The coastlines of more than 100 countries are protected by coral reefs (Johnson et al, 2011).  It has been estimated that one billion people depend on coral reefs for their livelihoods (Ref. WWF reports.)  The loss of coral reefs will have a devastating effect on the lives of more than one billion people and their surrounding mesocosms.

One of the largest benefits of coral reefs is the tourism industry - tourism adds trillions of dollars to the global economy and affects the majority of residents in surrounding communities. Coastal and marine tourism (known as the “Blue Economy”) supports more than 6.5 million jobs worldwide (UN Environment Program Reports).

The Nature Conservancy’s “Mapping Ocean Wealth” (MOW) research efforts (2017) showed that more than 70 million trips are made to the world’s coral reefs each year. 


In total, coral reefs provide a $36 billion benefit to the global economy. Of this $36 billion, $19 billion is derived “on-reef”  from activities such as scuba diving, snorkeling, glass-bottom boating and wildlife watching - the other $16 billion comes from “reef-adjacent” tourism such as enjoying beautiful views from beaches, dining on local seafood, paddle boarding and other aquatic activities. In fact, reef zones generate more than one million dollars per square kilometer of coral reef (UN Environment Program Reports.)


Coral reef restoration projects are running to be one part tourism industry. The report by The Coral Reef Alliance (CORAL) (2014), showed that coral reefs protection and restoration programs aid the growth of hospitality businesses. Ecotourists have higher incomes than regular tourists on average, and they tend to spend more money while traveling. Attracting this growing market could help hotels increase their income.  In 2017, The New York Times reported that luxury hotels and resorts have started to coral reef restoration programs as their priority.

Here three examples of coral restoration programs which is running with tourism companies


 The Brando Resort

The Brando Resort and its partners (Tetiaroa Society and Te mana o te moana) are working on coral reef restoration in French Polynesia. They are also looking towards the future.


The resort’s has its own Ocean Acidification Program to do sweater chemical analysis of the water around coral to monitor of reef health. Oxygen, pH, and other chemicals tell how fast the reef is growing, and help predict the reef’s future health. The resort is also experimenting on part of the reef to simulate conditions 100 years from now, which helps predict the fate of coral reefs in response to climate change.


Banyan Tree Vabbinfaru 

In the Maldives, Banyan Tree Vabbinfaru resort is another example of reef restoration programme with ecotourism industry. They are using Asexual propagation by electrochemical method to promote the deposition of calcium carbonate through the process of electrolysis of sea water that helps to corals grow faster.


A low-voltage electrical current in the metal nursery bases to coral restoration programme helps to deposit as calcium carbonate faster in the metal bases and coral can use them to its skeletons.


This electrical voltage help coral grow faster and healthier. So far, the results are positive. The volcano-shaped steel structure on Vabbinfaru, called the Lotus, provides corals and fish with a healthy habitat and is a great opportunity for snorkelers to see the birth of a new coral reef.

Underwater Hotels 

Creating underwater Hotels is another example of increasing the necessity for coral reef restoration programmes in the tropical areas.


Maybe the best example is Maldives Rangali Island resort.  A first luxury two-level residence with name Muraka which has a master bedroom submerged over 16 feet below sea level in the Indian Ocean. 


From Dubai to the Maldives, these underwater hotels offer the chance to see fish swim by your window, all in the most luxurious of settings. In order to have the a beautiful view in these hotels, they need to have coral restoration as a part of their long terms hotel projects. 


     In order to have a successful Coral reef restoration, it is needed a high insufficient knowledge of coral biology and environmental science. Coral reef restoration is not look like the forest restoration and its success is not always guaranteed. The technology of active coral reef restoration has a history of only 40 years or less (Omori, 2019). 

Three coral reef restoration techniques are tested globally successfully

  1. Asexual propagation using nursery-farmed coral fragments

  2. Electrochemical method

   3. Techniques using sexual propagation 

The “coral gardening” technique is a cheapest and easiest method which has been applied successfully at high scales in the world. Coral restoration using sexual propagation technique need to high experience, scientific studies technology, an intensity work and a high costs than the asexual propagation techniques (Omori, 2019). Coral restoration using sexual propagation technique need to high experience, scientific studies technology, labour intensity, and a high costs than the asexual propagation techniques. The coral genus Acropora as knows as a fast-growing corals in the world, it is considered to be an important coral for reef restoration through Asexual and Asexual Techniques.  


Asexual propagation using nursery-farmed coral fragments

In this method a large number of small fragments (~3 cm in length) clipped from donor colonies and attach to an artificial substratum and kept in a nursery for some period until they grow to a size adequate for outplanting. The process of fragmentation to get from one clipping to many outplanted corals called coral gardening (Baums et al, 2011).  More details has been described in the Baums et al, (2011).


Fragments taken from donor colonies should be transported in a short period of time (less than 24 ha) to the nursery site to minimize stress and placed in the shade to maintain temperature and reduce exposure to sunlight while transporting.  The important things before starting the coral gardening pogramme, doing a case study pilot work to see if the selected site is capable to support coral gardening project.   As we mentioned already, the success  of coral restoration project is not always guaranteed. 


Even the most experienced reef ecologists may not be able to fully predict the potential of a location as a good nursery site. Even when all physical and biological factors described here have been considered, there may be some unexpected or unmeasured factor that may jeopardize the long-term survivorship and growth of corals at the selected sites. However, if in the coral gardening pilot test, the coral mortality was not more than 25% after two or three months, this test can be used to formally the nursery sites project.


There are some important parameters that we need to consider before choosing the project to to promote nursery success. The most important parameter is we need to be sure the cutting fragment from donor colonies will be have the minimum impact on donor. The small colonies of corals will not be suitable to getting samples. The select site as a donor need have the capacity to provide thousand and thousand coral fragments.


And try the project in a small reef area will be damage the form donor colonies and project success will be decrease with low number of coral fragment. When we got sure about donor coral site, we need to consider some parameters before choosing the mercury site, it is important we choose a nursery site close to the outplanting site to minimize the coral transport from nursery to the outplanting site as well as the project costs. The Existing Wild Populations in the outplanting and nursery sites, water quality, such as temperature and light, water movement and anthropogenic parameters are important before starting the project. ​

(Baums et al, 2011)

Asexual propagation using electrochemical method

In this technique with providing a small voltage of electrical energy with range ∼1.7 to ∼2.8 ± 0.1 A (Romatzki, 2014; Goreau, 2014) on coral transplanting bases, we enhance growth of coral transplants is the called electrochemical method or mineral accretion method.


This method was created based on the principle of seawater electrolysis inducing a direct current between two electrodes immersed in saltwater. The chemical reaction of electrolysis leads to an increase in pH near the cathode, shifting the concentration gradients of dissolved minerals such as dissolved inorganic carbon (DIC).


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This DIC around the cathode precipitates on the structure as aragonite and brucite, which both increase the structure’s stability with ongoing accretion. Since physiological processes for coral skeleton growth involve DIC uptake, the highly concentrated DIC is postulated to be more readily accessible for uptake by transplanted. Corals growing on these electrified artificial reefs tend to grow 3-4 times faster, and survive much better during bleaching events, disease outbreaks, and other disturbances (Goreau, 2012).
The Mineral Accretion technology uses low-voltage direct current trickle charges to grow self-repairing limestone structures of any size or shape in the sea. This technique has been shown to greatly increase the settlement, healing, growth and survival and to enable resistance in corals, intertidal salt marsh grasses and coral forming marine organisms to stresses such as extreme high temperatures, sedimentation, and eutrophication ( 

Coral Restoration using sexual reproduction


As described above, using sexual propagates requires more, knowledge, efforts, costs and technology than the asexual propagation techniques (Omori, 2019). However, using sexual propagates have a lot of benefits and advantages. It creates a big genotypic diversity between corals when they grow successfully and become a mature colony. The new corals have more adaptively, evolutionary potential and a high resistance to anthropogenic parameters such as climate changes, seawater pollution and etc.  The coral restoration using sexual reproduction has also strong potential for creating big scaling of restoration reef areas (Omori, 2019).         

The broadcast spawning and brooding are two reproduction strategies in coral for larval rearing.  Broadcasting species release eggs and sperm into the water column for external fertilization and subsequent larval development. In the brooding corals, fertilization occurs within the polyp and fully formed larvae (planulae) are released. Broadcasters usually spawn only once each year, while brooders often reproduce for several consecutive months. Corals may also be either hermaphrodites (polyps produce both eggs and sperm) or gonochoric (polyps have separate sexes). Fish around the corals may swim excitedly around spawning time and this behaviour may be an additional indication of spawning (Omori, 2019). Methods of farming sexually propagated corals and outplanting for coral reef rehabilitation are well described by Omori and Iwao (2014).



There are a very few successful cases of artificially induced coral spawning. However, it can be accomplished with some Acropora and Montipora species using hydrogen peroxide. Add hydrogen peroxide (2 mM for 3 h exposure time or 5 mM for 2 h) after transferring the fragments of a mature colony from the sea to a container on land. After that, rinse the fragments to remove the hydrogen peroxide and transfer them into clean, continuous flowing seawater for spawning. Spawning by artificial induction occurs from 20:00 to 23:00 h under natural lighting, similar to natural spawning in the sea (Omori and Iwao, 2014).


In general, Coral Restoration using sexual reproduction explains, how we are able to collect coral gametes from sea and provide laboratory conditions to eggs fertilization and larval transformation into a coral small colony.

Flowchart of the techniques for reef restoration with outplanting of sexually propagated corals Omori and Iwao (2014).


Cost estimate  for Asexual propagation using nursery-farmed coral fragments in Brazil 

Brazil did not have yet any coral restoration programme, then it needs some studies to have a clear vision about the costs for all type of coral restoration programmes. I  estimate that the cost of asexually propagated coral using The “coral gardening” technique will be US$ 30,500-148,000 per year approximately for two Scenarios.  
The cost for coral restoration varies significantly according to the method and local condition (Omori, 2019). Any environmental parameter such as nursery distance from the harbour and depth of the nursery are factors that influence the cost (Omori, 2019). with considering the economical benefits of coral reefs  in local and global level to area and people, It will be worth.