Coral Reefs
The Importance of Coral Reefs
Coral reefs are a precious resource in the ocean because of their beauty and biodiversity. Coral reefs provide shelter for a wide variety of marine life, they provide humans with recreation, they are a valuable source of organisms for potential medicines, they create sand for beaches, and serve as a buffer for shorelines. Coral reefs are built by millions of coral polyps, small colonial animals resembling overturned jellyfish that use excess carbon dioxide in the water from the atmosphere and turn it into limestone.
The Variety of Coral Reefs
Coral reefs can be found in both shallow and deep waters and are classified into 3 categories:
Hard corals
Scleractinia, also called Stony corals, are exclusively marine animals; they are very similar to sea anemones but generate a hard skeleton. They first appeared in the Middle Triassic and replaced tabulate and rugose corals that went extinct at the end of the Permian. Much of the framework of coral reefs is formed by scleractinians. There are two groups of Scleractinia: Colonial corals found in clear, shallow tropical waters; they are the world's primary reef-builders (see below for examples), and solitary corals which are found in all regions of the oceans and do not build reefs. Some live in temperate, polar waters, or below the photic zone down to 6,000 m.
Soft corals
The Alcyonacea, or the soft corals are an order of corals which do not produce calcium carbonate skeletons and so are neither reef-building corals nor do they lay new foundations for future corals. Instead they contain minute, spiney skeletal elements called sclerites. Aside from their scientific utility in species identification, sclerites give these corals some degree of support and give their flesh a spiky, grainy texture that deters predators.
Unlike stony corals, most soft corals thrive in nutrient-rich waters with less light intensity. Almost all utilize zooxanthella as a major energy source. However, most will readily eat any free floating food, such as brine shrimp, out of the water column.
Sea fans
A gorgonian, also known as sea whip or sea fan (soft coral), is an order of sessile colonial cnidarian found throughout the oceans of the world, especially in the tropics and subtropics. Gorgonians are similar to the sea pen, another soft coral. Individual tiny polyps form a colonies that are normally erect, flattened, branching, and reminiscent of a fan. Others may be whiplike, bushy, or even encrusting. A colony can be several feet high and across but only a few inches thick. They may be brightly coloured, often purple, red, or yellow.
In 1999, a deep coral reef 60 m below the surface was discovered by the United States Geological Survey (USGS) Center for Coastal and Wetland Studies near Pulley Ridge, an underwater barrier island west of the Dry Tortugas National Park off the southern coast of Florida. The Pulley Ridge reef absorbs more light by increasing surface area and growing flat rather than the usual vertical growth seen in shallower coral reefs. Other deep water reefs include the Darwin Mounds and the Mingulay reef complex. More is known about shallow water coral reefs in tropical zones than deep-water reefs discovered recently, however much research into these unique ecosystems is being conducted.
Tropical Coral Reefs
Tropical coral reefs are biotic reefs formed in tropical waters by live organisms such as calcareous algae (including red algae) and corals. In contrast, abiotic reefs are formed by the deposit of sand and other materials in shallow water. Organisms responsible for building tropical (biotic) coral reefs can only grow at 20-28°C, so although coral reefs live in all oceans, most are found between the Tropic of Capricorn and the Tropic of Cancer. The best growing habitat for coral reefs is a clear-water photic zone less than 50 m deep where light shines down and microscopic algae can best provide photosynthesis for the corals.
The wide array of coral reef forms includes the Apron reef, the Fringing reef, the Barrier reef, the Patch reef, the Ribbon reef, the Table reef and the Atoll reef. The Apron and Fringe reef both reach down and out from the shore point or peninsula although the Apron reef is typically not as steep as the Fringe reef. Barrier reefs, like the Great Barrier Reef, are separated from the shore by lagoons. An Atoll reef surrounds a lagoon in a circular or uninterrupted fashion and is different from the others because there is no island in the middle.
A Critical Situation
Coral reefs are extremely sensitive to changes in light, temperature (bleaching), overfishing, damaging fishing practices, pollution, and excess sediment from development and erosion. Reefs in Southeast Asia are most at risk of damage due to these factors. Human activity is one of the greatest threats to coral reefs, particularly the destruction of mangrove forests that naturally absorb sediment and nutrients that can suffocate coral reefs with silt and algae blooms.
Former coral reef in the Florida Keys, USA. Destruction most likely due to massive former bleaching events caused by warmer surface waters, nutrient-overload from sewage and overfishing.
Cyanide fishing in the Indonesian and Philippine coral reefs of South Asia stuns and injures valuable fish. Although 85% of the world's aquarium fish are captured with this destructive method, they suffer a 90% mortality rate usually several weeks after they have been poisoned by cyanide. Fishermen in developing countries depend on reef fish for income to provide for their families; however, illegal fishing practices and overfishing is depleting fish stocks in these areas, rapidly threatening the livelihood of these local populations. Fishermen hit the coral reefs with crowbars to shake out stunned fish and they also even fish with dynamite, which often destroys every living thing on the reef. Many reefs once teeming with life are now wastelands that even the most vigorous conservation efforts can't begin to restore.
With approximately 85,470 sq km of tropical coral reefs, Indonesia hosts about 33% of the total coral in the world and 25% of all fish species. However, in 2000 it was reported that over 70% of the coral reefs are in bad to fair condition due to fishing practices, out of control tourism, and long periods of bleaching. Coral reefs in the Philippines were found to be 77% less productive from 1966-1986, while the national population doubled in size. If the destruction continues, we will lose about 70% of the world's reefs within 25-40 years.
The effects of El Niño during 1998 and 2004 are an example of the natural factors that influence the growth of coral reefs. During this El Niño, sea temperatures rose and many coral reefs were bleached or obliterated. Coral bleaching occurs when the single-celled algae vital for coral reef survival and known as symbiotic zooxanthellae are rejected from the coral, soft corals, some sponges and even Tridacna clams. The pigment containing organisms are lost as temperature or stress level due to increased light reaches intolerable levels. As temperatures return to normal, some reefs can recover within several weeks or months. However, equilibrium may not be restored due to global warming and the bleaching effect exposes corals to white and black band diseases. There is some evidence that global warming may actually add to the productivity of an ecosystem through an increase in carbon dioxide and higher temperatures, though the validity of this evidence remains to be seen.
Massive coral bleaching occurred in the Great Barrier Reef of Australia between 1998 and 2002 and in reefs in the Indian Ocean, the Maldives, Sri Lanka, Kenya, Tanzania, and the Seychelles. Most areas in the Great Barrier Reef rebounded with little damage but in some areas approximately 90% of the coral has vanished. The reefs in the Indian Ocean suffered the most damage and 90% of the coral reefs were lost in the remaining five locations. In Indonesia, the damage is less extensive but more diversity is lost in an area significantly more difficult to restore.
Conservation and Restoration
Part of the problem with the coral reefs in Indonesia was the move made in 1991 to delocalize power in the Indonesian and Philippine governments. The result was a lack of funding and national support for protection of the South Asian reefs. More recently, conservation efforts have included roping off Marine Protected Areas (MPAs), research and implementation of electrolysis as stimulant for growth, moving reefs to new places and cutting back on harmful fishing practices—all expensive and time consuming endeavors estimated to cost over $100 million dollars. MPAs have been established in regions like Indonesia so that sustainable fisheries can be managed and ecologically important habitats will be protected with a social and biological objective. Laws similar to those found in national parks have been developed to prohibit illegal harvesting of fishes. The hope is that by designating MPAs, coral reefs will be restored, areas will become more beautiful, diversity of life will not be lost and communities will have a sustainable source of income in fishing and tourism. Work is being done to effectively manage MPAs and scientists have found that co-management, the collaboration of local, provincial and national parties, is an effective management strategy. As with many organizations, MPAs will have to overcome challenges that include finding participants, streamlining viewpoints about how effective certain ideas will be and raising enough money to implement change.
An international and non-profit organization called the Marine Aquarium Council or MAC was created to make the aquarium fish trade more responsible and sustainable through education and to limit harmful fishing practices. By avoiding stock depletion, adding more governmental regulation of reefs, managing reefs better, learning how to take care of fish and food once it is caught and creating a reliable data record, the MAC hopes to avoid a ban on the aquarium industry with a loss of income to the locals and a boom in illegal fishing. Among those involved in the project are researchers, conservationists and industry operators, all who would like to find a sustainable way to meet industry demands through education in the form of international standards and certification plans. MAC hopes that consumers, collectors and retailers will begin to realize how important it is to them and others to sustain their most valuable natural resource—the coral reef.
Other conservation efforts by various organizations include the intricate process of growing coral and coral reefs, a fragile organism that is sensitive to any environmental or biological change. Coral can be grown using a process known as mineral accretion where limestone is stimulated to collect on metal by a safe low voltage current, providing a nice place for baby coral to latch on and grow. The voltage itself can be provided using solar panels or energy from wave action. Scientists active in the Global Coral Reef Alliance (GCRA) grow coral reefs and will even show others the technique. To learn more and view pictures of the restoration effort visit http://www.globalcoral.org.
Center for Biological Diversity: Staghorn corals
Center for Biological Diversity: Elkhorn corals
» Coral Reef Conservation groups
» Marine Aquarium Council
» Wikipedia.org: Global warming
» Global Coral Reef Alliance
Coral Reef News
'Globetrotting' new worms discovered on Great Barrier Reef and Swedish coast
Between the grains of sand on the sea floor there is an unknown and unexplored world. Scientists have just found new animal species on the Great Barrier Reef, in New Caledonia, and in the sea off the Gullmarsfjord in the Swedish county of Bohuslan.
Participation important for healthy marine parks
The involvement of locals is a key ingredient in the success of marine parks which protect coral reefs and fish stocks. The largest-scale study to date of how coastal communities influence successful outcomes in marine reserves has found that human population pressure was a critical factor in whether or not a reserve succeeded in protecting marine resources -- but so too was local involvement in research and management.
Ancient corals hold new hope for reefs
Fossil corals, up to half a million years old, are providing fresh hope that coral reefs may be able to withstand the huge stresses imposed on them by today's human activity. Reef ecosystems were able to persist through massive environmental changes imposed by sharply falling sea levels during previous ice ages, an international scientific team has found. This provides new hope for their capacity to endure the increasing human impacts forecast for the 21st century.
Climate change and coral reefs: Coral species has developed the 'skills' to cope with rising temperatures
Marine reserves are increasingly important for species that are being forced by climate change to move to a new home, adapt to new conditions or die. Biologists have now compared the relative benefits of large and small protected areas in perpetuating populations. Interestingly they have also found a coral species that has developed the "skills" to cope with rising temperatures.
World-class protection boosts Australia's Great Barrier Reef
Australia's Great Barrier Reef is showing an extraordinary range of benefits from the network of protected marine reserves introduced there five years ago, according to a comprehensive new study published.
Will coral reefs disappear?
How vulnerable are coral reefs to climate change due to higher ocean temperatures?
Diversity of corals, algae in warm Indian Ocean suggests resilience to future global warming
Corals that harbor unusual species of symbiotic algae have been discovered thriving in water that is too warm for most other corals. The discovery gives hope that coral reefs and the ecosystems they support may persist -- at least in some places -- in the face of global warming.
Marine reserves in the spotlight: Meeting both conservation and fisheries goals
Marine reserves are known to be effective conservation tools when they are placed and designed properly. This week, a special issue of the Proceedings of the National Academy of Sciences is dedicated to the latest science on marine reserves, with a focus on where and how reserves can most effectively help to meet both conservation and fisheries goals.
Coral can recover from climate change damage, new research suggests
A new study by scientists in the UK provides the first evidence that coral reefs can recover from the devastating effects of climate change. The research shows for the first time that coral reefs located in marine reserves can recover from the impacts of global warming.
Indian Ocean climate event recurs quicker with global warming
The Indian Ocean Dipole (IOD), an oscillation of sea surface temperatures in the Indian Ocean, has become a major influence on the weather variations in the Indian Ocean region. During positive IOD events, abnormally warm sea surface temperatures in the western Indian Ocean are accompanied by severe droughts over the Indonesian region and heavy rainfall over east Africa.
Fish with attitude: Some like it hot
Coral reef fish can undergo a personality change in warmer water, according to an intriguing new study suggesting that climate change may make some species more aggressive.
Discovery of the Jekyll-and-Hyde factors in 'coral bleaching'
Scientists are reporting the first identification of substances involved in the Jekyll-and-Hyde transformation that changes harmless marine bacteria into killers that cause "coral bleaching."
Marine life collected to inventory DNA sequence of all Pacific island's living species
Researchers are collecting marine invertebrates on the French Polynesian island of Moorea as part of a massive effort to inventory the DNA sequence of every living species there.
Sponges recycle carbon to give life to coral reefs
Coral reefs live in some of the most nutrient deficient waters on the planet, so how do they survive? Marine biologists have discovered that certain sponges could be the key to reef survival. They recycle dissolved organic carbon that is unavailable to other reef residents.
Coral Reefs Inspire Rare Consensus -- Just Save Them
One of the first set of studies to examine what tourists and recreation enthusiasts actually think about coral reef ecosystems suggests they are a rare exception to controversies over human use versus environmental conservation -- their stunning beauty is so extraordinary that almost everyone wants them protected in perpetuity.
Calm Before The Spawn: Climate Change And Coral Spawning
Biologists have explained why corals spawn for just a few nights in some places but elsewhere string out their love life over many months. A new study shows that corals spawn when regional wind fields are light. When it is calm, the eggs and sperm have the chance to unite before they are dispersed.
Marine Lab Team Seeks To Understand Coral Bleaching
With technology similar to that used by physicians to perform magnetic resonance imaging scans, researchers are studying the metabolic activity of a pathogen shown to cause coral bleaching, a serious threat to undersea reef ecosystems worldwide.
Flower Garden Banks National Marine Sanctuary Among Healthiest Coral Reefs In Gulf Of Mexico
Flower Garden Banks National Marine Sanctuary is among the healthiest coral reef ecosystems in the tropical Caribbean and Gulf of Mexico, according to NOAA researchers. Their report offers insights into the coral and fish communities within the sanctuary based on data collected in 2006 and 2007.
Coral Bleaching Increases Chances Of Coral Disease
Mass coral bleaching has devastated coral colonies around the world for almost three decades. Now scientists have found that bleaching can make corals more susceptible to disease and, in turn, coral disease can exacerbate the negative effects of bleaching. A new article shows that when they occur together, this combination of afflictions causes greater harm to corals than either does on its own.
Ocean Acidification: Impact On Key Organisms Of Oceanic Fauna May Be Worse Than Predicted
In addition to global warming, carbon dioxide emissions cause another, less well-known but equally serious and worrying phenomenon: ocean acidification. Researchers have just demonstrated that key marine organisms, such as deep-water corals and pteropods (shelled pelagic mollusks) will be profoundly affected by this phenomenon during the years to come.
