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Corals

Many people think of coral as hard, rock-like formations that attract abundant, diverse marine life. In fact, corals are tiny marine animals called polyps that live together in colonies.

Reef-building corals create habitats for many other organisms. Coral reefs are highly diverse and unique around the world, providing shelter and sustenance for abundant fishes and other marine life. (Woods Hole Oceanographic Institution)

Key Takeaways

Corals are small animals that build structures ranging from sprawling tropical reefs to slow-growing deep-sea communities far below the sunlit zone.
Reef-building corals support exceptional biodiversity and protect coastlines, while long-lived deep-sea corals record centuries of ocean history in their skeletons.
WHOI research spans reef ecosystems, deep-sea corals, and the stressors — warming, acidification, and human activity — that threaten them.

Corals are tiny animals with an outsized role — building the vast reefs that shelter much of the sea’s biodiversity in the shallows, and forming slow-growing communities in the cold, dark deep. WHOI studies both, along with the stressors that increasingly threaten them.

Many people think of coral as hard, rock-like formations that attract abundant, diverse marine life. In fact, corals are themselves tiny marine animals called polyps that live together in large colonies.

Coral polyps are relatives of jellyfish and anemones. Some live in shallow water, some in deep; some form hard outer skeletons made of calcium carbonate, others have a soft body encasing hard internal structures known as sclerites. Hundreds of thousands of hard corals with their skeletons glued together form the iconic reef structures that do, indeed, serve as the foundation for important marine ecosystems around the world.

Can multivitamins help save coral reefs?

WHOI scientists are testing "multivitamin" tiles that release trace metals like zinc and manganese to help corals resist heat stress and boost resilience.

How do corals form colonies?

Coral reefs are built by tiny animals called polyps—over 1,000 per square foot—working together to form vast, complex, and vital marine ecosystems.

WHOI’s Amy Apprill "speaks for the reefs" at COP28

A COP28 Moment with WHOI microbial ecologist Amy Apprill.

Digital Reefs: Enabling the Industrial Metaverse with MIT Technology Review

Digital Reefs principal investigator Anne Cohen presented her vision for a technologically supported future of decision-making for coral reefs

Coral reef discovered in the Galápagos Marine Reserve with Alvin

In April 2023, scientists diving in the human-occupied submersible Alvin discovered extensive, ancient deep-sea coral reefs within the Galápagos Marine Reserve.

Boston/New England Regional Emmy® Award Nominations

Watch WHOI's two regional Emmy®-nominated videos: Hope for Corals In Crisis and Give Reefs a Chance!

Hope for Corals in Crisis

Go behind the scenes as WHOI researchers develop cutting-edge tools to detect stressed corals early—before visible damage makes recovery harder.

Give Reefs a Chance

WHOI scientists are racing to save coral reefs with real-time tools, fish sound studies, and robotics to detect stress and disease before it's too late.

Can we use sound to build back reefs?

WHOI scientists study sound as a possible therapy for ailing coral reefs

Ocean Encounters: Giving Reefs a Chance

Coral reefs are vital ocean ecosystems, and they are in trouble. Learn how WHOI scientists and engineers are working to diagnose reefs at risk and bring them back to life.

Listening for home: How corals use sound to build reefs

What does home sound like to you? Scientists investigate how corals use sound to settle and build new reefs

NOAA Live! Saving Corals: A Day in the Life of a Coral Reef Scientist

NOAA Live! Explore a day in the life of a coral reef scientist working to save these vital ecosystems.

Ocean Encounters: Corals in Crisis

A deadly coral disease is spreading fast. Learn how scientists are racing to stop it and save vital reef ecosystems before it's too late.

Inspired to Understand – Amy Apprill

Once landlocked, Amy Apprill now studies coral disease at WHOI, using DNA to uncover clues in reef health and fight a fast-spreading epidemic.

Alvin Makes an Exciting Coral Discovery

Discover a vast deep-sea coral reef off South Carolina, found by Alvin during Deep Search 2018. Watch the 8-hour dive condensed into just 3 minutes.

Deep-water Corals in the Northeast Canyons

Just 100 miles off the most heavily populated coast of North America lie nearly 80 canyons cut into the seabed and continental shelf.

Groundwater: The River No One Sees

Groundwater feeds the ocean in unseen ways—carrying nutrients, pollutants, and clues about environmental change. WHOI scientists use coral to track its flow.

Presentation: Ocean’s Acid Test

Seawater is becoming more acidic due to rising CO2—a serious issue called ocean acidification. WHOI hosts a public event to explain its causes, impacts, and solutions.

Shallow Water Diving

Scuba gives researchers time and access to study reefs, fish, and seafloor up close.

Once and Future Corals

WHOI scientist Conrad Hughen shares insights on studying coral reefs and the challenges they face for the future.

References

Schiller Center for Reef Solutions

Marine Microbiology – Apprill Lab

Fish Ecology Laboratory

Expedition to the Phoenix Islands Protected Area
September 11 to September 26, 2009

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Press releases

July 27, 2026

New WHOI study shows seawater may offer early clues to changing reef health

July 21, 2026

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