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Review

Coral Reef Restoration Techniques and Management Strategies in the Caribbean and Western Atlantic: A Quantitative Literature Review

by
Leah Hodges
1 and
Pamela Hallock
2,*
1
Honors College, University of South Florida, Tampa, FL 33620, USA
2
College of Marine Science, University of South Florida, St. Petersburg, FL 33701, USA
*
Author to whom correspondence should be addressed.
Diversity 2025, 17(6), 434; https://doi.org/10.3390/d17060434
Submission received: 17 April 2025 / Revised: 4 June 2025 / Accepted: 11 June 2025 / Published: 19 June 2025
(This article belongs to the Special Issue Ecology and Paleoecology of Atlantic and Caribbean Coral Reefs)
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Abstract

:
A quantitative literature review of restoration techniques and supporting management strategies used throughout the Caribbean and Western Atlantic from 1998 through 2024 was compiled using references from the Web of Science to highlight those with potential for reef replenishment. From 93 sources listed, 74 publications were relevant and categorized into subtopics based on the most prevalent restoration techniques. Roughly half the studies focused on three general topics: the benefits of restoring Acropora species, studies utilizing micro-fragmentation and fragment nurseries, and outplanting techniques. Other subtopics, each with at least three references, included optimizing substrates and artificial reefs, enhancing larval recruitment, emphasizing the role of herbivory, improving management practices, and addressing the impacts of tourism and community engagement. The information from the references was compiled to determine the overlap among categories and the ways in which techniques and management strategies might be applied simultaneously to enhance restoration outcomes. Additionally, sources were analyzed according to time and location of publication to better visualize the emergence of this area of research and restoration efforts. An increase in publications was observed from 2014 to 2024, associated with the rise in major events impacting coral reefs. The major locations for published research were the Florida reef tract and Puerto Rico, though restoration studies were also reported from the Bahamas and sites around the Caribbean. Criteria to assess the success of techniques included coral survival, recruitment, coral coverage, habitat structure and complexity, and biomass of marine life, including fish and invertebrates that inhabited a restored reef. Most restoration efforts utilized either fragmentation or assisted sexual breeding, followed by cultivation in nurseries or labs. Outplanting success depended on fragment size, attachment style, and site selection, with less-intrusive techniques and intermediate planting densities promoting survival. Tools like GAO maps can guide site selection based on herbivore presence and algal coverage. Monitoring is critical to ensuring coral survival, especially after the first year of outplanting, while community involvement can foster public engagement in reef conservation.

1. Introduction

Coral reefs are among the most diverse marine ecosystems, supporting a wide range of marine species and providing human communities with a vast array of ecosystem services [1,2,3,4,5,6]. They act as natural offshore barriers, reducing the impact of storms, wave action, and coastal flooding [1,4]. Reefs also support local food security through fisheries and contribute significantly to regional economies via tourism and recreation [2,5,6]. The presence of healthy coral reefs often drives the development of coastal resorts, hotels, and recreational infrastructure, stimulating job creation and economic growth [2,6]. For many island and coastal nations, coral reefs are a cornerstone of economic stability and development. Their ecologic, economic, and protective functions underscore the importance of their conservation and restoration.
Coral reefs can be damaged by a range of stressors, from hurricanes, anomalously warm or cold events, disease outbreaks, effects of destructive fishing and recreational activities, overfishing, pollution, and many other factors [2,3,4,6,7]. As human populations have increased and climate change is causing more stress events, including mass mortalities of corals and associated organisms, scientists and resource managers worldwide are seeking ways to reduce decline and mitigate losses [2,3,7]. Following the unprecedented worldwide mass coral bleachings in 1997–1998 [6,7], efforts to restore damaged and declining coral reefs gained momentum. The research question, as addressed in this review, is the following: “What coral reef restoration techniques have been implemented around the Caribbean and Western Atlantic, and what array of techniques will likely be successful and efficient?”
A review compiling successful techniques and management strategies is essential under the ongoing environmental conditions discussed above. Quantitative literature analysis can be beneficial by summarizing successful trends, gaps in research, and challenges faced in the field, which can contribute to timely implementation [8]. The purpose of a quantitative literature review is to systematically examine and synthesize previous studies to provide efficiency when assessing completed research [8]. Such a review can aid in identifying patterns and trends across research, such as common findings and consistency regarding the implementation of restoration techniques and management strategies. Alternatively, a quantitative literature review can highlight gaps in the literature where evidence may be lacking or inconsistent. The goal is to contribute direction for future research, as well as to improve research design.
A quantitative literature review can be used to quantify research publications on a topic, providing data on progress and research subtopics within a field or subject of interest [9,10]. The purpose of our review was to identify the range of coral reef restoration techniques reported in the literature, specifically in western Atlantic and Caribbean sites and found on the chosen database, Web of Science, published between 1998 and late 2024, to identify those indicating the potential for replenishing coral reefs. Success can be measured as the rate of coral survival, rate of recruitment, coral coverage, habitat structure and complexity, and biomass of marine life, including fish and invertebrates, inhabiting a reef. The goal was to identify the restoration approaches that can be applied individually, sequentially, or simultaneously to enhance restoration outcomes. Informing researchers of previous methods and findings can contribute to the design of future studies with improvements focused on areas of inconsistency or lacking research.

2. Methods

This review was based on publications listed on the Web of Science (www.webofscience.com, accessed between 1 October 2024 through 1 April 2024) using the search terms “reef restoration Caribbean” and “reef restoration Western Atlantic”. The Web of Science was the chosen database as it tends to identify specific sources based on the titles and keywords rather than including articles that identified the search terms somewhere, including in the references [11]. The Web of Science is a widely used scientific database that offers a broad range of documents for more in-depth analyses, including peer-reviewed articles, book chapters, theses, dissertations, non-peer-reviewed papers, and short communications [11]. The search using “Caribbean” produced 88 references, while the search using “Western Atlantic” provided 11 sources, only five of which were unique. Variability was observed in search results during the study, as the same search term sometimes produced different numbers of sources. The search that generated the largest pool of references was utilized. From the resulting 93 sources, 74 publications were categorized into subtopics based on the most prevalent restoration techniques. The other 19 sources were either unrelated to the research topic or focused on a location outside of the Caribbean or Western Atlantic. The search terms, including both the Caribbean and Western Atlantic, were able to pull sources from the entirety of the Caribbean, including Latin American territories. The compiled sources from the chosen database provided the information reported in this review. While additional supporting sources may be pulled from other databases, the review was focused on findings listed in the Web of Science based on the search terms. The data reported in this review do not account for unpublished work that may have resulted in little to no success.
The sources were compiled into an Excel file to easily categorize the location and date of publication, main contributors, affiliations of contributors, and restoration technique discussed. The results were used to create a chart to show the number of publications associated with each restoration category and a map of the research locations where the studies were carried out. A timeline of major events impacting reefs in the region (e.g., hurricanes, cold events, and disease outbreaks) was compiled. Finally, the resulting information was summarized into a flow chart to visualize successful techniques and their possible implementation along with other approaches to reef restoration.
There are several caveats and limitations to the targeted quantitative review approach, which is also known as scientometric review [11]. In the case of this study, coral restoration methods are consistently improving over time, though survivorship of restored corals is difficult to assess because environmental stressors are numerous and also continuously changing. Given this, the review compiles the overall successful techniques reported in the targeted source. Mortality related to acute warming or cooling of the ambient ocean temperatures may contradict the findings, as these stressors are out of the control of restoration efforts to mitigate. Rather than focusing on the possibilities surrounding these detrimental issues, the paper concludes by summarizing the techniques that document success and, thus, the possibility of survival in light of the current environmental threats. The specific goal of the study was to compile the defined range of papers to provide reef-restoration practitioners with a list of references and a summary of reported successful approaches published in the first quarter of the present century.

3. Results

This review identified 74 papers dealing with reef restoration in the Western Atlantic and Caribbean between 1998 and 2024, with more than a third published after 2020 (Figure 1).
The 74 publications identified were categorized into subtopics based on the most prevalent restoration techniques (Figure 2a). Roughly half the studies focused on three general topics: the benefits of restoring Acropora species, studies utilizing micro-fragmentation and fragment nurseries, and outplanting techniques. Other topics explored included optimizing substrates and artificial reefs, enhancing larval recruitment, emphasizing the role of herbivory, improving management practices, and addressing the impacts of tourism and community engagement. The findings of these studies are further presented below, by category in chronological order of how they could be applied in the field, accounting for the interrelatedness of the techniques. The locations around the Caribbean and Western Atlantic where these studies were carried out are shown in Figure 2b. While the Florida reef tract and Puerto Rico predominated, other restoration studies were reported from the Bahamas and a diversity of sites around the Caribbean.

3.1. Benefits of Acropora

Species of Acropora, especially Acropora cervicornis, were the most common subject for restoration efforts. While the majority of studies utilized a species of Acropora, the 17 chosen specifically discussed the benefits of efforts to restore these species. Many others simply explained the subject matter without noting the benefits of restoring Acropora species. Because A. cervicornis is listed as critically endangered under the Endangered Species Act, CITES, and the IUCN Red List, it is a focal candidate for restoration initiatives [12,13,14,15,16]. Adult colonies can be fragmented up to 75% without significant damage [16], and fragments have exhibited high survivorship in nurseries [17,18]. Outplanted fragments also have high survivorship [14,16,17], with equal to or higher growth rates than wild A. cervicornis [19].
Several studies found that survivorship of fragments in both nurseries and outplant locations surpassed 70% annually. One study found that live coral tissue of A. cervicornis did not persist past two years of outplanting [20]. However, this was an outlier among the many studies that demonstrated survival over a period of five or more years. Moreover, that report was for outplanting along the Florida reef tract at higher latitudes than many other restoration sites. Florida reefs are subject to more intense stressors, including rapid temperature changes across varying seasons and human-inflicted damage such as boating or diving incidents, overfishing, and pollution runoff. Alternatively, the study [20] may appear to be an outlier because most research with negative results has remained unpublished.
Acropora cervicornis is known for having rapid growth rates, which benefits restoration initiatives and enhances the rate at which reefs can be restored [17,21]. They demonstrate high physiological plasticity through forming associations with many different strains of Symbiodinium “fitti” within Clade A, increasing thermal tolerance and promoting higher symbiont diversity [22]. In addition to the benefits of A. cervicornis as a subject for restoration projects, their branching morphologies provide ecological and functional importance, including predator deterrent for adjacent vulnerable corals [15], increase and attract larval recruitment by at least 2.21 times [23], and, in dense aggregations, promote higher fish biomass [17,24].
An implication to consider involves reports from fieldwork completed in 1974 and 1976 that found virtually no Acropora recruitment [25,26]. While Acropora species may not recruit well in the wild, they have proven recruitment success within laboratory facilities via assisted sexual reproduction, as described further in this review [27,28,29]. Additionally, these species often have relatively high survival rates following fragmentation.
While Acropora have been the primary taxa in restoration projects in the region considered, other techniques and management strategies listed in the review do not necessarily pertain to only Acropora species. The genus Acropora tends to be found in relatively shallow waters with higher wave action and is not suitable for restoring intermediate and deep reefs [13,14]. The purpose of the review is to provide an overall summary of findings and successes that may involve the use of other species, which are mentioned throughout the paper as they apply.

3.2. Micro-Fragmentation and Nurseries

Asexual reproduction by fragmentation of branching corals (primarily Acropora spp.) has long been recognized as an important recovery response to physical damage by storms. Thus, the fragmentation of donor corals can be efficient in restoring degraded reefs rapidly at a low cost [30]. Up to 75% of coral tissue can be propagated from A. cervicornis [31] and up to 12% from A. palmata without detrimental effects on the growth and reproduction of the fragments and donor colonies [32,33]. Some researchers have reported that larger fragments grow faster [13], while other researchers suggest that smaller initial fragments show accelerated growth rates [33,34]. The use of smaller fragments reduces damage to parent colonies, but the fragments may be more susceptible to mortality during handling and transportation [33]. Additionally, faster-growing fragments may sacrifice skeletal density and be more susceptible to breakage [35].
The use of coral nurseries has proven to be an efficient restoration approach since the growth rates of fragments in the nurseries can exceed those of wild colonies [33,36]. The most efficient and cost-effective nursery designs were line nurseries in which the coral fragments remained suspended, providing high survival, growth, and productivity rates, with minimal upkeep required [18,37,38]. Floating lines, horizontal frames, and tree nurseries are the most common types of line nurseries implemented in the field [39]. Line nurseries can remain self-sufficient for several months without suffering the effects of biofouling, temperature variations, or hurricanes, especially when placed in slightly deeper locations distant from shallow reefs [38,40,41]. Other effective nurseries to consider are benthic attached A-frames and benthic blocks. However, while still effective, they are subject to more algal growth and biofouling than the line nurseries [42]. Additionally, colonies grew three times faster in line nurseries than benthic-attached nurseries, which were also more prone to bleaching first; however, they survived longer than the colonies in line nurseries once bleached [42]. Nurseries not only provide a secondary habitat on degraded reefs but also allow for close monitoring of coral health, enhanced sexual selection through close dispersion of gametes, uptake of beneficial endosymbionts from neighboring corals, and provide a sustainable bank of corals to use for research [21,36,43,44]. When properly managed and located in marine-protected areas, the corals face fewer threats from environmental pressures, predators, and algal competition [36,45]. Hurricanes and strong storms are damaging to reefs and cause breakage of corals, though storm-generated A. palmata fragments can be rescued for rehabilitation in nurseries, with the probability of survival increasing with larger fragments [46].

3.3. Genetics and Selective Breeding

Selective breeding, or assisted sexual reproduction, within a laboratory, can mix genotypes to enhance genetic diversity [47,48,49]. Higher genetic diversity within coral species is positively correlated with disease resistance and thermal tolerance. Genetic grafting can be used to understand the genotypic diversity of coral fragments, given limited resources [50]. Genetic grafting, which involves bundling various fragments together and taking note of fusing between genetically similar fragments, can be completed almost anywhere. Tracking the genotypic diversity of fragments is beneficial for restoration techniques as it quantifies diversity and allows genetically diverse fragments to be used, improving the diversity of a reef. Among wild colonies of A. cervicornis, there is low genetic diversity and variability within dense banks, but more genetic differences occur between banks [16]. Diversity among A. cervicornis thickets is vital for surviving environmental stressors or disease and strengthening restoration efforts; thus, outplanting genetically diverse colonies provides a higher potential for success.
While the majority of studies report work with Acropora spp., efforts with other species have reported similar trends. For example, hermaphroditic brooder corals had high reproductive output and displayed resilience and high survivorship two years after outplanting [51].

3.4. Acclimating Corals to Enhance Resilience

Pre-exposure to higher temperatures during the early stages of life can promote higher thermal tolerance during heat-stress events [44]. The acute Coral Bleaching Automated Stress System (CBASS) is a cost-effective tool that can be used in tanks to mimic the warming patterns within the oceans [52]. This device can also be used as a rapid screening tool for detecting the tolerant genets to breed and outplant for restoration interventions. Targeting thermally tolerant individuals for sexual propagation or breeding can increase to the overall survival rates of the selected gene pool during heat-stress events [47,49]. Damaged corals from warmer reefs exhibited faster rates of recovery during heat stress than corals from cooler reefs [53]. These results emphasize the importance of sourcing fragments from warming environments and outplanting them into cooler environments that may experience increasing temperatures in the future.
Additionally, rearing juvenile Orbicella near adults of other species containing thermally tolerant endosymbionts of the genus Durusdinium enhanced the uptake of the endosymbionts and increased tolerance during heat stress [44,54].

3.5. Outplanting Techniques

Outplanting coral fragments in degraded reefs can restore habitat and ecosystem function if coral stressors can be managed and the mortality of outplanted fragments is low. The first small-scale transplanting in 1999 used storm-generated fragments as an inexpensive method and limited harm to donor colonies but resulted in high mortality [55]. A significant percentage of mortality in outplants resulted from dislodgement (56%), which has been resolved in more recent restoration efforts. Recent outplanting techniques have facilitated survival rates, with one study reporting >70% after 12 months [36]. The highest rates of success resulted from outplanting larger fragments and using nails and cable ties for attachment [14,56]. According to the study completed by Goergen and Gilliam, outplanting A. cervicornis in lower densities had higher survival rates and lower rates of disease, predation, and missing colonies [56]. Ware et al. found that dense clusters of small fragments had a higher probability of survival than large fragments planted individually [57]. In one case, different findings are associated with the size of the corals outplanted [58]. When outplanting larger fragments, which have higher survival rates during the transportation and handling processes, it is best to plant in lower-density plots [56]. Alternatively, when utilizing smaller fragments, higher survivorship was found upon outplanting in dense clusters [58]. Planting corals at intermediate densities may perform the best for all fragment sizes, as an increase in habitat production was found at a density of three corals per m2, with a negative impact at higher densities [57]. Outplanting coral juveniles on clay tiles directly after recruitment might be useful in restoration since this technique is less expensive than nurseries and has shown higher survival rates than nursery-raised recruits [59]. A limitation to this process is that if the juvenile corals are not closely monitored during their early stages of life, they are more susceptible to predation, suffocation from sedimentation, and the spread of diseases.
Degraded reefs that once supported dense coral populations, as well as marine-protected areas containing shallow reefs, have been associated with increased survival and productivity rates [20,60,61]. Global Airborne Observatory-derived (GAO) maps were used to locate suitable reefs for outplanting: preferred characteristics included 3–7 m in depth, high rugosity, and low macroalgal cover [62]. Corals outplanted on the chosen reefs had a survival rate of 92% after three months and 76% after a year.
Outplanting efforts to restore reefs faster than the rate of degradation must be proportional to the size of the existing coral populations and conditions on a reef. An increase in stressors, such as predation, may require an increase in the threshold to restore the population at a faster rate than degradation. Predation was one of the leading causes of mortality among recent Orbicella faveolata outplants and juvenile recruits in Puerto Rico, so acclimation cages were used to mitigate this issue [63]. Non-branching species face more risk of predation because they lack a naturally defensive growth structure. Adult Acropora spp. do not often face predation. However, juveniles and recruits are more susceptible as they lack sufficient branching to serve as a defense against predators. The dense branching form of A. cervicornis serves as a predator deterrent and protects vulnerable adjacent corals, such as juveniles and non-branching species, which can be beneficial when choosing outplanting locations [23]. Newer outplants are more vulnerable than older and non-transplanted individuals, so close monitoring within the first year is critical to ensure that habitats are suitable [64]. Major stressors for new outplants include predation, disease, and bleaching.

3.6. Substrates and Artificial Reefs

Artificial reefs can enhance biodiversity in an ecosystem by attracting marine life from surrounding reefs, but both fish and benthic assemblages remain distinctly different from natural ecosystems [65]. In comparing the performance of artificial reef structures to natural reefs, specifically in relation to benthic assemblages (e.g., macroalgae, cyanobacteria, crustose coralline algae, coral recruits), artificial reefs shifted to more cyanobacterial turfs and macroalgae, which inhibited the settlement of coral larvae and increased competition for adults [66]. To promote coral settlement, a calcium-carbonate inducer can be added to the substrate to mimic crustose coralline algae and attract coral larvae [67]. In high concentrations, calcium-carbonate treatment can be toxic and reduce the growth rate of the corals, so it is critical to incorporate appropriate quantities. Settlement and survival were tested on both rugose and smooth surfaces, with no significant difference in larval settlement but a significantly higher survival rate on smooth surfaces [68]. Substrates tested with various coatings to examine larval recruitment revealed that the combination of high water repellency and phosphorescence-based color increased recruitment of Orbicella spp., although survival on all substrates was low [69]. In addition, artificial reefs can have negative effects by leaking chemicals, such as silicates and ferric ions, into the water column, thereby altering the chemical balance of the seawater [66,67]. In addition, many artificial reefs are accessible to fishers, and because fish populations move between natural and artificial reefs, unregulated fishing can lead to the depletion of stocks in both habitats [66].

3.7. Increasing Larval Recruitment

Recruitment of coral larvae is critical for restoring degraded reefs. By comparing regional differences in coral recruitment rates with predicted future recovery, higher larval dispersion and recruitment indicated faster recovery after stress events, while areas of lower recruitment may delay recovery for many decades [70]. As noted previously, coral settlement can be induced onto smooth substrates treated with calcium carbonate, as recruits respond similarly as they do to crustose coralline algae, a common settlement substrate favored by recruits in the wild [71]. The substrates release natural biochemical cues that attract settlers and increase settlement rates. One land-based study found a significant preference by A. cervicornis for biologically conditioned, top-oriented, rugose substrates [72], while a later study reported that larval survival was reduced as a result of sediment accumulation and turf-algal growth on rugose surfaces [68]. Coral larvae do not tend to grow and mature under stressful conditions because they require high-energy resources to survive.
A study that tested larval recruitment on natural substrates in the presence and absence of A. cervicornis found higher recruitment levels on substrates containing an A. cervicornis adult [15]. Larvae use cues to identify suitable substrates, which may include the presence of another healthy coral. To strengthen restoration initiatives, it is critical to utilize the connectivity of reefs, specifically within highly connected systems such as the Florida Reef Tract [73]. Understanding the connectivity and currents of a reef system can boost larval dispersion and aid in creating marine protected areas to maximize restoration efforts and efficiently restore degraded reefs.

3.8. Macroalgal Cover and Herbivore Abundance

Benthic algae are major competitors for substrates in a coral reef ecosystem. In the presence of dominant herbivores (fish and invertebrates), macroalgal cover can remain in check, allowing corals the space to recruit and grow [74]. In the absence of herbivores, macroalgal abundance can increase and outcompete the corals for substrate on the reef. Maintaining invertebrates and herbivores in nursery facilities can reduce algal growth and labor needed to remove the algae, enhancing the survival of corals [75]. Grazing on reefs is enhanced by rugosity, which provides a complex habitat structure for herbivores to hide from predators, increasing the proportion of urchins and decreasing macroalgal cover [76].
Diadema antillarum urchins are key grazers on reefs but often become clustered together, forming dense colonies. Evenly distributing their populations over a large area of reef showed a decrease in macroalgal cover due to increasing grazing rates of individual urchins, though the process was not always successful [77,78]. Alternatively, D. antillarum can also be cultured in a lab facility and outplanted to increase their populations in reef environments. Those cultured in a non-rugose environment did not display crevice-seeking behaviors or escape behaviors that are exhibited by wild specimens and also developed lower spine densities [79]. Differences from wild specimens are reduced by providing rugose habitat in culture, resulting in more ecologically competent individuals that emulate wild populations when released on reefs. Additionally, providing shelter for the herbivores can reduce predation, increase the abundance of grazers, and, ultimately, lead to a decline in algal coverage [80].
A concern regarding the introduction of D. antillarum is the possibility of another major disease outbreak, such as the 1983–1984 urchin disease, which wiped out over 95% of the population across the Caribbean [81]. Diadema antillarum individuals that died after the disease outbreak did not match the patterns of the disease, indicating that the outbreak may have been caused by a waterborne pathogen [82]. While D. antillarum is beneficial in reducing algal growth and mitigating competition for corals, their susceptibility to diseases must be understood when considering approaches to support reef recovery.
Alternatively, damselfish, which creates lesions on corals to farm macroalgae, is pervasive on reefs and increases the death rate of corals through increasing susceptibility to disease, algae growth, and bleaching [83]. If coral abundance is restored and restoration efforts successful, healthy reefs can naturally overcome the negative effects of damselfish.

3.9. Increased Management and Government Regulations

Lack of management in field locations for extensive periods of time, as observed during COVID-19, can result in negative impacts on coral nurseries and outplant sites [38]. Disease, overfishing, and climate stressors reduce the resilience of corals and lead to the depletion of coral assemblages on reefs [84]. For restoration efforts to be successful, management of water quality and overfishing, as well as the application of ecological engineering/sustainable projects and establishment of more Marine Protected Areas (MPAs), are essential. Artificial reefs can easily become depleted of fish stock through overfishing, so it is critical that they are also monitored and included in management plans [65].
Reef management at a local level is highly dependent on the intensity and frequency of hurricanes [85]. A model was designed to show the relationships of multiple stressors on a reef, including macroalgal cover, herbivore abundance, rugosity/complexity, hurricane impacts, and levels of fishing with hurricane frequency. The simulations demonstrated various scenarios of stressors to develop appropriate management policies for reef restoration and fisheries. Fishing regulations must be strictly enforced at lower hurricane frequencies, while more restoration initiatives are required at higher hurricane frequencies due to physical damage. The abundance of corals can be assessed by colony ellipsoid-volume estimations, which provide guidance for reef managers to better quantify partial mortality and location-specific regression, enhancing the identification of areas of higher mortality [86]. Monitoring and assessing the genetic diversity of corals can also be achieved through generalized estimates based on the published literature, providing reef managers with the minimum number of donor colonies needed to retain genetic diversity in a reef ecosystem [87].

3.10. Tourism and Community Engagement

Incorporating science-based protection and restoration activities into resort operations and other aspects of tourism, as well as the involvement of local communities, can promote reef restoration efforts [88]. Collaboration with the tourism sector, employing its resources and manpower, can contribute to restoration efforts and allow visitors to develop an appreciation for the coral reefs to which they contributed. Encouraging science-based restoration in academia, local communities, and governments can be useful in expanding restoration initiatives. “Rescue a Reef” is a program that trains local citizens and volunteers in propagation and transplantation efforts, which acts as a cost-effective method while promoting community involvement [89]. The project did not harm coral survival or productivity but instead improved knowledge and education within local communities on coral health and reef restoration.
Societal factors are also essential to reef restoration efforts. Language differences among countries throughout the Caribbean and Western Atlantic can impede regional restoration efforts [30]. Increasing involvement within communities and expanding the inclusivity of scientists in the field of research can minimize language barriers. Additionally, the media can be a tool for applying the protection-motivation theory and boosting emotional and behavioral actions in response to fear-appealing videos on declining coral reef health [90]. Videos that presented a serious issue followed by positivity and hope led to an increase in donations, especially among people who have previously visited a reef and could relate the issues to their experiences.

4. Discussion

Events impacting Western Atlantic and Caribbean reefs began to be observed and reported starting in the 1970s (Figure 3). The first incidences of coral bleaching were reported in the Florida Reef Tract in the 1970s by researchers from the Florida Fish and Wildlife Research Institute [91]. Early reports of diseases, specifically Black Band and White Band, were also from the 1970s [92]. The first major widespread coral-bleaching event occurred in 1982–1983, during a major ENSO event that followed the El Chichon massive volcanic eruption in 1982. That was closely followed in 1983–1984 by the Diadema die off around the Caribbean and Western Atlantic [93,94]. New diseases or disease outbreaks were subsequently reported most years through the 1980s and 1990s, with major bleaching events occurring in 1987 and the most massive worldwide bleaching event in 1997–1998 [3,4]. New observations reported with every International Coral Reef Symposium and other regional meetings kept research focused on documenting the decline of reefs, but the 1997–1998 global event triggered interest in efforts to reduce reef decline and initiate efforts at reef restoration. The results have been the surge of studies and publications in the 21st century. The major surge in publications beginning in 2021 likely reflects both the real increase in reef restoration efforts between 2010 and 2020, with the COVID-19 pandemic restrictions limiting access to fieldwork and thereby providing research teams with more time to analyze and document the results they had found in the previous decade.
A timeline of major events impacting coral reefs around the Caribbean (Figure 3) was created to compare with the timing of the increase in publications on reef restoration (see Figure 1). The timeline is color coordinated to relate the major events with the restoration techniques to which they most closely correspond, with the exception of the cold front. The disease with the highest impact is Stony Coral Tissue Loss Disease, which was first observed in 2014, the same year that the notable increase in the number of publications began. Number of publications also spiked during the years of the third and fourth global mass-coral bleachings. Overall, the increase in publications from 2014 until 2024 is associated with the rise in major events impacting the coral reefs.
A summary of restoration approaches deemed successful in the articles reviewed was assembled as a flow chart (Figure 4). Techniques that yielded positive survival and productivity rates were included in the diagram and connected to the recommended application of multiple techniques throughout the restoration process. Sources cited in the text were augmented specifically by information from several other references [101,102,103,104,105,106]. This visual may be useful when designing and managing restoration initiatives to restore degraded reefs. It compiles the information into a flowchart with various paths depending on the method of restoration implemented.
The preferred coral species among the research papers, as indicated by the benefits mentioned in the Section 3.1, forms the base of the flow chart. While it is the most common genus among restoration efforts in the Caribbean, other taxa have been successful when implementing the featured techniques, which is beneficial in enhancing the overall diversity within the reefs. The chart then presents the two methods for acquiring the necessary numbers of the chosen species: fragmentation of an adult species or assisted sexual recruitment through selective breeding of favored genotypes. Coral nurseries are frequently used to cultivate the fragments until they are ready to be replanted on the reef. Alternatively, the lab-bred corals can be provided with smooth tiles, which are treated with calcium carbonate to imitate crustose coralline algae, a favored substratum for recruitment among recruits in the wild [29]. The coral recruits are able to settle on the provided tiles before being outplanted directly or are kept in the lab for the first few years to enhance survival prior to outplanting. The outplanting techniques consider the size of the fragments, the specific location for outplanting, and the attachment style. Unless coral settlers are outplanted immediately, it is generally more effective to wait until fragments grow larger, as this increases their chances of surviving the transport and attachment process. The least intrusive attachment style uses a nail and cable tie to avoid damaging the coral tissue and allow the coral to continue to grow without restricting growth or development. Planting in intermediate densities provides optimal space for all coral-fragment sizes to grow without risking competition between individuals. Whether searching for a healthy reef with favorable conditions, a plot on the reef with healthy corals or predator deterrents, or a highly connected reef system in a marine protected area to promote diversity within the entire system, the location is crucial to allowing the corals the highest chance of survival. Global Airborne Observatory-derived (GAO) maps can be used to identify suitable reefs for outplanting, which considers the overall macroalgal coverage and abundance of herbivores within the area. Culturing and increasing herbivore populations on a reef helps to minimize algal growth and reduce competition for space with coral colonies. The first year after outplanting is the most important period to monitor coral survival and general health. At the local level, monitoring can be carried out to preserve resources, inform residents and tourists about the value of reef restoration, and establish opportunities for citizen scientist participation. Such involvement within the community allows individuals with little to no experience to participate and make an impact on the survival of coral reefs.
While Figure 4 provides a flow chart suggesting the implementation of successful techniques found throughout this quantitative literature review, continued research on all aspects of restoration is essential in light of constantly changing environmental conditions. There are contradictory findings mentioned throughout the paper, demonstrating the limitations of a singular path for restoration initiatives. Instead, the purpose of the diagram is to summarize techniques and ways in which they overlap to enhance coral survivorship. This chart might also help researchers identify overlooked areas of study and guide future efforts to advance the success of coral restoration.

Limitations of the Findings of This Study

This study focused on coral-restoration studies carried out in the Western Atlantic and Caribbean that were identified from a specific subset of the literature. Those criteria largely defined the scope and limitations of this study. An earlier, more extensive review that was global in scope [107] was unfortunately missed and provides an example of the challenges and limitations of a quantitative (scientometric) review. A previous such review of an unrelated topic [11] reported huge differences in quantitative results, depending upon the search engine used, based on the differences in what and how they search. The search results from the Web of Science demonstrated a key misunderstanding in manuscript preparation. A useful strategy in creating the title and keywords for a manuscript has been articulated by Lindsay [108], in which he stated that the goals of a title are to attract readers and guide search engines. He recommended choosing 10–12 key nouns, ranking them in order of importance, and constructing the title using the most important words when possible. The remaining words should be used as Keywords. Many papers simply repeat words that are already in the title, thereby limiting the potential audience.

5. Conclusions

This review compiled publications that document coral restoration techniques that have been implemented throughout the Caribbean and Western Atlantic. Techniques that yielded success and meaningful growth rates among corals were highlighted. The review also notes techniques that were not beneficial or that impacted corals negatively, which should be avoided when planning restoration projects. The increase in publications observed, specifically from 2014 until the present, reflects the increase in major events that have impacted reefs throughout the Caribbean and Western Atlantic. The publications were sorted into categories that highlighted specific techniques, with the most reported being (a) the benefits of using Acropora species, (b) micro-fragmentation and nurseries, and (c) outplanting. These techniques are widely used throughout the Caribbean and Western Atlantic due to their efficiency in restoring degraded reefs while being accessible and cost effective. The less studied techniques were either not as practical in certain locations, required more extensive research tools, or did not prove to be as effective in restoring coral reefs. The main purpose of conducting the quantitative literature review was to gather information from publications regarding coral restoration with the goal of providing facilities that are designing restoration projects with information that might enhance those initiatives.

Author Contributions

Conceptualization, L.H. and P.H.; methodology, L.H.; investigation, L.H.; writing—original draft preparation, L.H.; writing—review and editing, L.H. and P.H. All authors have read and agreed to the published version of the manuscript.

Funding

L.H. expresses her gratitude to the Judy Genshaft Honors College and the USF Green and Gold Presidential Scholarship. This research received no additional funding.

Data Availability Statement

All data used in this manuscript were based on publications listed in the Web of Science (www.webofscience.com) using the search terms “reef restoration Caribbean” and “reef restoration Western Atlantic”.

Acknowledgments

We thank Sam Appiah in the USF School of Geosciences for his assistance in creating the map figure included in this paper. Chantele Bégin at USF and two anonymous reviewers are thanked for providing recommendations that improved the manuscript.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Number of publications identified from Web of Science that dealt with reef restoration in the Western Atlantic and Caribbean between 2001 and 2024. The graph excluded sources that were not relevant to the research topic or dealt with locations outside of the Atlantic Caribbean location.
Figure 1. Number of publications identified from Web of Science that dealt with reef restoration in the Western Atlantic and Caribbean between 2001 and 2024. The graph excluded sources that were not relevant to the research topic or dealt with locations outside of the Atlantic Caribbean location.
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Figure 2. Coral restoration studies found in a Web of Science search of “reef restoration Caribbean” and “reef restoration Western Atlantic”: (a) major topics of the studies found; (b) locations of field or lab facilities of studies [note that the site colors correspond to search categories shown in (a)].
Figure 2. Coral restoration studies found in a Web of Science search of “reef restoration Caribbean” and “reef restoration Western Atlantic”: (a) major topics of the studies found; (b) locations of field or lab facilities of studies [note that the site colors correspond to search categories shown in (a)].
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Figure 3. A timeline of major events impacting coral reefs around the Caribbean, including disease outbreaks, mass coral bleachings, cold fronts, and major hurricanes [3,4,81,82,92,93,94,95,96,97,98,99,100].
Figure 3. A timeline of major events impacting coral reefs around the Caribbean, including disease outbreaks, mass coral bleachings, cold fronts, and major hurricanes [3,4,81,82,92,93,94,95,96,97,98,99,100].
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Figure 4. Restoration initiatives and management strategies considered useful by the researched sources, organized into a flow chart as they might be applied in the field.
Figure 4. Restoration initiatives and management strategies considered useful by the researched sources, organized into a flow chart as they might be applied in the field.
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Hodges, L.; Hallock, P. Coral Reef Restoration Techniques and Management Strategies in the Caribbean and Western Atlantic: A Quantitative Literature Review. Diversity 2025, 17, 434. https://doi.org/10.3390/d17060434

AMA Style

Hodges L, Hallock P. Coral Reef Restoration Techniques and Management Strategies in the Caribbean and Western Atlantic: A Quantitative Literature Review. Diversity. 2025; 17(6):434. https://doi.org/10.3390/d17060434

Chicago/Turabian Style

Hodges, Leah, and Pamela Hallock. 2025. "Coral Reef Restoration Techniques and Management Strategies in the Caribbean and Western Atlantic: A Quantitative Literature Review" Diversity 17, no. 6: 434. https://doi.org/10.3390/d17060434

APA Style

Hodges, L., & Hallock, P. (2025). Coral Reef Restoration Techniques and Management Strategies in the Caribbean and Western Atlantic: A Quantitative Literature Review. Diversity, 17(6), 434. https://doi.org/10.3390/d17060434

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