Corallian transplanation — Wikipedia
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The transplantation corallienne is an operation consisting in transferring coral colonies or fragments of donation colonies and transplanting them directly to a degraded site [ first ] . This is one of the techniques of the ecological restoration of corals, it is not valid to reconstruct degraded large -scale areas.
The coral reefs are classified among the most productive and biodiversity ecosystems in the world. They play a leading economic role for human populations by providing several economic goods and services such as tourism, coastal protection and fishing [ 2 ] .
These environments are faced with a global crisis due to global warming, pollution and various discharges, the overexploitation of resources and destructive fishing practices (cyanide, dynamite) [ 3 ] which weaken their natural recovery capacity.
Ecological restoration makes it possible to restore an ecosystem which has been degraded, damaged or destroyed in order to bring it as close as possible to its original conditions. There are two types of restoration one physics and the other biological [ 4 ] including coral transplantation.
Physical restoration [ modifier | Modifier and code ]
The physical restoration of reefs focuses on repairing the reef environment and can cost a hundred thousand to several million dollars per hectare [ 5 ] .
Examples of physical catering actions are the triage and repair operations of damaged reefs and the use of artificial reefs such as limestone blocks, modules designed in concrete (eg Reefball) or ceramic (eg Ecoreef) , minerals (Brucite and Aragonite) deposited by electrolysis on meshed metal structures (eg Biorock) [ 5 ] .
This type of restoration could be a prerequisite for increasing the chances of success for biological restorations [ 4 ] .
Organic catering [ modifier | Modifier and code ]
Biological restoration takes into account as the physical and biotic environment. It can be done in the form of indirect or passive management measures through a range of coastal management actions which reduce anthropogenic pressures on coral systems, or direct active measures (most often active catering consists in transplant corals and other biotes) on a degraded site. During the transfer it is crucial to minimize damage to healthy (or less degraded) “donor” recipe areas from which the transplants are obtained, and to maximize the survival of transplants on the reef that is restored [ 4 ] .
Coral is an animal, it does not move as easily as an inert piece of rock and has requirements in terms of its living conditions. In this perspective, coral transplantation must pay attention to several conditions [ 6 ] :
- temperature,
- the luminosity,
- salinity,
- water cleanliness.
The transplantation of corals is used for several types of significant economic interest services such as safeguarding of endangered or rare species, the development of tourist sites and compensation measures for the destruction of the natural environment [ 5 ] .
Corail transplants supply [ modifier | Modifier and code ]
Coral transplants are collected in the form of small fragments (3 to 10 cm ). They are used to minimize the losses and then they will be raised for a while on-site In benthic nurseries where they can be cultivated in small colonies which are then transplanted. In cases where reefs are threatened by backfilling work or industrial development (eg power plant) [ 7 ] , whole areas of reef can be transplanted and fully moved colonies to a refuge site. This method is not recommended given the high probability of mortality of transplants. The “corals of opportunity” which are broken coral fragments generally represent a source of transplants [ 8 ] .
In intact donor colonies, the supply of transplants should not use more than 10% of their surface to minimize stress. It is not recommended to drill massive colonies to obtain transplants but it is preferable to take fragments around the colonies [ 5 ] .
Culture and fixation [ modifier | Modifier and code ]
Coraux can be successfully cultivated from asexually produced fragments or larvae produced by sexual reproduction. The main reason for the cultivation of asexual fragments is to maximize the benefits from a given quantity of source materials and thus minimize damage to the donor areas. But there are precautions to take to ensure the genetic diversity of cultivated transplants. Culture from larvae has been carried out experimentally but requires more technical expertise than asexual culture [ 5 ] . However, sexual propagation in culture has the potential to produce huge amounts of small corals. The large question mark remains if the corals will survive well when transplanted on a degraded reef.
The species which naturally reproduce by fragmentation are capable of self-fixing in a few weeks, if they are transplanted into stable reefs.
On exposed reefs, a variety of epoxy adhesives, cements, threads and cable clamps are used to fix transplants on degraded reef areas. Materials like nails and staples are to be avoided in the reef environment [ 5 ] .
The most effective method will depend on:
- the size and form of growth of transplants;
- habitat exposure to the actions of currents and waves;
- The nature of the reef substrate.
Choice of species [ modifier | Modifier and code ]
It is recommended to transplant species with the capacity to survive under very similar environmental conditions or identical to the reference ecosystem. The use of species mixture can create a balance in the site, for example, connected species have a high growth rate but also a tendency to be more sensitive to whitening, stress of transplantation and diseases. While massive and sub-massive species have lower growth rates and a tendency to survive in the face of these same disturbances.
Sizes, density and transplant period [ modifier | Modifier and code ]
For transplants obtained asexually (fragmentation) a minimum size of approximately 5 to 10 cm can offer better chances of survival [ 5 ] . On the other hand a size of 1 cm is enough to cultivate sexually products transplants. But in general larger transplants seem to survive better.
The density depends on the state of degradation of the reef; For example on a reef already with coral coverage of around 20%, two individuals can be transplanted/m² while on reefs completely bare of corals it is recommended to transplant around 25 individuals/m² [ 5 ] .
The optimal period of transplantation is a few months before or after the maximum ocean temperatures and outside of laying periods for species that lay seasonally.
Interview [ modifier | Modifier and code ]
The development of transplanted reefs is a process that lasts several years. The monitoring of catering projects is essential to assess the success and profitability of transplantation. With this in mind, maintenance visits are recommended as well as regular data collection.
Bibliography [ modifier | Modifier and code ]
- Alasdair Edwards and Edgardo Gomez , Restoration Reef: Concepts & Recommendations , The Coral Reef Targeted Research & Capacity Building for Management Program, , 38 p. (ISBN 978-1-921317-00-2 , read online )
- (in) Alexander J. Edwards (editor), Reef Rehabilitation manual , The Coral Reef Targeted Research & Capacity Building for Management Program, (ISBN 978-1-921317-05-7 , read online )
- (in) Yael Horoski , Ecological and physiological aspects of the restoration of coral reefs: transplantation of culture corals on a degraded reef , ( Online presentation , read online )
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