Coral Reefs: Learn All About These Underwater Structures

In our today’s article we will refer to Coral Reefs, Marine’s wonderful structures that serve as home to thousands of species, but which are currently in serious danger. Join us in this story of what is coral.

Coral Reefs

What are Corals Reefs ?

Coral Reefs: Coral reefs are  underwater structures  caused –- by the calcium carbonate-secreted   by  themselves.

It’s a kind of biotic  reef, formed by colonies of stony corals  which generally live in marine waters of Scarce nutrients.

These stony corals are marine animals made up of polyps, gathered in different ways, depending on the species, very similar to sea anemones, which are related.

But contrary to sea anemones, coral polyps of the Scleractinia order, produce carbonate exoskeletons, which provide support and protection to their bodies.

It is known that these coral reefs are better developed in warm, not so deep, crystal clear, sunny and inner agitated waters.

 Here we bring you a video example of how reefs are formed. Also I recommend…

Biodiversity of Coral Reefs:

 Coral reefs, are usually called «rainforests of the sea», since they make up one of the planet’s most diverse ecosystems.

In spite  they occupy less than 0.1% of the total extent of the oceans, only equivalent to half of the surface of France, they are the habitat of a quarter (1/4) of all marine species, which includes fish,

Mollusks, worms, and crustaceans echinoderms, sponges, tunicates, and more.

Due to its strategic location between the beach and the open sea, coral reefs function as protective barrier to the mangroves and the meadows of sea grass, protecting them from the pounding of the waves.

Watching   the movement of fishes  around coral reefs,   represents a wonderful view for  anyone who can approach, their  bright and beautiful colors, are a fantastic proof of the goodness of God in their  creation.

In compensation, these mangrove and sea grass protect the coral reefs of the sedimentation… but they also function as reproduction and breeding areas for many of the species that make up  the ecosystem of coral reefs.


Economic importance of marine coral:

Coral reefs also have a great economic importance, and it is that they provide ecosystem services for tourism, fishing and the protection of the coasts.

The total annual economic value of coral reefs is estimated at 375 thousand millions of dollars. But reefs are very fragile ecosystems, since they are very sensitive to changes in water temperature.

In this sense, the Global Fund for Nature Estimates, that the economic cost of the disappearance of a kilometer of coral reef would be between US $137,000 and US $1,200,000, what would happen in a span (of 25 years. )

The incidence is so, since more than six million tons of fish are taken from coral reefs annually.

And it is that coral reefs properly managed, present an annual average yield that is around 15 tons of seafood per each square kilometer. By way of example, only in Southeast Asia, maritime products in coral reef fishing generates about $2.4 billion a year.


However to optimize the management of coastal coral reefs, World Resources Institute (WRI) designed tools, in partnership with 5 Caribbean counties, to calculate both, the value of tourism and  the protection of the coast and fishing, related to these reefs

In  April 2011 working papers  were  published ,covering Santa Lucía, Tobago, Belice and the Dominican Republic.  A  document about  Jamaica  was in  development  stage.

The  purpose  of the WRI was  to ensure,  that the results of the study,  support better coastal policies, as well as the planning of the management of the zone.

In the study  related to Belize, the value of the services of the reefs and mangroves  was  calculated in a staggering  amount between $395 and 559 million per year.



Unfortunately coral reefs are dying around the world. The main threats to these extraordinary ecosystems are the extraction of coral as well as agricultural and urban runoff, pollution, organic and inorganic; overfishing, fishing with explosives and the diseases of corals. The excavation for channels of access to Islands and bays, is also added to these threats


However the biggest threats include the increase of the temperature of the sea,  as well as the elevation of the sea level and the change of pH, as a result of acidification of the oceans, all these factors are  associated with greenhouse gases emissions.

Coral Bleaching:

Some reports about  the effects of El Niño, have shown that coral bleaching has reached its highest level since 1998, when the consequences of the  climatic phenomenon resulted in the deaths of 16% of the coral reefs on the planet,  due to the increase of the water temperature.

But in the province of Aceh, in Indonesia, for example, a mortality rate of 80% bleached corals was  reported.

In spite the gravity of the matter,  scientists  do not understand the long term impact  of coral bleaching, but  they  know that it makes them vulnerable to various diseases, which also stops its development and affects their reproduction. Severe bleaching causes massive  death.

In July 2010, Malaysia was forced to close several dive sites, where virtually all the corals were damaged by bleaching.

In order to find answers to these global ills, scientists study the different factors that have an impact on coral reefs.


Among these factors, in addition to others already mentioned in this article, we find  the role of the Ocean as a sink for carbon, ultraviolet light, different viruses, the impact of dust storms carrying pollutants to distant reefs and bloom of algae.

Serious global estimates  suggest that about 10% of coral reefs are already dead. But as if this out shortly ,  around 60% of the total of coral reefs is at risk as a result of the destructive activities of humans .

Although the Outlook is particularly troubling for Southeast Asian marine coral, where 80% of these are considered in danger of extinction.

If   current conditions persist, it  is estimated that in the Decade of 2030, 90% of reefs will be  at risk due to human activities and climate change, and in the decade  2050 the situation will reach all the coral reefs on the planet.

Recent studies demonstrated that eco-tourism at  the Great Barrier Reef, is  contributing to increase the diseases  that cause damages to this structure. .

In 2013, a group of international experts said in a study that the coral reefs of the Caribbean have ceased to develop, or worse yet, have begun a process of erosion by the low amount of carbonate, which has declined by 70%.

The study also showed that many Caribbean reefs, have a precarious balance, being very poor and low-complexity compared to the Great Barrier Reef. The research was held in Bahamas, Bonaire and Belize, as well as the Grand Cayman Island, being published in the journal Nature Communications, which is financed by the British Fund Leverhulme Trust.

Now let’s see how the process of coral bleaching is generated..

Protective Measures

The marine protected areas (MPAs) have taken a great importance for the management of the coral reefs in recent years. These AMP’s encourage responsible management of fisheries and habitat management.

Just like the national parks and wildlife refuges, the AMP’s prevent potentially harmful activities. They also incorporate social and biological objectives, such as reef restoration, aesthetics, biodiversity and economic benefits.

On the other hand, in order to halt and reverse the acidification of the oceans, different laws have been  promoted , to reduce the greenhouse  gases emissions, such as carbon dioxide.

In the United States. , the «Clean Water Law» puts pressure to government agencies to control and limit the runoff of contaminants which can lead to acidification of the ocean.


In addition, preventions of overload of storm water, as well as buffer between agricultural land zones and the coast area have been installed. It is a law also promotes the protection of delicate ecosystems of river basins such as wetlands.

The Clean Water Law is a project sponsored by the Federal Government, which is overseen by several organizations..

In Australia, the Great Barrier reef is protected by the authority of the Great Barrier Reef Marine Park. It’s a legislative structure, which includes a well detailed action plan.

This plan consists of various management and awareness of visitors strategies, but also pursues carbon emission reduction in order to reduce acidification of the oceans to prevent polluted coral reefs.

Let´s see this beauty of Costa Rica:

Formation of  Coral reefs

Most  Coral reefs were formed after the last glacial period, when ice´s melting  caused the rise in the level of the seas and the consequent flooding of continental shelves.


This means that in general terms,  coral reefs are less than 10 thousand years old. Thus, when coral communities settled in the continental shelves, these reefs grew vertically, engaged to the rise of the water level.

But coralline  reefs characterized  by a  very slow development, became drowned reefs surrounded by too much water, thus they couldn´t receive enough light to survive.

Origin of the Great Barrier of Coral

The Great Barrier of Coral, formed  around 20 thousand years ago, is a clear example of how coral reefs grew in the continental shelves.

In that time, the sea level was 120 meters lower than at present. And since the sea level rose, both water and corals invaded what were formerly hills of Plains on the coast of Australia.

But 13 thousand years ago, the sea level had elevated 60 meters below the level that currently has. By then many hills of the continental coastal plain had already become Islands.


Later, with the steady rising  of the sea level, water surpassed the peaks of almost all of these continental islands , allowing corals  to   cover the hills, forming the present cays and coral reefs.

During the last 6 thousand years, the  level of the sea of the Great Barrier Reef has not varied significantly, while the age of the living structure of  modern reefs, is estimated  in  6 thousand to 8 thousand years.

The colossal structure of  the Australian Great Barrier Reef, represents the largest of its kind in the world, stretching for 2 thousand  km ,and  separated from the coast  for   a distance between 300 and 1,000 meters.  The Australian Great Barrier of Coral can be observed from the space, due to its height .


When they are healthy, tropical coral reefs grow horizontally at a rate of 1 to 3 cm per year, and between 1 and 25 cm vertically, each year. However, they are unable to grow above sea level.

In addition, hermatypic corals cannot grow in depths greater than 150 m, because they require sunlight.


Types of coral reefs

Coral reefs are the most extensive, and they also contain the biggest quantity and diversity of underwater wildlife.  They are usually very colorful, which attracts many tourists who enjoy the underwater scenery.

Other types of coral reefs:

Coastal  Reef:  is the one that connects directly to a coastal shore or is separated from it by a channel or shallow lagoon.

Barrier Reef: it is a reef  separated from the mainland coast or an island, by a canal or deep lagoon.

Atoll  Reef: is a more or less a  circular barrier reef, located around a lagoon without a central island

Patch Reef: represents a low concentration of coral reef, usually within a lagoon or inlet often in a circular way  and fringed by sand or sea grass.  Patch reefs are very common.

Inclined  Coastal Reef: is quite similar to a coastal  reef but more inclined. It stretches out and down from somewhere or peninsular coast.


Bank Reef:  It has a linear or semi-circular form. It is bigger than a patch reef.

Ribbon Reef: it is a long and low-bandwidth reef, which may be winding, and usually attached to a lagoon of atoll.

Table Reef: It is  isolated, resembling the atoll type, but without a lagoon.

 Habili (from the Arabic «not born»): this is a type of reef of the Red Sea, arriving not long enough to the surface to generate a visible wave, but for this reason may represent a hazard to ships.

Micro Atolls: Some species of corals form communities called micro atolones ( like small atolls ),  its vertical growth is  limited by the mid-tide level

Submarine Mount or  Guyot: this case occurs when a coral reef cannot develop  enough to reverse the collapse of a volcanic island. Thus a seamount, also called guyot is formed. The upper part of the guyots is flat, due to the effects of erosion by waves and wind.

Origin of the color of coral reefs

Coral reefs sustain different symbiotic relationships. But among them, zooxanthellae in particular, provide energy to the coral in the form of glucose, amino acids and glycerol. Coming to provide up to 90% of the energy requirements of corals.

On the other hand, as an example of mutualism, coral provide protection to the zooxanthellae, found in an average of 1 million per each cm3 of coral, representing in addition a constant supply  of carbon dioxide,  that zooxanthellae    requires for photosynthesis.

This Mutualism causes   the color of coral reefs. The color of corals depends on the combination of shades of Brown that provide the zooxanthellae, as well as pigmented proteins, causing the tones of red, blue and green, among others, produced by themselves.


But corals also absorb nutrients, including inorganic nitrogen and phosphorus, taken directly. from the water.

The coral that loses much of the zooxanthellae, as consequence of an  increase in the temperature of the water, to cite a cause, becomes white, or  pastel-colored, especially those  corals that are widely pigmented with their own proteins of colors.

This fact is known as bleaching and represents a serious condition which, if it is not remedied, may destroy the coral.

Major coral reefs of the world

Coral reefs cover an area of approximately 284.300 km2, which is slightly less than 0.1% of the total surface of the oceans.

The Indo-Pacific region, including the Red Sea, the Indic Ocean, Southeast Asia and the Pacific, is 91.9% of this total.

Southeast Asia covers 32.3%, while the Pacific, including Australia, 40.8 percent. Thus, coral reefs in the Atlantic and the Caribbean region represent just 7.6% of the total.

The Great Barrier of Coral:


The Great Barrier of Coral: , Composed of over 2,900 individual reefs and 900 Islands, stretches for more than 2300 km off the coast of Queensland, Australia.

It is the largest reef on the planet and perfectly visible from the moon. To get an idea of its size, its surface is superior to all the British Isles.

The diversity of life that brings this formidable coral complex is unimaginable. While its color, beauty and variety of forms, they can hardly be overcome.

For this reason, since 1981 is considered Heritage of Mankind and, in consequence, duly protected so that its  fragile balance is not affected by the action of man.

This structure is constituted by a regime of about 3,000 individual reefs and 900 islands of coral, separated by narrow channels, just below the surface of the Coral Sea.

But this reef is as diverse as a rainforest, serving as home to thousands of marine animals, including sharks, barracudas, turtles and more 1,500 different species of tropical fish.


This monumental natural structure, which extends for more than 2 thousand kilometers on the northeast coast of Australia, brings 5,4 thousand million dollars per year to the economy of its country, either through fishing or as an area of recreation and tourism.

This region which is protected by  UNESCO, begins at the Sandy Island, about 300 kilometers  above Brisbane, the capital of Queensland, to New Guinea.


Unfortunately, according to a recent study, the Great Barrier Reef has lost more than half of its structure in the last 27 years, as a result of the storms, the pillaging that practice the  sea stars  and bleaching  caused by climate change.

Even  worse, reefs could remain  deteriorating  in the same way until 2022, if the appropriate corrective means are not taken , report   scientists at the Institute of Marine Sciences and the University of Wollongong, in New South Wales State.

The disappearance of half of the original coral coverage, represents a source of great concern, since it is synonymous of the loss of habitat for tens of thousands of marine species, estimated experts, who have developed 2,258 scientific studies in the last 30 years about the problem.


It is known that tropical cyclones of great intensity, of which 34 are counted since 1985, have been responsible for 48% of the Great Barrier Reef degradation; followed by a species of starfish, the  invasive Acanthaster Planci , popularly known as «Crown of thorns», that feeds on algae, which accounting for 42% of the responsibility in this case.

In this sense , two serious episodes of bleaching occurred in 1998 and 2002. , both of them  related to the increase of the temperature of the oceans, with a terrible impact of great importance, particularly in the Central and Northern sections of the Reef.

However, one of the authors of the study, Hugh Sweatman, holds that the barrier has the capability  to reconstitute itself

Protective Measures

 But fortunately now this large reef, is  the largest network of marine strictly protected areas of the planet, since the implementation of a new conservation plan, after 4 years of campaigning by the Worldwide Fund for Nature.

Under this program, the protected area of the reef system will grow from 4.6% to 33% of the Marine Park and World Heritage Area currently, area spanning more than 11 million hectares

In this region, fishing  will be prohibited , well either for commercial or sports purposes despite the fact that it will be available to tourism.

This novel program of conservation is very significant because only 0.5 per cent of the seas and oceans are protected at present, compared with 12% of the Earth’s surface. opposing that coral reefs, in particular, are threatened by climate change, overfishing, as well as by the pollution of the coast.

Experts expect that this strict protection of the great barrier reef encourage other countries to follow the Australian example in vital sea areas,  for example the sea Sulu-Sulawesi, in Southeast Asia, as well as the Mesoamerican Reef, in Central  America,  or the  Mediterranean.

Here’s an alarming video about the great Coral barrier, Australia


Other importants reefs

The Mesoamerican Reef, extends about 1 thousand km along the coast of the Caribbean Sea, from the Isla Contoy, in the Yucatan Peninsula, culminating in the Bay Islands in Honduras.

    • The lagoons of New Caledonia are the second largest double coral reef, in the world reaching a length of 1500 km.
    • While the barrier reef of Andros, the third largest, is located following the East coast of the island of Andros, between Andros and Nassau.
    • The Red Sea includes coastal reefs, about 6 thousand years age, stretching along the coast at a distance of 2MIL km.
    • The triangle of coral, which include the reefs of islands in Raja Ampat, West Papua and Indonesia in Southeast Asia, a set of the most bio-diverse coral reefs and more species of coral, estimated at more than 500.
    • The reef of Pulley Ridge, in Florida, which is the deepest photosynthetic  reef of coral in the world.

Deja un comentario