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Coral Reef, Seychelles
Photograph by Roberto Schmidt, AFP/Getty Images
Coral reefs are in trouble across the globe as rising greenhouse gas levels warm the oceans and boost the acidity of seawater. Pollution and overfishing make matters worse. Browse this gallery to see photos of healthy and degraded reefs around the world.
Here, waves break over a coral reef off the coast of Mahé, the largest island in the Seychelles. The island nation is made up of some 115 tropical islands in the Indian Ocean.
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Giant Clams, Bolinao
Photograph by Romeo Gacad, AFP/Getty Images
A researcher approaches giant clams off Bolinao in the Philippines. The clams form an integral part of a coral reef's ecosystem. A large clam can weigh more than 440 pounds (200 kilograms) and measure up to 4 feet (1.2 meters) long.
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Sea Urchins, Mediterranean Sea
Photograph by Enric Sala, National Geographic
Sea urchins inhabit a degraded coral reef in the Mediterranean Sea. The sea has lost most of its large fish and red coral to centuries of exploitation.
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Kiritimati Atoll
Photograph by Jennifer E. Smith, Ph.D., Scripps Institution of Oceanography
On Kiritimati (Christmas) Atoll in the central Pacific Ocean, corals have been overgrown by fleshy seaweeds. The cause of this coral to algal phase shift remains unknown.
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Kingman Reef
Photograph by Brian J. Skerry, National Geographic
A school of fish swims over Kingman Reef’s colorful coral. Scientists visiting the remote Pacific Ocean atoll reef describe it as a "time machine," an ecosystem that has survived in an almost pure state of nature.
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Surgeonfish, Palmyra Atoll
Photograph by Randy Olson, National Geographic
Surgeonfish slice through the coral-rich waters of the Palmyra Atoll in the central Pacific Ocean. Some 130 stony coral species grow on Palmyra’s 50 scattered islets, remnants of an extinct volcano.
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Giant Clams, Kingman Reef
Photograph by Enric Sala, National Geographic
A healthy patch reef in a Kingman Reef lagoon includes an abundance of giant clams. Kingman Reef is part of a chain of Pacific atolls and islands (called the Line Islands) that straddles the Equator 1,000 miles (1,609 kilometers) south of Hawaii.
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Gray Reef Sharks, Kingman Reef
Photograph by Brian J. Skerry, National Geographic
Gray reef sharks and red snappers prowl the waters of Kingman Reef for food. Cloudlike schools of fish, a common sight at most reefs, hardly exist here. The healthy abundance of large predators, accounting for 85 percent of the fish biomass, forces most prey fish into hiding.
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Sharks, Southern Line Islands
Photograph by Enric Sala, National Geographic
An abundance of top predator sharks is one sign of a healthy reef, like this one off the southern Line Islands in the Pacific Ocean. Other indications of health include lush and various corals covering the seabed and water as clear as air.
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Red Snappers, Southern Line Islands
Photograph by Enric Sala, National Geographic
Red snappers in the southern Line Islands swim above a pristine coral bed. The remote and rarely visited islands provide a reference point against which to measure change and a blueprint for conservation.
More Ocean Galleries
Ocean Topics
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Acidification
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Ballard, Robert
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Bowermaster, Jon
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Cook-Wise
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De Rothschild, David
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Doubilet, David
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Earle, Sylvia
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Frozen Seafood Benefits
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Goodman, Beverly
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Habitat Destruction
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Invasive Species
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Kristof, Emory
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Marine Food Chain
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Marine Pollution
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Nicklen, Paul
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Norman, Brad
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Ocean Overview
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Overfishing
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Plastiki
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Pristine Seas Expeditions
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Sala, Enric
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Seafood Decision Guide
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Seafood Substitutions
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Sea Level Rise
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Sea Temperature Rise
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Seaver, Barton
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Sustainable Seafood
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Thys, Tierney
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