Corals are diverse groups of invertebrate animals. Coral polyps are tiny, soft-bodied organisms that are related to jellyfish and sea anemones.
Different species of coral are found in different habitats and different locations around the world. Hard corals like lobed star coral and pillar coral are reef-building corals. Colonial hard corals, consisting of hundreds to hundreds of thousands of individual polyps, are cemented together by the calcium carbonate “skeletons” they secrete. As colonies grow over hundreds and thousands of years, they join with other colonies and become reefs. Some of the coral reefs on the planet today began growing over 50 million years ago.
Soft corals do not produce a rigid calcium carbonate skeleton and do not form reefs, although they are often found in reef ecosystems. Soft corals are also colonial animals. Often, what appears to be a single large organism—resembling trees, bushes, fans, and whips—is actually a colony of individual polyps combined to form a larger structure.
Coral reefs teem with life. Although they cover less than one percent of the ocean floor, they support about 25 percent of all marine creatures. Corals are particularly vulnerable to the effects of human activities including pollution, climate change, sedimentation, and fishing. Under the Endangered Species Act, more than 25 coral species are listed as threatened or endangered.
NOAA Fisheries works to better understand and conserve coral species and coral reef habitats both domestically and internationally.
Species News
Coral reef ecosystems, like this reef on Hawaiʻi Island, are more likely to persist under ocean warming when local human impacts originating from land and sea are reduced simultaneously. Credit: Arizona State University/Greg Asner
Euphyllia paradivisa coral at Tutuila, American Samoa. Credit: Douglas Fenner
Restored staghorn coral (Acropora cervicornis) at Looe Key reef in the Florida Keys National Marine Sanctuary. Staghorn coral, along with elkhorn coral and star corals, built Caribbean coral reefs over the last 5,000 years. NOAA Fisheries and partners are using a variety of innovative techniques to study, protect, and restore these threatened corals. Credit: U.S. Geological Survey
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Research
Juvenile Coral Abundance Across the U.S. Pacific Influenced by Depth, Heat Stress, Coral Cover, Suitable Substrate, and Human Density
Our results also suggest coral density is dependent on several factors, including and the number of…
Ocean Currents Magnify Upwelling and Deliver Nutritional Subsidies to Reef-Building Corals During El Niño Heatwaves
Results reveal how large-scale ocean-climate interactions affect reef ecosystems thousands of…
Ocean Currents Magnify Upwelling and Deliver Nutritional Subsidies to Reef-Building Corals During El Niño Heatwaves
Results reveal how large-scale ocean-climate interactions affect reef ecosystems thousands of…
Oceanic Productivity and High-Frequency Temperature Variability—Not Human Habitation—Supports Calcifier Abundance on Central Pacific Coral Reefs
Our results reveal that human habitation is no longer a primary correlate of calcifier cover on…
Understanding Ocean Acidification
Learn how our oceans are absorbing increasingly more carbon dioxide from the atmosphere, leading to lower pH and greater acidity.
