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15 Ocean Coral Reef – Facts – Pictures

by Junita

Beautiful coral reef that are grow underneath of the ocean is actually a symbiotic mutual-ism between a group of animals and algae that is called zooxanthellae. Zooxanthellae is a group of unicelluler algae that do photosynthesis to nourishes themselves an their symbiotic that is animal coral polyp tissue.

Ocean Coral Reef is made of a thousand small animals that is called polyp.  Polyp has a shape like cylinder and have a mouth that located at the upper part of its body. Their mouth is surrounded by tentacle. Then, o ne polyp will grow many and become a colony. They produce calcium carbonate that made their structure strong like a stone. If you, step upon them you will get some scratch and pain, so be careful when you snorkeling or swimming near them.

Although Ocean Coral Reef is a symbiotic mutual-ism between  Ocean Animals and Ocean Plants, some expertise put them into animal family. Their ordo is Scleratinia that produce carbonate as structure of coral reef. Coral reef is live at seashore or at region exposed to the sunlight. Their depth is plus minus 50 meters under sea levels. It is because the alga that live together with coral reef need to do photosynthesis and produce energy for them to life.

Some of the Ocean Coral Reef is live so far under the oceans and don’t expose to sunlight. They are a special species of coral reef that can live without photosynthesis of alga.

Most of the Ocean Coral Reef ecosystem lived in the tropical area and very sensitive with environment changes such as temperature, salinity, eutrofication , sedimetation and the quality of sea. To grow and reproduction, coral reef need to live in water that have temperature around 20 degree celcius, no pollution an waste. Nowadays, there is so much change in our environment because of global warming.

The water become warmer, its temperature is 2-3 degree above normal limit and also there are so much pollution and waste in the sea. Because of that, eutrofication is happened. Eutrofication is a pollution in the water because of phosphate that appeared in water is increasing. This condition make the coral become white, they called it is coral bleaching. The coral bleaching will be followed by the dead of numerous coral reef because there is no photosynthesis activity.

There are many type of coral reefs, the expert classified coral reef into a few of group based on many criteria. Here is the classification of coral reef below.

1.Based on lime production

Based on lime production coral reef was classified into two group, hermatypic and ahermatypic.

Coral Hermatypic

Coral hermatypic is a coral that can produce calcium carbonate. This ability to produce calcium carbonate came from symbiotic mutualism that they made with alga zooxanthellae.

zooxanthellae produces oxygen and organic substrate for nourish the coral.

Otherwise the coral provides inorganic component such as nitrat, phosphat and carbon dioxide.

The alga needs these inorganic component for live. At the end, Calcium carbonate will be produced and made strong structure for coral reef. Hermatypic coral reef lives at tropical region near the seashore when there is abundant of sunlight. They grow by following sunlight. This characteristic is called photohtropic positive.

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Ahermatypic corals

One of Ocean coral reef type is Ahermatypic corals. Its don’t produce a calcium carbonate. They are live deep under the sea and don’t make a symbiotic mutualism with alga.

This type of coral do not have a symbiotic mutualism with zooxanthellae, a type of unicelullar algae such as Dinoflagellata unicellular Gymnodinium microadiatum which present in coral polyp tissues and carry out a photosynthesis.

This type of coral get the food for survival with catching a nutrient from the water around them. You can find ahermatypic coral in almost every ocean.

See also: Climate of the Ocean

This is different from hermatypic coral that only can find in tropical area.

2.Based on its shaped

Based on its shaped and where they’re living, coral reef is classified into reef, coral, reef coral, coral reef.


Reef is massive sediment of calcium carbonate (CaCO3). Many animals and other creature such as lime alga and mollusca tend to produce these inorganic products.

Mollusca is a type of animal that don’t have vertebrae such as octopus and squid.  The reef is formed in the shallow sea area, they usually is called as the back of the sea.

This area is full of colorful coral reef. It is look like a flower in the ocean. You can enjoy  the beauty as you enjoy the garden full of flowers when you are in the land.

This place is the most favorite to has a beautiful under sea photograph. Make sure you have a good underwater camera for take that as a your unforgettable memory.

See also: Ocean Problems


Coral is a group of animals from ordo Scleratinia and phylum Coelenterata, This animal has stadium polyp in its life cycle. Then, the polyp will grow into thousand or million of polyps and is arranged in stacked then their size become bigger as a colony.

They also produce calcium carbonate to strengthen their structures. If you go to the seashore you will see many stone underneath the sea, it is coral. Some people called it as a stony coral. because of their structure that look like a coral.

Be careful when you swim around them because it can hurt your leg and also there are a jellyfish. Jelly fish has toxin that can blister your leg.

See also: Global Warming in Ocean

Reef Coral

The primary structure of reef is also called hermatypic coral. This reef coral is dominant coral that produces lime because they have a mutualism symbiotic that can do a photosynthesis so they can produce calcium carbonate.  Calcium carbonate is a molecule that they need for make a rocky structure of coral reef.

Because of that, reef coral is different from other reef coral that don’t produces lime we called it a hermatypic coral, and also different with cadas rock or volcanic rock. The cadas rock or volcanic road is a stone is made of sedimetation of the ocean and the volcanic activity.

They are easy to find in the ocean near the active volcanic area.

Coral Reef

Because of million coral reef become one they made a huge ecosystem. The ecosystem is made of many animal especially coral rock and alga that produce calcium carbonate.

Because of that the coral reef is a living place of many fish, necton, plankton and animal of the sea such as octopus, squid, crab, sea cucumber, porifera, polichaeta and tunicata. Coral reef is a place for this animal to seek a food for their nutrient. It is also can be a shelter for some animal, such as squid, shrimp, schoolfish, and many other animal.

Here are also a living place of some shellfish. It can be one of our country devisa because the shellfish can produce beautiful pearl.

See also: Marine Energy

3.Based on their location

Based on their location, coral reef is divided into three types, fringing reef, barrier reef, atoll.

Barrier reef

Barrier reef is almost similar with fringing reef. But these type of reef is grow further to the ocean, around 0.54 km until 1 km from seashore and have a depth around 75 meter under the sea level.

Sometime the barrier reef will grow circle and made a ocean pool called lagoon.  This lagoon is relative safe for swimming, diving and also fishing because its waves aren’t big as the ocean. Even thought, the length of lagoon is ten of kilometers.

Barrier reef grows very big and long, it can surround a whole big island even a continental. One of the biggest barrier reef is located in east beach of Australian continent the name is Great Barrier Reefs. They appeared like a highland under the sea if you see them at mainland.

They are concantenated to form a cluster of coral islands. In Indonesia, the examples of barrier reef types is in Batuan Tengah beach in Bintan island, Riau archipelago, Spermonde beach in South Sulawesi, Banggai archipelago in Central Sulawesi.

Ring Coral reef

Ring Coral reef or also called attols is a coral reef that consists of many coral reefs are arranged to form a ring or a doughnut.

Sometimes, Attols looks like similar as big islands and found in tropical area in atlantis ocean.  These types of reef actually surrounding an island like greet barrier.

However the islands sink to the deep sea so that their look is like a ring with a hole in it. Based on the theory of Darwin, the development of ring coral reef is happened because of volcanic activity that caused many islands sink under the sea.


There are other reefs which live in Ocean, as follows:

  • Fringing reef

Fringing reef is a coral that located at the edge of ocean. It is the simplest type of coral reef. You may see this typed of coral reef at seashore in tropical region. Fringing reef can grow to a depth of 40 meter under the sea level. They surrounding a whole big islands and grow up and outside to ocean.

When they are growing, coral reef grow circular that marked with a tire shaped or part of sediment of dead coral. When coral reef meet a steep beach, the coral reef is growing up vertically and follow the coastal cliff. The example of this type of coral reef is Bunaken which is located in Manado city North Sulawesi, Nusa Dua beach which is located in Bali and panaitan beach in Banten.

Read also: ocean in the world

So, here the story of development coral reef based upon Darwin theory. The coral reef is start to growing surrounding the new island. This condition cause the growing is always to upper direction and a wide to ocean. They are look like fringing coral. Then, there is volcanic activity, the island start to sinking under sea level and leave the seashore away some kilometers then we called it barrier reef. After that, the island is completely sinking and leaving the reef. Then, the reef become circular and become a ring coral.

Read also: ocean environment

Zoning area

Based on zoning area, coral reef is classified into two types. There are windward reef and leeward reef.

  • Windward Reef

Windward reef is a coral reef that facing the direction of wind. Their slope faces the great ocean and dominated with no symbiotic coral reef. So the coral is made of ahermatypic coral that is ending at shallow ocean.

  • Leeward Reef

Leeward reef is a reversal of windward reef. This reef is located backs of the direction of wind. Different from the other type, this type is merely a overlay coral reef and has a lot of sedimentation. Because of that, this reef is not fit to become a habitat many fishes and sea plants.

Beside these classification above, there are some unique coral reefs. They are patch reef, microtoll, cays, and seamount or guyot.

  • Patch Reef :The patch reef have a flat appearance and grow in a lagoon area. Some people, classifying this reef into fourth reef in location classification after fringing reef, barrier reef and attol.
  • Microattol : Microattol is a flat colony of coral that cannot grow up to above but grow widen to the side direction. It appearance looks like a ring but smaller than ring coral reef. So that, they call the reef as microattol
  • Cays : Cays ia small island that made of a heap of material. This materials is accumulated above the coral reef. Then, they become one island The example is an small sand island in Maldives
  • Seamount or Guyot : Similar with ring coral reef, seamount is also appear because of volcanic activity. They actually is a coral reef that grow near volcano. When, the volcano is eruption, the coral reef is sinking under the sea.

See also: Acidification of the Ocean

Conservation of coral reef

As the time goes by, the modern world give another bad impact to environment. Global warming is made the water become hotter than before and there are a lot of waste that throw to the sea. Because of that, the coral face the difficulty for survival in ocean. There are some transplantation technique for conservation of coral reef, as follows:

1.Artificial Coral Reef

The principal of this technique is provide a place for fishes and sea creature for living and produce organic substrate. Therefore, this substrate is used for living of coral reef. The place is made of construction material such as concrete structure that have a shape like a dome or pyramid. Then, this structure is sinking to the ocean near the still living coral reef. The expert hoping that this structure can stimulate the coral reef grow wider.

2.Transplantation Coral Reef

The Principe of this method is similar as transplantation plant at mainland. This method is done by cutting a part of healthy coral reef then planting it to the area that have a damaged coral reef. We hope that the part of healthy coral reef can stimulate and accelerate the growing of damaged coral reef in other area . the most used coral reef for transplantation is Acropora. Because this coral reef has a fragile branch therefore this coral reef is easy to cut and have the greatest height for a month than other species of coral.

3.Mineral Accretion

This method is use DC (direct current)  and low voltage electricity for stimulate the growth of coral reef. This electricity is flowing through steel wire where the coral reef is hanging upon it. This method is successfully increasing the rate of growth of coral reef 3-5 times faster than other usual transplantation method. This method is developed by biological expert. Their name is Thomas J. Goreau and Wolf Hilberts.

See also: Types of Sea Urchins

Factors for Conservation of Coral Reef

As we know at the very first of this article, the coral reef can grow beautifully if there is enough sunlight, good temperature and enough amount of rainfall and other factor. If one of that factor is unfulfilled, then the coral reef become dead and white. Here are the factor that we need to know to maintain the beauty of our coral reef.


Naturally, the temperature of water is different based on the level of ocean depth. Water in the deep area is more salinity and colder than shallow area. Because of many factor that happened in ocean such as change climate and global warming, there is up-welling phenomenon. The colder water in a deeper level go up at the level of living coral reef. Then, the temperature of water where the coral reef is growing become change and making the growing of coral reef slower.

Read also: Ocean Phenomenaocean layer


As the other living things need sunlight to survival, the coral reef is also need sunlight for photosynthesis. Photosynthesis is doing by alga Zooxanthella to produce energy and oxygen for their survival  and their growth. The amount and quality of sunlight is a pivotal factor for determined the growth of coral reef. As the deep ocean the sunlight can’t go through the water so the coral cannot grow abudantly in a deep ocean.

3.The Clarity of Water

If the clarity of the water is low. The sunlight can’t go throuh the water and meet the coral reef. This is happened because of a lot of sedimentation of mud and sand tha covered the water. Beause of that, the coral cannot produce energy and oxygen and become dead coral.

4.The Depth of the Ocean

From expert opinion, the maximum depth of coral reef for living is 40 meters under the sea. In this depth, they still can take the sunlight. But there is an ideal depth for them, it is 20 meters under the sea.

5.Temperature of Water

Coral reef can live beautifully at temperature 25- 29 degree celsius. Their minimum temperature for living is 15 degree celsius. They still can live but ther are some troubles for their growth and metabolism at that level of temperature.  The maximum temperature for coral reef is 36 degree celsius.

See also: Effects of Sea Level Rise

6.Salinity of water

Salinity of water is a percentage of salt in the water. The optimal salinity for coral reef is 27-40 % with average level is 36%. The salinity of sea water can lower  because of the flow water from river to sea is too much. Lower salinity made, the coral reef cannot produce calcium carbonate for living. Then, they will died and the colony is decreasing.

7.Level of Sedimentation

If the sedimentation is too high, It can decreasing the amount of sunlight that is going through the sea. This sedimetation can also obstruct the nutrient pore of coral reef. Therefore, the sedimentation is slowing the coral reef growth.

8.The Wave

Wave in ocean is needed by the coral that live in the relative closed water. This is happened  because  the alga Zooxanthella can’t produce oxygen at night. Therefore, the reef is lack of oxygen.  If there is a wind at the surface of water , the coral reef still can survive at night because there is plenty oxygen from another place that is carried by the water  flow. If the waters just stop in one place there is no change of oxygen and carbon dioxide


The primary of coral stone can only attached to the strong and hard substrate such as shells, dead coral and a skeleton from other organisms.

See also: Effects of Ocean Currents

Although, there are many modern method for conservation, the government need to build the good strategic to collaborate many stakeholder such as community near the seashore, technology, fund  , material with good policy. Therefore, we as a human have to love our environment especially our ocean.

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