These techniques may focus on theorganismal scale by enhancing or restoring lost corals and associated biota e.g., transplantation,artificial reefs or on a broader ecological scale by re
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Beth Zimmer
CONTENTS
3.1 Introduction 39
3.2 Restoration Techniques 40
3.2.1 Indirect Action 40
3.2.2 Reef Repair 41
3.2.2.1 Triage 41
3.2.2.2 Restoring Structural Integrity 42
3.2.2.3 Restoring Topographic Complexity 43
3.2.3 Transplantation 44
3.2.3.1 Alternative Transplantation Techniques 45
3.2.3.2 Transplantation Questions and Research Needs 46
3.2.4 Artificial Reefs 46
3.3 Cost of Coral Reef Restoration 47
3.4 Success of Coral Restoration Techniques 48
3.4.1 Indirect Action 48
3.4.2 Reef Repair 48
3.4.3 Transplantation 48
3.4.4 Artificial Reefs 49
3.5 Future of Coral Restoration Research 49
3.6 Summary 50
References 50
3.1 INTRODUCTION
Disturbances in coral reef environments have occurred since the evolution of corals and throughout geologic time to the present Prior to human existence, natural impacts such as those resulting from storm events, temperature variations, and ultraviolet light exposure had periodic detrimental impacts
on coral reefs Anthropogenic impacts to corals have occurred throughout human history, ranging from collection in early history to vessel groundings, anchor damage, blast fishing, coral mining, dredging, coastal development, water quality degradation, recreation, and others in recent history Beginning in the late 1970s, coral reef scientists became alarmed by the rapid, widespread decline
in coral reefs around the world resulting from a variety of causes, including coral disease, coral bleaching, and anthropogenic impacts.1–5 The time required for the natural recovery of a disturbed reef is usually on the order of decades.6–14 However, after a severe disturbance that significantly injures reef structure, the reef can require centuries to recover15–17 or never effectively recover on
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The global decline of reefs is of particular concern to the scientific community because the generalconsensus among researchers is that coral reef accretion is currently outpaced by the rate of human-induced destruction.11,14,23,24 This consensus has inevitably elicited attempts to shift the balance byrestoring damaged coral reefs Coral reef restoration projects and studies have been implemented toprevent injury to corals that would be adversely impacted by planned activity, to hasten coral reefrecovery from anthropogenic or natural impacts, to enhance fisheries habitat, and to enhance theaesthetic appearance of reefs for tourism Throughout this chapter, the term “restoration” will be used
as a general term to encompass the restoration, rehabilitation, and creation of coral reefs
As a science, coral reef restoration faces a variety of challenges including the dire state of coralreefs around the globe, the wide array of disturbances and subsequent ecological responses, andthe complexity of the coral reef ecosystem.25 The science of coral reef restoration is in its infancyand lags far behind related terrestrial and wetland sciences.14,26–31 Even seagrass restoration science
is more highly developed.32,33 During the initial research for this chapter, it became quite evidentthat while research relating to restoration techniques is available, a significant lack of published,peer-reviewed literature on actual restoration projects exists Many restoration projects have beendesigned and carried out in an ad hoc manner, without long-term monitoring for success Datafrom unpublished studies is available in the form of gray literature or merely article abstracts Thischapter outlines the currently available restoration techniques and identifies additional researchneeds in coral reef restoration science
3.2 RESTORATION TECHNIQUES
A variety of restoration techniques have been explored thus far, including indirect action, reefrepair, transplantation, and the installation of artificial reefs These techniques may focus on theorganismal scale by enhancing or restoring lost corals and associated biota (e.g., transplantation,artificial reefs) or on a broader ecological scale by restoring the structure of the reef itself and/orattempting to maximize natural recruitment (e.g., indirect action, reef repair) Available informationwill be summarized for each restoration technique, including a brief description of the techniqueand examples of restoration projects that have implemented it In a restoration plan, techniqueshave been used individually or in combination
The simplest and most essential technique that can be applied to restore a coral reef is to eliminatethe source of anthropogenic disturbance(s) causing detrimental impacts to a reef Such anthropo-genic factors might include nutrient loading, anthropogenically induced runoff and sedimentation,water discharges, or frequent injury from vessel groundings Reefs that are undergoing chronicdisturbances will not recover naturally,10 and failure to remove the source of the chronic distur-bance(s) will render other restoration efforts futile.34–37 Therefore, when applicable, this restorationtechnique should be applied to all restoration projects; that is, anthropogenic sources of disturbancemust be eliminated or at least reduced to a sustainable level in order to achieve “restoration.” Thefollowing are examples of restoration projects that have implemented indirect action:
• Sewage outfalls were diverted to reduce nutrient loadings in Hawaii.38
• Activities causing land-based erosion were discontinued to reduce sedimentation inHawaii. 39
• Thermal power plant effluent was diverted into deeper offshore waters in Hawaii.40
• Coastal discharges of silt-laden water and bagasse (fibrous residue from pressing sugarcane) were terminated in Hawaii.41,42
• Vessel deterrent devices (radar response transmitters) were installed on navigational aids
in the Florida Keys as mitigation for the Containership Houston grounding.43 2073_C003.fm Page 40 Friday, April 7, 2006 4:38 PM
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Although this technique is critical for a successful restoration project, one disadvantage isthat, by itself, indirect action may not result in complete restoration of the damaged reef If thereef has experienced very severe damage (e.g., large-vessel grounding, coral mining, blastfishing), it may require centuries for natural recovery or never fully recover For this reason,indirect action may be used in combination with other restoration techniques.44,45 In addition,the cost of this technique may be prohibitive,46 depending on the individual circumstances(materials, equipment, labor, etc.)
3.2.2 R EEF R EPAIR
Reef repair may consist of emergency triage, restoring the structural integrity of the reef framework,and/or restoring topographic complexity These techniques attempt to minimize additional damagefollowing a disturbance event and enhance natural recruitment The vast majority of comprehensiverestoration projects have included some component of reef repair
Coral rubble and sediment resulting from a disturbance event can increase secondary damage
to the reef from resuspension during storm events.50–52 In addition, the presence of unstablesubstrate or a layer of fine sediment may delay reef recovery by inhibiting the settlement andgrowth of corals.22,51,53–55 Removal or stabilization of the loose rubble reduces secondary damage,increases substrate stability, enhances recruitment, and increases habitat complexity.50,54,56 Rubbleand/or debris (vessel fragments, foreign objects, etc.) may be removed from the damage siteusing lift bags, lift vacuums, clam dredges, or suction dredges.49,51 Rubble can be stabilized inplace using adhesive materials such as epoxy or overlay structures such as limestone boulders
or concrete mats The potential exists for sponges to aid in rubble consolidation by temporarilystabilizing rubble until carbonate-secreting organisms permanently bind the rubble to the reefframework.56
Following disturbance events such as anchor damage, vessel groundings, and dredging damage,triage may involve the emergency recovery of dislodged corals and surviving fragments.51 Dislodgedcorals in shallow, high-energy environments may be subject to mortality from inversion, burial, ordisplacement.49,57 Dislodged corals that are recovered can be immediately righted and/or reattached
or can be stored in a similar, safe environment until reattachment is feasible.49,51 Reattachmentmethods might include the use of epoxy, cement, expansion anchors and threaded rod, wire andnails, bamboo skewers,58 and plastic wire ties,43,57,59–61 or any of the methods utilized for transplan-tation (see Section 3.2.3) The following restoration projects have employed triage methodologies:
• Toppled corals were righted, coral fragments were stabilized, and debris was removedfollowing vessel mooring chain damage in Guam.62
• Toppled corals were righted following anchor damage in St John, U.S Virgin Islands.43 2073_C003.fm Page 41 Friday, April 7, 2006 4:38 PM
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• Dislodged corals were reattached after damage from a fiber optic cable installation inFlorida.63
• Dislodged corals were salvaged and reattached, and rubble was stabilized with epoxyfollowing a vessel grounding (Containership Houston) in the Florida Keys.45
• Corals dislodged from anchor and grounding damage were reattached following a vesselgrounding (C/V Hind) in Florida.64
• Dislodged corals were salvaged and reattached following a vessel grounding (M/V Firat)
• Hull paint, rubble, and debris were removed following a vessel grounding (M/V Horizon)
in St Maarten, Netherlands Antilles.68
• Metallic vessel debris was removed following a vessel grounding (Jin Shiang Fa) inRose Atoll, American Samoa.69
• Rubble and sediment were removed and dislodged corals were reattached following avessel grounding (M/V Wellwood) in the Florida Keys.70
• Concrete mats were deployed to stabilize rubble at a coral mining site in the Maldives20,52
and over the Containership Houston grounding site in the Florida Keys.43,45
• Corals were salvaged and reattached, and rubble and vessel debris was removed following
a vessel grounding (R/V Columbus Iselin) in the Florida Keys.71
• Debris and radioactive material were removed from Enewetak Atoll following nucleartesting (refer to Chapter 15 for additional details)
3.2.2.2 Restoring Structural Integrity
A catastrophic disturbance can drastically damage the structural integrity of the reef framework,creating fractures, fissures, gouges, or craters in the reef limestone This type of damage is oftenthe case in large-vessel groundings51,70 and blast fishing.72 Repairing structural framework damagecan prevent further structural deterioration and will minimize or avoid the potential for secondarydamage produced from rubble and sand.51 Techniques for restoring structural integrity have beenused mostly for large-vessel groundings Examples of projects where the reef framework wasrepaired include the following:
• Fractured reef framework was grouted with Portland cement and molding plaster forstabilization following a vessel grounding (M/V Wellwood) in the Florida Keys.70
• Craters that threatened the structural stability of the reef, created by the grounding ofthe M/V Alec Owen Maitland in the Florida Keys, were repaired using gravel fill andconcrete armoring units.73,74
• Craters created by the grounding of the M/V Elpis in the Florida Keys were repaired byfilling them with rock and rubble from rubble berms caused by the vessel impact, alongwith boulders and sand transported to site.75
• Gouges and cracks in the reef framework, created by the grounding of the R/V Columbus Iselin in the Florida Keys, were repaired using limestone boulders stabilized with a tremiepour of concrete and steel bars.71
• Concrete mats were installed to prevent additional loss of reef structure on a groundingsite (Containership Houston) in Florida.43,45
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It is important to note that careful consideration should be given to the substrate material chosenfor restoration of the structural integrity and complexity of a damaged reef The function of anartificial substrate depends on:
1 Its structural characteristics (composition, surface, design, and stability)
2 The environmental characteristics (temperature, light, sediment, surrounding biota,hydrodynamics, depth, and temporal effects)
These factors are discussed in detail in Spieler et al.76
3.2.2.3 Restoring Topographic Complexity
A loss of topographic complexity is often the case following large-vessel groundings,51,54,70,74,77
coral mining,52 blast fishing,72 and major dredging accidents.51 The reestablishment of topographiccomplexity and appropriate substrate on a damaged reef is a major aspect of restoration, as thesefactors affect both coral recruitment and fish abundance.51,78–80 Coral larvae require specific substrateand environmental conditions for settlement (see Petersen and Tollrian81 for references) Surfacesthat have a higher spatial complexity and rugosity are more suitable for recruitment and survival
of biota.74,82–87 Moreover, coral cover is directly related to fish abundance,88–90 and topographiccomplexity shows a positive correlation with reef fish diversity and abundance (see Spieler et al.76
for references) This positive relationship occurs because topographic complexity and epifauna(corals, alcyonarians, sponges, etc.) provide shelter and food resources for reef fish.88,91 Lack ofherbivorous fish may inhibit the recovery of a reef because coral recruits depend upon herbivory
to reduce algal cover.11,79,92,93 In addition, failure to restore topographic complexity on injured,exposed reef areas could lead to exacerbation of damages by other disturbances, such as stormevents.71 Without restoration, structural destruction resulting from major disturbance events canlead to shifts in community structure.14,94–96 Examples of projects where a reef’s topographiccomplexity was reestablished include the following:
• Large boulders were installed atop a cruise ship injury site in Grand Cayman, BritishVirgin Islands67
• Large limestone boulders were installed atop concrete mats to provide stability andtopographic complexity on a grounding site (M/V Houston) in the Florida Keys.43,45
• Concrete modular units were placed in areas where dredging had reduced the topographiccomplexity of the reef in Miami-Dade County, Florida The modular units were installed
to attract epibenthic and cryptic communities that would support fish and invertebrates.51
Selection of a substrate appropriate for coral recruitment is vital when restoring topographiccomplexity.97 The most common materials employed to reestablish three-dimensional relief arelimestone and concrete Researchers have established that limestone and concrete are appropriatematerials for coral recruitment.49,51,74,98–100 When concrete is chosen for a restoration project, appro-priate surface rugosity may be accomplished by:
• The inclusion of rocks in the concrete surface87
• The removal of material from the surface as the concrete sets by applying a high waterspray, chiseling irregular forms in the concrete, drilling holes, etc.87,101
• The addition of material to the concrete surface by spraying additional concrete, addingcoarse sand to cement, or attaching items such as bars, plates, or concrete101,102
• The creation of a layered, brick-and-mortar style structure using rocks and cement87 2073_C003.fm Page 43 Friday, April 7, 2006 4:38 PM
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The potential use of larval attractants to enhance recruitment to a restoration area has been
examined Such attractants include calcium carbonate,103 coralline algae,104,105 bacteria from
coral-line algae,106 red algae,107 and neuropeptides from cnidarians.108,109
Although reef repair techniques provide numerous benefits to enhance recovery, the disadvantages
of these techniques are the intense labor required43,46,61 and the cost of materials and equipment.73,75,110
Coral transplantation was first employed during growth rate studies in the early 1900s111 and is
currently one of the most widely utilized and researched techniques for coral restoration The principal
goal of this restoration technique is to accelerate the damaged reef’s natural recovery rate by bypassing
the coral’s slow-growth, high-mortality life-cycle stage and rapidly improving the impacted reef’s
coral cover, biodiversity, and three-dimensional topographic complexity.20,55,110,112,113 In addition to
restoring coral cover on a damaged reef, the additional benefits of transplantation may include:
1 Immediate enhancement of coral cover and, potentially, coral diversity110
2 Enhancement of coral recruitment to the reef through:
a The introduction of reproductive adult corals,51,110 although whether planulae from
trans-planted corals would potentially recruit to the damaged reef has been questioned114,115
b Asexual reproduction through fragmentation110,112
c The potential for existing transplants to stimulate settlement110
3 Enhancement of survival for locally rare species110
4 Addition of corals to areas that are recruitment limited because of poor larval supply or
high postsettlement larval mortality110
5 Habitat enhancement for other reef-dwelling organisms by providing shelter and
increas-ing habitat complexity54,116–118
6 Enhancement of the aesthetic value of a damaged reef area, which is important for tourism119
Coral transplantation has been attempted in locales around the globe and for every type of coral
reef disturbance Examples of transplantation projects include:
• Avoiding and minimizing impacts from coastal development projects (i.e., transplanting
individual corals or entire portions of a reef) in Hawaii,120–123 Mexico,124 Guam,125
Saipan,126,127 Singapore,128 Japan,129 Tutuila, American Samoa,130 and Palau131
• Avoiding and minimizing coral loss from submarine cable installation and replacement
in Guam132–135
• Avoiding and minimizing coral loss from outfall pipe repairs in Florida136
• Avoiding coral loss in Guam from pollution137
• Rehabilitation of reefs following dynamite fishing in the Philippines,17,138–140 Indonesia,22
and the Solomon Islands118
• Rehabilitation of reefs following coral mining in the Maldive Islands20 and Solomon Islands118
• Rehabilitation of reefs following coral mortality from thermal effluent in Guam34
• Rehabilitation of reefs following mortality caused by sewage pollution in Hawaii44,116
• Attempting to accelerate reef recovery following a submarine grounding (USS Memphis)
in Florida141 and vessel groundings in the Florida Keys43,54,70,74 and Grand Cayman, British
Virgin Islands77
• Rehabilitation of reefs damaged by tourism in Eliat, Israel142
• Enhancement of aesthetics for tourism by transplanting large coral heads into the Gulf
of Aqaba143
• Rehabilitation of reefs damaged by thermal stress and algal blooms in Costa Rica,
Panama, and Colombia13,144,145
• Rehabilitation of reefs damaged by crown-of-thorns starfish146
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Coral branches, colony fragments, entire colonies, and settled planulae may be transplanted.Various techniques for attachment of transplants have been attempted, including epoxy,43,124,126,132,140,147
Portland cement,136 Portland cement mixed with molding plaster,130,148 Portland mortar mix,149 cotta tiles,34,137 plastic wire ties,87,150 rubber-coated wire,116 steel stakes/bars,123,144,150 corrosion-resistanthardware,43 large concrete mats placed over the substrate,20 transplants wedged into crevices,151 andothers
terra-The disadvantages of transplantation include:
1 The intensive labor and cost required (i.e., the extensive time underwater removing andtransporting colonies and the expensive materials and equipment)17,46,110,124,151–153
2 The impacts on donor colonies and populations20,55,110,112,154–157
3 The potential for increased mortality rates in transplants110,112,137,138,140,146
4 The potential for decreased growth rates in transplants20,137,158
5 The potential for dislodgement from the point of attachment due to wave action20,34,137,146,150,159
6 The potential for reduced fecundity of transplants resulting from the stress of removal,transport, and transplantation160
3.2.3.1 Alternative Transplantation Techniques
3.2.3.1.1 Transplantation without Attachment
Because the typical methods of affixing corals to the substrate require extensive labor andexpense, and because the majority of countries that have the greatest need for coral restoration
do not have the resources available for such an endeavor, methods of transplantation that wouldrequire less cost and labor have been examined Some studies have focused on transplantationwithout attachment of the transplanted corals, a method that mimics asexual fragmenta-tion.22,34,55,113,118,137,143–146,150,161,162 The advantage of this technique is that it does not require the use
of SCUBA diving or expensive materials.55 However, unattached fragments could be displacedand/or subject to mortality from storm events or wave action,137,146 and this technique cannot besuccessfully used for high-energy environments.55
3.2.3.1.2 Coral Gardening and Coral Seeding
To minimize impacts to donor corals and populations, alternative sources of transplant materialhave been examined Possible sources include the collection of juveniles from high-risk, extremelyshallow reef environments,163 the collection of fast-growing “weedy” corals that are outcompetingmassive coral colonies,118 and the use of coral “gardening” to supply transplants
Coral “gardening” is the mariculture of corals for use in coral restoration.142,164,165 Theconcept of coral gardening is similar to that of silviculture,165 where coral recruits are raised
in nurseries (in situ or ex situ) and then transplanted to restoration sites.142 Coral gardeningstudies have shown promise for rehabilitating denuded reef areas.142,156,166 The advantage ofthis technique is that it avoids the adverse impacts to donor populations that occur duringdirect coral transplantation.142,156,166,167 In addition, the introduced corals may provide geneticdiversity to the damaged reef area.164 The disadvantages of this technique include the lengthytime frame required to establish a viable nursery capable of supplying transplants167 and the
possibility that corals raised in situ may be impacted and/or destroyed by environmental
disturbances (e.g., storm events, temperature extremes, disease, etc.)
Coral “seeding” has also been proposed as a method of enhancing recruitment for restoration.This technique involves collecting coral larvae from the field, or spawn that has been collected inthe field and cultured in the laboratory, and settling these larvae on reef substrate.166,168–171 Whilethis technique would avoid the damage and removal of healthy donor corals, an efficient andsuccessful methodology has not been developed at this point
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3.2.3.2 Transplantation Questions and Research Needs
Because transplantation is one of the most widely employed and researched restoration techniques,questions and research needs regarding the technique have been noted in the literature Researchersclearly have not ascertained which coral reproductive strategies are most appropriate for specifictransplantation scenarios Some researchers suggest that branching coral species are preferable foruse in transplantation in low-energy areas because they are rapid growers and can quickly increasecoral cover and generate conditions that are favorable for recruits.55,161 Others theorize that slow-growing mounding corals may be more appropriate for transplantation because they are slower torecruit, have longer life spans, and tend to survive severe storm events better than branchingspecies.110,118 Some suggest that the best corals for transplantation are the massive broadcasters,which have a high survival rate once a specific size is reached,172 while others suggest thathermaphroditic brooding corals are appropriate for transplantation techniques.142,173
Although a fair number of coral species have been used for transplantation research andprojects,25 additional research is needed to define the suitability of a particular species for trans-plantation with respect to a variety of environmental conditions (i.e., the effects of depth, waveaction, water quality, season, and substrate on the effectiveness of transplanting a coral species).55
In addition to this, the minimum size of a coral transplant that will allow for a 100% survival ratemust be determined.25 Further research is also needed to ascertain the effects of transplanting coralsinto habitats that are different from the donor site55 and to expand knowledge on transplantmethodology (e.g., species tolerance for transport and transplantation)
3.2.4 A RTIFICIAL R EEFS
In certain situations, restoring the reef via indirect action, reef repair, and/or transplantation is notviable In such cases, the installation of artificial reefs may be considered The general goals of anartificial reef installation in a restoration project are to:76,174,175
1 Mitigate for reefs damaged by anthropogenic activity
2 Alter currents
3 Restrain rubble
4 Restore habitat by providing substrate and refuge for fish, coral, and other reef organisms
5 Conserve biodiversity and enhance the reestablishment of damaged reefs
6 Provide aesthetically pleasing structure(s) for tourism
The goal of an artificial reef installation that concentrates on restoring corals is to establish astable, wave-resistant, fixed substrate that provides refuge, where corals can recruit and/or betransplanted.76 (See Chapter 7.) The refuge provided by such an artificial reef enhances fish andinvertebrate communities.76 The disadvantages of artificial reefs include:
1 The potential for the loss of corals, fish, and other biota by relocation from natural reefs
to the artificial structure46
2 The potential for exacerbation of overfishing on artificial reefs, as they concentratefish46,176
A vast array of items has been utilized to fabricate artificial reefs (e.g., tires, plastic, metal,wood, fiberglass, polyvinyl chloride (PVC), boulders), although the most commonly used materialsfor artificial reef restoration projects are concrete and limestone rock, oftentimes in formed modules.76
(See Chapter 7.) In addition, there has been recent research on the creation of artificial reefs throughelectrolytic precipitation of minerals, Mg(OH)2 (brucite) and CaCO3 (aragonite), onto conductivemetal.177–181 Corals can then be transplanted onto the mineralized structures
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Artificial structures have been employed in a wide array of restoration projects Examples include:
• A derelict vessel was sunk to provide additional habitat and for dive tourism in Rota,Commonwealth of the Northern Mariana Islands (See Chapter 15.)
• Corals and tridacnid clams were transplanted onto hollow, igloo-shaped, stone andcement “fish houses” placed in tide pools on the reef flats in Fiji to enhance fisheriesresources.118
• Limestone boulders and various concrete modules (tetrahedrons, Reef BallsTM, A-JacksTM,and Warren Modules) were deployed as mitigation following the grounding of a subma-
rine (USS Memphis) in Florida.103,141
• Department of Environmental Resources Management (DERM) modules (concrete basewith embedded limestone boulders) were deployed as mitigation following a fiber-opticcable installation in Florida.141
• Limestone boulders were deployed as mitigation following a beach nourishment project
in Florida.141
• Three different concrete modular unit designs were installed off Miami-Dade County,Florida, as mitigation for injuries caused by dredging The modules were designed toenhance habitat for fish and motile invertebrates and provide refuge for associatedorganisms.51,182
• Artificial reefs constructed of PVC plates were installed off Eliat, Israel to relieve divingpressure on natural reefs.183
It is important to carefully consider both the chosen artificial substrate’s structural characteristicsand the environmental factors of the restoration area, as both will work together to determine howthe substrate functions.76 The chosen material could affect the benthic organisms that can inhabitthe substrate.102,184 The substrate’s structural characteristics would include composition, texture,chemistry, color, design, and stability, while the environmental factors to consider would includetemperature, light, sediment, surrounding biota, hydrodynamics, depth, and temporal effects.76 Otheraspects to consider would be cost (construction and labor)76,185 and aesthetic value.76
3.3 COST OF CORAL REEF RESTORATION
One of the most challenging aspects of coral reef restoration is the associated cost, which depends
on a variety of factors, including materials and labor The factors that will affect the cost ofrestoration include the restoration plan’s site location, chosen restoration technique(s), site con-ditions, and the availability of funds.186 Detailed costs for restoration projects are not generallyavailable in the literature.36,186 Spurgeon and Lindahl36 compared the costs of five coral restorationprojects that varied in technique (triage, reef repair, transplantation, and/or artificial reefs) andwere located in four different countries (United States, Maldives, Australia, and Tanzania) Costswere found to vary tremendously between projects, ranging from approximately US$13,000 perhectare for low-tech methods with local labor to more than US$100 million per hectare forextensive restoration work Jokiel and Naughton187 found that many previous restoration projectsmay have been more cost-effective by concentrating on prevention, preservation, and protection
of the resources
Cost is a major factor in the selection of a suitable restoration technique A country’s economicresources will dictate the restoration options that are available Hence, the most expensive andcomprehensive research projects have been conducted in developed countries (United States andJapan)
Decision-making tools may aid with the selection of a course of action (whether or not toproceed with restoration) to determine the best use of available funds.186 Benefit-cost analysisassesses the ratio of benefits to costs for a particular course of action and would assist in the
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selection of the most cost-effective use of funds and maximize the benefits of the chosen path bydeveloping the details of the selected plan.186 Least-cost analysis identifies the most inexpensivemethod for realizing a specific environmental goal.188 Cost-effectiveness analysis may be used toidentify the least and most cost-effective methods for realizing a specific environmental goal whilecomparing various levels of improvement.188,189 Multi-criteria analysis assists with the selection of
a course of action by assigning scores, weights, and priorities to objective criteria without requiringmonetary estimates.190,191 Habitat-equivalency analysis is used to determine the appropriate com-pensation for interim loss of natural resources.192 Refer to Spurgeon and Lindahl36 for a thoroughexplanation of the benefits and disadvantages of these tools
3.4 SUCCESS OF CORAL RESTORATION TECHNIQUES
A definitive definition of coral reef restoration “success” has not yet been developed.14 The majority
of existing restoration projects have been oriented toward mitigative compliance success rather thanfunctional and structural attributes.14 In addition, the overall effectiveness of coral restorationtechniques is not clear, as few studies have carried out thorough monitoring programs over asubstantial time span A quantitative comparison of all reef restoration projects/methods has notyet been conducted Restoration projects to date have varied widely in habitat structure, environ-mental conditions, method, and species examined For these reasons, it is difficult to compare theeffectiveness of restoration projects Nevertheless, we must attempt to collect and utilize theknowledge gained from the projects and research that have been conducted thus far.14
As has been shown to be the case with related sciences such as seagrass and wetland restoration,site selection is key for coral reef restoration projects.110,137,193 Failure to select an appropriate sitecould lead to an unsuccessful restoration project.110,137 As is the case with seagrass restoration, if
a reef has not existed in a particular site over geologic time, there is an underlying reason,37 and
it is therefore not an appropriate site to establish a reef via transplantation or artificial reefs.Additionally, a successful restoration technique must be appropriate for the selected coralspecies,20,140 the environmental conditions of the site, and the economic resources of the country orregion.112 The following sections review the trends in effectiveness for the individual coral reefrestoration techniques
3.4.2 R EEF R EPAIR
Little published experimental or hypothesis-based research has been conducted for reef repairtechniques It has been suggested that reattachment of surviving, dislodged colonies is particularlyimportant in areas where coral recruitment is limited, such as the Caribbean and western Atlantic.195
In addition, we know that failure to restore topographic complexity following a major disturbanceevent can lead to shifts in community structure.14,94–96
As transplantation is one of the most widely used and researched techniques for coral restoration,several trends have emerged with respect to its effectiveness With regard to site selection, it appears