea life.
Also: coral reefs
Definition
What is a coral reef?
A coral reef is a large structure on the seafloor made mostly of calcium carbonate, the hard mineral laid down by colonies of tiny animals called coral polyps. Corals are cnidarians, relatives of jellyfish and sea anemones. Each polyp builds a cup-shaped skeleton beneath itself, and over thousands of years the skeletons of countless generations, cemented together by other organisms such as coralline algae, pile up into a reef. The main forms are fringing reefs along a coast, barrier reefs separated from land by a lagoon, and ring-shaped atolls around sunken volcanic islands.
Most reef-building corals live in warm, clear, shallow tropical water because they depend on a mutualism with single-celled algae called zooxanthellae that live inside their tissues. The algae photosynthesize and pass most of the sugars they make to the coral, and in return gain shelter and nutrients. This partnership lets reefs thrive in seas that are poor in nutrients. Reefs cover only a tiny fraction of the ocean floor, yet they shelter a very large share of marine species, often put at around a quarter, which is why they are called the rainforests of the sea. They also protect coasts from waves and support fisheries and tourism.
Reefs are threatened by warming water, which causes coral bleaching, and by ocean acidification, pollution, sediment and overfishing.
Word parts
Where does the term “coral reef” come from?
- coral
- coralGreek korallion, via Latin corallium
- reef
- ridge, ribMiddle Dutch rif
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Terms that go with it
- Coral bleachingCoral bleaching is the paling of stressed corals as they lose the tiny symbiotic algae inside their tissue, most often because the water is too warm.
- MutualismMutualism is a relationship between two species in which both partners benefit, such as flowering plants and the insects that pollinate them.
- Ocean acidificationOcean acidification is the ongoing fall in the pH of seawater, driven mainly by the uptake of carbon dioxide that human activities release into the air.
- BiodiversityBiodiversity is the variety of life in a place or on Earth as a whole, from genetic differences within species to the range of species and ecosystems.
- SymbiosisSymbiosis is a close, long-lasting relationship between two different species that may benefit both, benefit one, or benefit one at the other's expense.
- PhotosynthesisPhotosynthesis is the process in which plants, algae and cyanobacteria capture light energy and store it in sugar built from carbon dioxide and water.
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Checked against
Written for biofideX in plain words, after checking these references:
- NOAA Education: Coral reef ecosystems
- OpenStax Biology 2e, 44.4 Aquatic Biomes
- National Geographic Education: Coral Reefs
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