Coral Reefs of the World -- Unite!

Corals of the World

by
Teia Maman

         
         Dive on an atoll, a coral reef with no pollution, no fishing, no disease. You can see 100 feet through clear water. The coral heads teem with curious fish -- parrots, angels, damsels -- and dauntingly big groupers, snappers and wrasses. Sponges, shrimp, starfish and sea cucumbers, turtles, eels, sharks, turtles, rays, puffer fish, trumpet fish!
           Dozens of species of coral prosper. Turquoise, neon yellow, electric blue corals. Some corals branch, some clump, others grow whorls, flat tables, or mushroom caps. Some are tiny balls, others are giant boulders, and some exist as a mere crust over the hard surface of another. 
         This is an undamaged reef.
         But dive on a damaged reef, in the Philippines, for example, where fishermen catch fish with dynamite, where pollution, sediments and nutrients trickle into the lagoon. The water is cloudy, the coral dead, bleached, disintegrating. There will be few animals, no stunning colors...a dying ecosystem.
         This scenario is unfolding on a planetary scale. Our reefs are endangered, and that is why 2008 has been named "International Year of the Reef." This worldwide campaign aims to increase awareness of the coral reef crisis, and to motivate people to take action to protect this richest of all marine ecosystems.
         Coral reefs are the largest and one of the oldest and most diverse forms of life, living structures that house and feed over a million aquatic species. They evolved over the last 200-300 million years, and are essential to life on earth.
         More than 500 million people around the world depend on coral reefs for food, jobs and recreation. Reefs also come in handy to protect our shores from erosion, hurricanes and destructive waves.
         Coral reefs take up about 300,000 square kilometres of this watery globe, and are the only living structures visible from space. These giant edifices are built by tiny multicellular animals, called polyps. Hundreds to thousands of polyps form colonies, that form coral heads and ultimately entire reefs.
         Polyps reproduce once or twice a year, at the full moon, by releasing egg-sperm clusters into the water. These float to the surface and break up, mix and fertilize. The resulting embryos look like tiny jellyfish, but when settled on the reef, they metamorphose into juvenile polyps, complete with mouth and tentacles, and ready to incorporate their lifelong symbiotic partners -- the zooxanthellae algae, a phytoplankton -- into their tissues. The polyp provides a home, while the algae provides, through photosynthesis, most of the polyp's food, as well as its vivid colors.
         There are two types of coral. "Soft corals" look like feathery plants with a woody core and fleshy rind. They are soft only in appearance, and thrive in warm or cold water, even in the Antarctic, and as deep as 3000 meters.
         "Hard corals," which build the reefs, are not very hardy at all; in fact, they are highly sensitive to environmental changes.
         Natural phenomena like storms, earthquakes, El Nino (regional oceanic warming that alters weather patterns and ocean currents), volcanic eruptions and dust storms can damage reefs. But mostly, we humans damage coral reefs, and at unprecedented rates, due to our burgeoning populations, our industries and activities, and our mismanagement of resources.
         According to a 2004 report, the Status of Coral Reefs of the World, one-fifth of the world's coral reefs are damaged beyond repair. Of the remaining reefs, half are at immediate risk. There are no pristine reefs remaining on earth.
         Coral reefs in the Caribbean have lost eighty percent of their coral species. In the Persian Gulf, about sixty-five percent of the reefs are dead. In South Asia nearly half are dead, and in Southeast Asia, thirty-eight percent are dead.
         Pollution, nutrient-rich water or too much fresh water kills coral species and encourages algae to grow and suffocate reefs, or encourages invasive species, such as the Crown of Thorns starfish, to prey on the coral. Over-fishing for food and for the aquarium trade upsets the delicate ecological balance, and affects even more reefs than pollution, because most reefs are far from sources of pollution. Extensive coastal development and "reclaiming" threatens coral reefs. Another problem is unregulated reef-related tourism, which has expanded.
         Once a reef's health is undermined, it becomes susceptible to bacteria, fungi, and viruses in the water. Coral disease, whose disease mechanisms and transmission are not well-understood, has increased dramatically during the last 10 years.
         But the top threat to the world's reefs is global warming.
         A rise in water temperature of just one or two degrees Celsius can kill the symbiotic zooxanthellae that nourish and give color to corals, and the coral "bleaches out.'' If the water cools, the coral can recover. If not, the coral dies after about ten weeks. Coral bleaching occurs around the globe, and is increasing in frequency and intensity.
         The higher carbon dioxide levels associated with global warming cause the surface waters of the world's oceans to be more acidic. Corals have a harder time producing their calcium carbonate skeletons, and can even dissolve.
         Many groups are now working to conserve the biodiversity, the economic value and beauty of coral reefs. Marine scientists seek to understand, at a global scale, the coral reef crisis, starting with natural baselines, qualitative and quantitative research to estimate and reduce the impact of human activity on species and ecosystems. They search for new ways and improved methods to "grow" reefs and to restore them and their marine species. Many reefs can recover in the space of ten to thirty years, but slow-growing species can take centuries. Scientists and volunteers monitor reefs, using surveys and satellite imagery, run conservation workshops, and teach people about reef protection, ecology and management.
         Several countries have created marine protected areas, such as the Great Barrier Reef in Australia, or the 360,000 km² of reefs and atolls in the Pacific Ocean in American territory north of the Hawaiian Islands. According to a 2007 study, this area is "one of the last remaining intact predator-dominated, large-scale coral reef fish assemblages on earth."
         If we put a stop to fishing methods that kill corals and to land use practices that create sedimentation and nutrient pollution, and if we enforce global policies to reduce ocean warming and acidification, then maybe, just maybe, our great-great-grandchildren will get to dive down among the vivid colors, amazing shapes and feel the pulsing existence of a living, healthy reef.

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