Coral reef

From Academic Kids

Some of the  of a coral reef.
Some of the biodiversity of a coral reef.

Coral animals come in three varieties: hard, soft and sea fans. Coral reefs take two main forms: shallow water reefs and deep water reefs. Deep water reefs have only recently been discovered, often located in dark, cold water and growing very slowly in the absence of light. The rest of this article is concerned with the hard corals that build shallow water tropical reefs.

A coral reef is a type of biotic reef developing in tropical waters. Although corals are major contributors to the overall framework and bulk material comprising a coral reef, the organisms most responsible for reef growth against the constant assault by ocean waves are calcareous algae, especially, although not entirely, species of red algae.

Water temperature of 20-28 ?C (68-82 ?F) is needed for growth of the coral reef. Coral reefs are found in all oceans of the world, generally between the Tropic of Cancer and the Tropic of Capricorn, because reef-building corals live in these waters. Reef-building corals are found mainly in the photic zone (<50m), where the sunlight reaches the ground and offers the corals enough energy. The corals themselves do not photosynthesise, but they live in a symbiotic relationship with types of microscopic algae that photosynthesise for them. Because of this, coral reefs also grow much faster in clear water, which absorbs less light.

Such reefs take a variety of forms, defined as follows:

  • Apron reef — short reef resembling a fringing reef, but more sloped; extending out and downward from a point or peninsular shore.
  • Fringing reef — reef extending directly out from a shoreline, and more or less following the trend of the shore.
  • Barrier reef — reef separated from a mainland or island shore by a lagoon; see Great Barrier Reef.
  • Patch reef — an isolated, often circular reef, usually within a lagoon or embayment.
  • Ribbon reef — long, narrow, somewhat winding reef, usually associated with an atoll lagoon.
  • Table reef — isolated reef, approaching an atoll type, but without a lagoon.
  • Atoll reef — a more or less circular or continuous barrier reef surrounding a lagoon without a central island; see atoll.


The Importance of Coral reefs

Image provided by Classroom Clipart (
Image provided by Classroom Clipart (
Coral reefs provide a natural habitat and massive protection for different species of fish. They are not plants; they are living organisms that provide an environment for fishes to breed. Without them, fishes in the ocean are homeless. According to one professor, corals are colonial organisms that need to be exposed to sun, in order for them to grow. The corals also influence the amount of carbon dioxide in the ocean, because coral polyps, which are tiny invertebrates (cnideria) that look like upside-down jellyfish, fix carbon dioxide to form limestone. This is a major process that acts as a 'carbon sink' for excess carbon dioxide in the atmosphere, as well as maintaining an environment of exceptionally high biodiversity despite relatively poor nutrient availability.


In December 2004, United States Geological Survey (USGS) researchers announced the confirmation of the discovery of the deepest coral reef ever found in the United States. The reef is in the Pulley Ridge area, a north-south-trending drowned barrier island, more than 60 miles (100 km) long, approximately 40 miles (70 km) west of Dry Tortugas National Park. It is up to three miles wide and about 20 miles long (5 km wide and 30 km long), and located at a depth that ranges from 200 to 250 feet (60 to 80 m). Unlike most coral reefs, which tend to grow vertically, Pulley Ridge coral grows flat, an adaptation to the limited penetration of light at that depth to increase surface area exposed to sunlight.

Similar deep reefs occur in other parts of the world, e.g. the Mingulay reef complex and the Darwin Mounds located off the west of Scotland in about 150 metres of water.

Threats to Reefs

Bioerosion (coral damage) such as this may be caused by . [1] (
Bioerosion (coral damage) such as this may be caused by coral bleaching. [1] (

Humans continue to represent the single biggest threat to coral reefs. In particular, land-based pollution and over-fishing are the most serious threats to these ecosystems. The live food fish trade has been implicated as one driver of decline due to the use of cyanide in the capture of fish.

High levels of land development have also been threatening the survival of coral reefs. Within the last 20 years, the once thick mangrove forests, which absorb massive amounts of nutrients from runoff caused by farming and the construction of roads, buildings, ports, channels, and harbors, are being destroyed. Nutrient-rich water causes algae to thrive in coastal areas in suffocating amounts, also known as algal blooms (Sadovy, Y.J.).

Due to the increased demand for live reef fish in North America and Europe, the use of cyanide fishing has increased in the Indo- Pacific region. 85% of the of the world?s aquarium fish are caught in this region and almost all of them are caught using cyanide. Cyanide is used to stun the fish, in order to easily capture them for trade. It is detrimental to the organs of fish, which would explain the 90% mortality rate of cyanide captured fish. Cyanide is also very destructive to the surrounding coral reef ecosystems. It kills corals and other reef invertebrates. (Barber and Pratt, 1-2) Corals are also harmed by the poor harvesting practices of the live fish trade. Fishermen sometimes pound on the reef with crowbars and rocks to scare fish into nets or pry corals apart to retrieve stunned fish. (Butler, 1)

A major catalyst of cyanide fishing is poverty within fishing communities. In areas like the Philippines where cyanide is regularly used to catch live aquarium fish, the percentage of the population below the poverty line is 40%[2] ( In such developing countries, a fisherman might resort to such unethical practices in order to prevent his or her family from starving.

Dynamite fishing is another extremely destructive method that fishermen use to harvest small fish. The procedure of dynamite fishing starts with a bottle that is filled with explosives made of potassium nitrate, once the dynamite goes off the explosion brings about an underwater shockwave causing the swim bladders of fish to burst making them float to the top. A second blast is often set off after the first to kill any larger predators that are attracted to the initial kill of the smaller fish. This method of fishing does not only kill small fish but also claims the lives of many reef animals that are not edible or wanted, such as the coral itself. Areas that used to be full of coral now are like desert sand, no sign of coral or any other reef animals that used to inhabit it.

During the 1998 and 2004 [[El Ni񯝝 weather phenomenons, in which sea surface temperatures rose well above normal, many tropical coral reefs were bleached or killed. Some recovery has been noted in more remote locations, but global warming could negate some of this recovery in the future. However, Ben McNeil of the University of New South Wales hypothesises that reefs are not in decline, and may exceed pre-industrial levels by as much as 35 percent by 2100, especially because of the positive influence of global warming. However, growth in some reefs due to global warming is expected to be offset by declines in other reefs, due to the comfortable temperature range for a coral being close to the temperature at which they bleach.

In general, Southeast Asia coral reefs are at risk from damaging fishing practices (such as cyanide and blast fishing), overfishing, sedimentation, and bleaching. A variety of activities, including education, regulation, and the establishment of marine protected areas, are underway to protect these reefs.Indonesia has nearly 33,000 square miles of coral reefs. Its waters are home to a third of the world?s total corals and a quarter of its fish species. Coral reefs of Indonesia are located in the heart of the Coral Triangle and have been victim to destructive fishing, unregulated tourism, and bleaching do to climatic changes. Many of the diverse coral reefs are being smothered by sediment and poisoned from cyanide fishing and organic pollution. Data from 414 reef monitoring stations throughout Indonesia in 2000 found that only 6 percent of Indonesia?s coral reefs are in excellent condition, 24 percent are in good condition, and approximately 70 percent are in poor to fair condition (2003 The Johns Hopkins University). According to The Nature Conservancy organization, if the destruction increases at the current rate, 70% of the world?s coral reefs will have disappeared within our life times

Protection and Restoration of Reefs

The coral reefs of the Indonesian islands are the most diverse in the world as well as one of the most difficult natural phenomenons to restore. In 1991 Indonesian and Philippine governments made a move to decentralize the capacities of enforcement authorities with regards to coastal management. This led to a lack of national support and funding and a great challenge for smaller sectors in facing the destruction of Southeast Asian coral reefs (Courtney 42). Though in 2002, 18% of the regions reefs were officially destroyed and 85% were called threatened, efforts for restoration are becoming more evident. Some of these efforts include creating isolated marine sanctuaries, transplantation of reefs, forms of electrolysis to advance growth and restrictions on harmful fishing techniques. Along with being labor intensive and hard to enforce, these efforts are extremely expensive; the US is estimated to spend $100 million or more(Fox 2).

An ill-balanced economic concept has occured in Indonesian and Philippine waters with coral reefs. A predicted net benefit of coral reef fisheries is 2.4 US billion a year (Sadovy) throughout Southeast Asian locations, while poverty levels are at an extreme high. As outside sources provide supplies for illegal coral/fish harvesting, rural fishermen decline to these methods in order to simply battle against starvation. The cycle of destruction becomes perpetual.

The concept of Marine Protected Areas (MPAs) has been introduced in these regions and elsewhere in attempt to promote responsible fishery management and habitat protection (Gjertsen). Much like the designation of national parks and wild life refuges, potentially damaging extraction activities are prohibited. The objectives of MPAs are both social and biological. Some of these include restoration of coral reefs, aesthetic maintenance, increased and protected biodiversity, and economic benefits. Conflicts surrounding MPAs involve lack of participation, clashing views and perceptions of effectiveness, and funding (Christie).

It is estimated that about 60% of the world?s reefs are at risk due to destructive, human-related activities. The threat to the health of reefs is particularly strong in Southeast Asia, where an enormous 80% of reefs are considered endangered. One method of coastal reef management that has become increasingly prominent is the implementation of marine protected areas (MPAs). Indonesia currently has nine MPAs, claiming a total 41,129 squared kilometers of coastal are to be under protection. A study done on one of the more recently established MPAs in Indonesia showed the need for co-management when it comes to the success of managing MPAs. This collaborative approach emphasizes the cooperation and partnership between parties at the national, provincial, and local community level. (Clifton 389-395)

The coral reefs in the Philippines and Indonesia are disappearing rapidly due to dynamite and cyanide fishing. Between 1966 and 1986 the productivity of coral reefs in the Philippines dropped by one-third as the national population doubled (State of the Reefs). In Indonesia as well, over eighty percent of the coral reefs are under threat (The Jakarta Post). These two locations are home to the world's most diverse range of corals. If the rate of destruction does not diminish, seventy percent of all the world's coral reefs will be gone in the next twenty-five to fourty years (the Philippines). Fortunately, efforts, such as Marine Protected Areas, are being made to promote coral reef restoration.

The Marine Aquarium Council (MAC), an international, not-for-profit organization that works to bring responsibility and sustainability to the aquarium fish trade industry, is also concerned with very specific human practices that bring harm and destruction to the coral reefs. Such concerns include the use of cyanide to stun and collect the fish, poor handling and husbandry practices, stock depletion, limited government regulation and reef management and lack of reliable data about the industry. A ban on the aquarium industry would create a loss of income to communities, as well as an increase in the illegal trade industry. MAC encompasses a large network of researchers, industry operators and conservationists to ensure objective solutions that can benefit the industry and the environment. Hughes, et al, acknowledges that ?with increased human population and improved storage and transport systems, the scale of human impacts on reefs has grown exponentially. For example, markets for fishes and other natural resources have become global, supplying demand for reef resources far removed from their tropical sources? (Science 2003). MAC believes that there is a sustainable and responsible way to meet the demands of the industry by creating international standards and certification schemes to inform and educate consumers, collectors and retailers on the importance of sustaining healthy coral reef habitats. For more information, see MAC's website:


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