Jeremy touches a sea turtle at the wall break, 25 m deep, San Salvador, Bahamas.
Coral reef accretion continues to be defeated by an influx of disturbances that pose a serious threat to marine ecosystems. Anthropogenic impacts by the human race have administered blows of colossal degrees on reefs across the globe. Pressures caused by anchor damage, vessel groundings, blast fishing, coastal development, recreational activities, coral mining, dredging and numerous other damaging activities have created grave disturbances in coral reef environments. This has greatly hindered reefs’ abilities to recover naturally and so has birthed a new recovery effort. Coral reef restoration has become paramount in the struggle to keep reef ecosystems a thriving bionetwork of the oceans but there is still much more to be determined about the benefits of certain methods. Still in its infancy, restoration techniques are only just beginning to situate themselves among the scientific community. Very little has been decided on these new practices and methods and there is widespread debate on what are the most beneficial choices for reefs, their inhabitants, and their surrounding environments. Numerous techniques and processes are currently being discussed and put to the test including indirect action, reef repair such as triage, restoring structural integrity and restoring topographic complexity, transplantation, artificial reefs, and the use of reef gardening and seeding.
When discussing the revival of coral reef communities two terms have come into use – restoration and rehabilitation. While they may at first seem to be interchangeable a clear distinction has been made between these terms in the scientific community. Restoration is “…used to indicate human intervention that is designed to accelerate the recovery of damaged habitats, or to bring ecosystems back to as close an approximation as possible of their pre-disturbance states” (Yap 841). Rehabilitation, on the other hand, refers to “the act of partially or, more rarely, fully replacing structural or functional characteristics of an ecosystem that have been diminished or lost, or the substitution of alternative qualities or characteristics that those originally present with the provision that they have more social, economic or ecological value than existed in the disturbed or degraded state” (842). The former is the obvious preferred definition for what may be done for coral reefs and so sets up the stage for what are considered to be the most beneficial restoration techniques.
Indirect action is considered to be the simplest and most necessary technique to be applied to coral reef restoration efforts. This method revolves around eliminating the very root causes that have pushed reefs to their damaged positions. Being the least invasive of techniques, it requires solely that the source of disturbances, usually anthropogenic, be removed to rebuild reef health. Some irritations that may be eliminated include frequent vessel groundings, nutrient loading, causes of water pollution, and sedimentation runoff. Without the removal of these and many other disturbances coral reef environments, even with the addition of several other costly restoration actions, will never be able to fully recover and will only continue down their road of destruction (Precht 40-41). Indirect action should always be the first step in restoring reefs to their original splendor.
The second critical method to be considered is that of reef repair. This approach is another fundamental step in restoring reefs and includes “…emergency triage, restoring the structural integrity of the reef framework, and/or restoring topographic complexity” (Precht 41). These restoration techniques aid in reducing further damage after its initial cause and enhance the natural recruitment process. Most if not all restoration projects have included some form of reef repair in their framework.
As mentioned above triage is a key practice in reef repair. This is a term that involves a variety of restoration activities that all revolve around the stabilization and return to the needs of the current reef environment. Technique components involved in this method are “…careful vessel salvage following a grounding event, stabilization or removal of loose sediment and/or coral rubble, removal of debris (foreign objects), and the recovery, storage and/or reattachment of dislodged corals, sponges, and other reef biota” (Precht 41). Vessel salvage will usually include removing objects from deck to increase buoyancy and make removal easier. The stabilization and removal of rubble and debris is imperative to a reef community because storms can easily create a resuspension of these particles seriously affecting the environment. Lift bags, lift vacuums, clam dredges and suction dredges are all put to use in the removal of rubble from a reef area. Numerous adhesive materials can be used in the stabilization practice including epoxy, limestone boulders, and concrete mats. Dislodged corals have a chance for survival if attached soon after a disturbance. Attachment methods include using epoxy, cement, expansion anchors, threaded rods, wires, nails, bamboo skewers, and plastic wire ties (Precht 41). All of these processes further aid in reducing the possibility of secondary damage from a disturbance.
One of the most important features for the flourishing of reef health is its structural integrity. Most often this type of damage is caused by vessel groundings and occurrences of blast fishing. It is of the utmost importance that careful consideration be taken when choosing a substrate material to be used in restoration. An artificial substrate’s purpose is determined by “1) Its structural characteristics (composition, surface, design, and stability) [and] 2) The environmental characteristics (temperature, light, sediment, surrounding biota, hydrodynamics, depth, and temporal effects)” (Precht 43). Structural integrity repair is restoration of the usually unseen cornerstones of the reef.
Another result of frequent vessel groundings, blast fishing, coral mining, and other structurally damaging activities is the loss of topographic complexity. The reestablishment of topographic integrity is vital to the survival of the current collection of plants and animals living in and amongst a reef. The structural features of a reef environment “…greatly affect[s] the species diversity, density and size distribution of both invertebrates and fish…” (Perkol-Finkel, Shashar, Benayahu 122). If the correct form of substrate is not chosen for the repair of a reef structure a whole new reef may come into existence depending on what fish and coral are recruited to the new form of grounding. Differing substrates and varying vertical/horizontal frameworks will attract very different species. Limestone and concrete are the most common and appropriate materials for the restoration of topographic complexity (Precht 43). The method most usually involves placing large boulders or concrete mats over demolished rubble sights or atop sunk or grounded vessels to add suitable stability.
Transplantation has become one of the most popular methods in coral reef restoration. It is seen as the most effective way of providing immediate coral coverage to a damaged reef. The primary objectives of coral transplantation are to improve reef quality, biodiversity, and topographic complexity. Reasons for the transplantation of corals to a site may include a need to:
1.accelerate reef recovery after ship groundings
2.replace corals killed by sewage, thermal effluents, or other pollutants
3.save coral communities or locally rare species threatened by pollution, land reclamation or pier construction
4.accelerate recovery of reefs after damage by Crown-of-Thorns starfish or red tides
5.aid recover of reefs following dynamite fishing or coral quarrying
6.mitigate damage caused by tourists engaged in water-based recreational activities
7.enhance the attractiveness of underwater habitat in tourism areas (Edwards, Clark 475)
There have been numerous advantages and disadvantages found within this method that has spawned intense debate among scientists on the true profit that transplantation may contain for coral reefs. According to scientist Helen Yap there are three areas that need to be well understood before transplantation should take place – 1) knowledge of coral species being used 2) ecological requirements of corals and 3) particular local ecological conditions to which they will be exposed (Yap 1). Some of the most popularly accepted advantages as stated in Edwards’ and Clark’s paper “Coral Transplantation: A useful tool or misguided meddling?” are:
1.Immediate increase in coral cover and diversity
2.Increased recruitment of coral larvae as a result of the presence of transplants
3.Survival of locally rare and threatened coral species when primary habitat is destroyed
4.Reintroduction of corals to areas which are larval supply limited or have very high post-settlement mortality
5.Improved aesthetics of areas frequented by tourists
6.Instant increase in rugosity and shelter for herbivores in bare areas (476)
Disadvantages that are just as quickly merited are:
1.Loss of coral colonies from donor reef areas
2.Higher mortality rates of transplanted corals
3.Reduced growth rates of transplanted corals
4.Loss of transplanted colonies as a result of wave action (attachment failure)
5.Reduced fecundity of transplanted colonies due to stress of transplantation
6.Raised public expectations followed by disillusionment when transplants suffer high mortality (476)
Regardless of these lists it has become increasingly obvious that if indirect action is not first taken and all chronic problems cleared up transplantation will prove to be totally fruitless (Yap 1). In many cases transplantation is carried out before the necessary preliminary actions are taken. Politicians especially look to transplantation as a way to show immediate results for the public who then see that years later the transplants have not survived and loose faith in the benefits of other restoration methods.
An alternative to minimize impacts to donor coral environments can be found in Coral gardening and coral seeding. Coral gardening is the mariculture of corals for use in coral restoration that avoid great amounts of damage and adverse affects on donor populations while providing possible genetic diversity to damaged areas. Coral seeding is also a method of enhancing recruitment for restoration. It involves collecting larvae or coral spawn that has been cultured in the laboratory and then deposited on reef substrate (Precht 45).
Another alternative to natural reef recovery comes in the form of artificial reefs which are “…man-made objects deployed on the seabed for the purpose of influencing physical, biological, or socio-economical processes related to living marine resources” (Einbinder, Perelberg, Ben-Shaprut, Foucart, Shashar 111). These mock reefs are deployed in areas with large amounts of coral destruction and structure loss and may be used to retard the stress on natural reefs in the vicinity (Lan, Hsui 663). These reefs have two ways of arriving at their destinations, either by accident such as sunken vessels and other various submerged rubble or by pre-thought placement. The latter of these is greatly preferred by scientists across the board however debate has also risen on whether these artificial alternatives may actually have a negative affect on its surrounding environments. At the moment few criteria exist for deploying artificial reefs and most of the decisions are based on personal judgment calls (Lan, Hsui 664).
Structural features have proven to be a huge determining factor in the success of artificial reefs. A study was done on how well an artificial reef can mimic its adjacent natural reef communities. It was made painfully obvious that even after centuries if the structural features of the artificial reef are not almost identical to that of the natural then their communities will remain distinct. Impacts include attracting animals away from close natural reefs and bringing new varieties of plants and animals to an area that were not able to be supported before. The latter part, however, may not always be included as a negative impact (Perkol, Finkel, Shashar, Benayahu 2).
Scientists have recently become interested in looking at the affects of artificial reefs on neighboring environments. A study done by exposing heaps of magroalgae to natural grazing areas at various distances from artificial reefs has shown that these false reefs change grazing patterns of ocean animals. This increase in grazing may have many significant affects on the environment such as an increase in fish abundance, an increase in fish variety (depending on the structural features of the artificial reefs), a decrease in the amount of grazing food, and an increase in predation (Einbinder, Perelberg, Ben-Shaprut, Foucart, Shashar 111).
Another important debate sprouted by the increased use of artificial reefs in restoration is called the attraction-production hypothesis. This poses the question of “…whether artificial reefs merely attract resources away from the natural surroundings, thus depleting [them, or] whether they are capable of producing a biomass that would have otherwise been lost without the artificial reef” (Perkol-Finkel, Benayahu 25). The possible benefits of such changes remains controversial making its continued study of utmost importance. A closer look needs be taken in regards to an artificial reefs secondary effects on its surrounding environment and especially upon neighboring natural reefs.
The need for well researched and practiced methods for coral reef restoration has never been more critical. Coral environments around the globe are literally dying out due to an increased human involvement. Various methods are being tested but there are still masses of practices to be learned and put to use. Restoration techniques are vital not only for the reefs they are meant to revive but for the secondary affects reef loss has on all aspects of life. Coral reef restoration may very well be our last chance to conserve this important bionetwork.
Edwards, Alasdair, and Clark. "Coral Transplantation: A Useful Management Tool or Misguided Meddling?." Marine Pollution Bulletin 37(1998): 474-487.
Einbinder, Shai, Perelberg, Ben-Shaprut, Foucart, and Shashar. "Effects on artificial reefs on fish grazing in their vicinity: Evidence from algae presentation experiments." Marine Environmental research. 61(2006): 110-119.
Lan, Chun-Hsiung, and Hsui. "The deployment of artificial reef ecosystem: Modelling, simulation and application." Simulation Modelling Practice and Theory 14(2006): 663- 675.
Perkol-Finkel, S., and Benayahu. "Differential recruitment of benthic communities on neighboring artificial and natural reefs." Journal of Experiemental Marine Biology and Ecology 340(2007): 25-39.
Perkol-Finkel, S., Shashar, and Benayahu. "Can artificial reefs mimic natural reef communities? The roles of structural features and age." Marine Environmental Research 61(2006): 121- 135.
Precht, William. Coral Reef Restoration Handbook. 1st. Boca Raton: CRC Press, 2006.
Yap, Helen. "The case for restoration of tropical coastal ecosystems." Ocean and Coastal Mangement 43(2000): 841-851.
Yap, Helen. "Coral reef "restoration" and coral transplantation." Marine Pollution Bulletin 46(2003): 529.
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