Coral Restoration Research Articles

Applying coral breeding to reef restoration: best practices, knowledge gaps, and priority actions in a rapidly‐evolving field

Reversing coral reef decline requires reducing environmental threats while actively restoring reef ecological structure and function. A promising restoration approach uses coral breeding to boost natural recruitment and repopulate reefs with genetically diverse coral communities. Recent advances in predicting spawning, capturing spawn, culturing larvae, and rearing settlers have enabled the successful propagation, settlement, and outplanting of coral offspring in all of the world's major reef regions. Nevertheless, breeding efforts frequently yield low survival, reflecting the type III survivorship curve of corals and poor condition of most reefs targeted for restoration. Furthermore, coral breeding programs are still limited in spatial scale and species diversity. Here, we highlight four priority areas for research and cooperative innovation to increase the effectiveness and scale of coral breeding in restoration: (1) expanding the number of restoration sites and species, (2) improving broodstock selection to maximize the genetic diversity and adaptive capacity of restored populations, (3) enhancing culture conditions to improve offspring health before and after outplanting, and (4) scaling up infrastructure and technologies for large‐scale coral breeding and restoration. Prioritizing efforts in these four areas will enable practitioners to address reef decline at relevant ecological scales, re‐establish self‐sustaining coral populations, and ensure the long‐term success of restoration interventions. Overall, we aim to guide the coral restoration community toward actions and opportunities that can yield rapid technical advances in larval rearing and coral breeding, foster interdisciplinary collaborations, and ultimately achieve the ecological restoration of coral reefs.

The potential for coral reef restoration to mitigate coastal flooding as sea levels rise

The ability of reefs to protect coastlines from storm-driven flooding hinges on their capacity to keep pace with sea-level rise. Here, we show how and whether coral restoration could achieve the often-cited goal of reversing the impacts of coral-reef degradation to preserve this essential function. We combined coral-growth measurements and carbonate-budget assessments of reef-accretion potential at Buck Island Reef, U.S. Virgin Islands, with hydrodynamic modeling to quantify future coastal flooding under various coral-restoration, sea-level rise, and storm scenarios. Our results provide guidance on how restoration of Acropora palmata, if successful, could mitigate the most extreme impacts of coastal flooding by reversing projected trajectories of reef erosion and allowing reefs to keep pace with the ~0.5 m of sea-level rise expected by 2100 with moderate carbon-emissions reductions. This highlights the potential long-term benefits of pursuing coral-reef restoration alongside climate-change mitigation to support the persistence of essential coral-reef ecosystem services.

Acropora CervicornisData Coordination Hub, an Open Access Database for Evaluating Genet Performance

Once one of the predominant reef-building corals in the region,Acropora cervicornisis now a focal species of coral restoration efforts in Florida and the western Caribbean. Scientists and restoration practitioners have been independently collecting phenotypic data on genets ofA. cervicornisgrown in restoration nurseries. While these data are important for understanding the intraspecific response to varying environmental conditions, and thus the potential genetic contribution to phenotypic variation, in isolation these observations are of limited use for large-scale, multi- institution restoration efforts that are becoming increasingly necessary. Here, we present theAcropora cervicornisData Coordination Hub, a web-accessible relational database to align disparate datasets to compare genet-specific performance. In this data descriptor, we release data for 248 genets evaluated across 38 separate traits. We present a framework to align datasets with the ultimate goal of facilitating informed, data-driven restoration throughout the Caribbean.

Implementing a transformative approach to the coral reefs' recovery phase

Mitigation and rehabilitation are responses to climate change and human misuse. However, many regions worldwide still lose coral reefs even after implementing these responses. We chose Hurghada city, on the Red Sea, and Weizhou island, on the South China Sea, as sample regions to assess their various modes of coral community structure loss against the combined climatic and human impact drivers that led to this shift. Despite the former being considered a regional coral refuge, while the latter was limited, both regions have previously intervened with coral restoration. We found that even after three decades of impact cessation by forcing laws, most coral reef states are still declining (about a third and a half in both cities), have not harnessed the existing crowded larval density, and are unrecovered. Such findings imply that the combined impacts will persist, necessitating a broad connectivity analysis that enables a suitable intervention (hybrid solutions hypothesis).Each state of coral categories was connected to certain combined stressor factors using our broad connectivity analysis to grasp the extent and relative contribution of coral community shift since our data obtained from comparable sites were widely varied. Moreover, destructive emerged changes have transformed the coral community structure under the forced adaptation scenario of the community structure, boosting those who can resist at the expense of others.To prove our hypothesis, we used the connectivity findings in determining the optimal technique and spots for coral rehabilitation around the two cities. We then compared our findings with the outcomes of two other existing adjacent restoration projects related to other endeavors. Our hybrid approach harvested coral larvae that had been wasted in both cities. Thus, hybrid solutions are globally required for such cases, and proper early interventions are needed to maintain the genotype power to boost coral adaptability throw global ecological settings.

Potential solutions to environmental conflict on exploitation of fish stocks in palk strait among fishermen of India and Sri Lanka

Illegal catching of fish stocks beyond the borders of India and Sri Lanka by violating the International Maritime Boundary Line (IMBL) by the fishing communities of both countries has become a major international direct environmental conflict between both nations. Overexploitation of natural resources is a keystone environmental problem. It has been reported that Indian fishermen are stealing fish catch worth many millions of US dollars annually from Sri Lankan coastal waters. The bilateral agreements of 1974 and 1976 are frequently violated. The heavy use of trawlers that are not permitted to fish on coastal seas and the use of internationally banned bottom sea nets by Indian poachers are major threats to the coastal resources of north Sri Lanka. Trawlers catch fish flocks unselectively; the catch may include several non-targeted species and juvenile stages of fish, which is leading to species extinction. Arresting and imprisoning of fishermen by coastal guards of both countries (and collecting penalties) continue, and this is an unsustainable way of handling the issue. Sri Lanka has banned bottom trawling since the 6th of July 2017, which is a sustainable solution and beseeched possible greener solutions such as creating awareness, sensitizing fishermen, and promoting the use of GPS navigation, and also provoked conventional solutions such as monitoring or patrolling, which often lead to imprisonment and penalties for trespassing and seizing of fishing trawlers. Restorative solutions such as coral restoration, mangrove restoration, implantation of artificial reefs, and establishing mutually beneficial ‘no catch zone’ along the IMBL and marine reserves (or marine protected areas) by both nations may facilitate preventing the deterioration of fish stocks and ensuring their revival in the region. Above all, if this illegal catching continues, the availability of fish stocks in the Palk Strait region in the next ten years will be in question.

Advancing coral microbiome manipulation to build long-term climate resilience

Coral reefs house one-third of all marine species and are of high cultural and socioeconomic importance. However, coral reefs are under dire threat from climate change and other anthropogenic stressors. Climate change is causing coral bleaching, the breakdown of the symbiosis between the coral host and its algal symbionts, often resulting in coral mortality and the deterioration of these valuable ecosystems. While it is essential to counteract the root causes of climate change, it remains urgent to develop coral restoration and conservation methods that will buy time for coral reefs. The manipulation of the bacterial microbiome that is associated with corals has been suggested as one intervention to improve coral climate resilience. Early coral microbiome-manipulation studies, which are aimed at enhancing bleaching tolerance, have shown promising results, but the inoculated bacteria did generally not persist within the coral microbiome. Here, we highlight the importance of long-term incorporation of bacterial inocula into the microbiome of target corals, as repeated inoculations will be too costly and not feasible on large reef systems like the Great Barrier Reef. Therefore, coral microbiome-manipulation studies need to prioritise approaches that can provide sustained coral climate resilience.

A phenomic modeling approach for using chlorophyll-a fluorescence-based measurements on coral photosymbionts

We test a newly developed instrument prototype which utilizes time-resolved chlorophyll-a fluorescence techniques and fluctuating light to characterize Symbiodiniaceae functional traits across seven different coral species under cultivation as part of ongoing restoration efforts in the Florida Keys. While traditional chlorophyll-a fluorescence techniques only provide a handful of algal biometrics, the system and protocol we have developed generates > 1000 dynamic measurements in a short (~11 min) time frame. Resulting ‘high-content’ algal biometric data revealed distinct phenotypes, which broadly corresponded to genus-level Symbiodiniaceae designations determined using quantitative PCR. Next, algal biometric data from Acropora cervicornis (10 genotypes) and A. palmata (5 genotypes) coral fragments was correlated with bleaching response metrics collected after a two month-long exposure to high temperature. A network analysis identified 1973 correlations (Spearman R > 0.5) between algal biometrics and various bleaching response metrics. These identified biomarkers of thermal stress were then utilized to train a predictive model, and when tested against the same A. cervicornis and A. palmata coral fragments, yielded high correlation (R = 0.92) with measured thermal response (reductions in absorbance by chlorophyll-a). When applied to all seven coral species, the model ranked fragments dominated by Cladocopium or Breviolum symbionts as more bleaching susceptible than corals harboring thermally tolerant symbionts (Durusdinium). While direct testing of bleaching predictions on novel genotypes is still needed, our device and modeling pipeline may help broaden the scalability of existing approaches for determining thermal tolerance in reef corals. Our instrument prototype and analytical pipeline aligns with recent coral restoration assessments that call for the development of novel tools for improving scalability of coral restoration programs.

Identifying correlates of coral‐reef fish biomass on Florida’s Coral Reef to assess potential management actions

Abstract Coral reef fish assemblages are threatened globally, underscoring the need for data‐driven management to reduce threats and restore populations. Comparing fishery management approaches is aided by a detailed understanding of the key factors controlling species’ abundances. The aims of this study were to assess the importance of biophysical factors compared with fishing impacts on the biomass of reef fishes on Florida’s Coral Reef and to evaluate the potential effects of common management interventions on fish biomass. Fishing impact was estimated using a fishery‐independent modelling approach and the biomass of the snapper–grouper complex as a proxy for the effects of fishing. Using a separate subset of data from underwater fish surveys, estimated fishing impact was then combined with 18 biophysical variables to model the current biomass of all reef fish species, the snapper–grouper complex, grazing species and species collected for aquaria. Models explained between 51 and 64% of the variance in fish biomass for the fish groups. The strongest predictor of biomass in the snapper–grouper complex was fishing impact (accounting for 25.2% of the explained variance), whereas reef complexity was the strongest predictor for all other groups. High‐resolution maps were produced from the statistical models, including maps of current fish biomass and maps of potential biomass under several management scenarios: a no‐take marine reserve, moderate and extensive coral restoration and the addition of artificial benthic structure. Adding structure had the largest single impact on predicted fish biomass (23–72% increase from current estimated levels). However, beneficial synergies emerged when combining habitat‐based management and fishing closures, with some combinations resulting in a reef‐wide averaged 89% increase in biomass relative to current estimated levels. The results suggest that conservation strategies aimed at protecting and increasing structural reef complexity should be an important part of fishery management discussions.

Geological Perspectives on the Degradation and Restoration of Coral Reefs

The growth and maintenance of coral-reef structures built over 1000s of years serve as the foundation for the myriad ecosystem services reefs provide to society. Predicting how reef building will change in the future is, therefore, critical to designing effective coral-reef management strategies; however, it is challenging to accurately forecast the long-term process of reef accretion based on short-term ecological studies alone. Geological records, particularly those from sensitive, marginal reef environments such as the subtropical reef system of south Florida, are essential for projecting changes in reef accretion, and for optimizing strategies for coral-reef management. Using a combination of millennial-scale reconstructions of reef accretion and paleoecology from reef cores, and contemporary carbonate budget modeling, I evaluated the past, present, and a possible future of coral-reef development in south Florida. I will show that climate has been the primary control on the rate and extent of regional reef development and, by 3000 years ago, reef accretion was negligible throughout the region. This confined the ecosystem to an unstable equilibrium in which a veneer of living coral was the only barrier to catastrophic reef erosion. In recent decades, climate and other anthropogenic disturbances have pushed many reefs into a novel state characterized by a loss of reef-building corals that is unprecedented in the geological record. These changes have unbalanced Florida’s carbonate budgets, leading to increases in reef-framework erosion. I will show that there is hope for ongoing coral restoration efforts to revive reef growth on a local scale to levels comparable to long-term natural baselines; however, the central role of climate in both the millennial-scale declines in reef building and the modern decline in coral populations suggests that the efficacy of these local efforts will be limited without global-scale action to mitigate anthropogenic climate change.

Symbiont composition and coral genotype determines massive coral species performance under end-of-century climate scenarios

The recent decline of coral health and substantial loss of coral cover along Florida’s Coral Reef (FCR) results from local stressors such as degraded water quality and disease outbreaks in addition to anthropogenically driven global stressors including ocean warming and acidification. Intervention strategies intended for the restoration of degraded reef habitats need a better understanding of the influence of ocean warming and acidification on coral health to target coral species and individual genotypes that may be more resistant or resilient to such stressors. Here, we examined a suite of physiological traits (coral host and algal symbiont) in response to experimentally elevated water temperatures and pCO2 levels, both separately and in concert, using threatened reef-building corals Pseudodiploria clivosa and Orbicella faveolata reared within a land-based coral nursery. After two months of exposure, responses differed by coral species, where P. clivosa showed declined physiology in response to combined ocean warming and acidification stress and ocean warming alone, whereas O. faveolata showed a positive response under ocean acidification. Responses to temperature could be associated with the algal symbionts harbored, as P. clivosa was dominated by the thermally sensitive Breviolum, and O. faveolata was dominated by the thermally tolerant Durusdinium. Additionally, corals were raised in well-sourced seawater that was naturally high in pCO2, which could have led to corals acclimating to acidified conditions. Of the three P. clivosa genets tested, we determined a top-performing genotype under the combined warming and acidification treatment. O. faveolata, however, displayed high genet variation by treatment and phenotypic trait, making genotype performance rankings challenging to discern. The evidence provided in this study demonstrates that high phenotypic variation in nursery-reared corals contributes to variable warming-acidification responses, suggesting that high-standing genetic variation in nursery-reared corals could support diverse coral restoration population outcomes along FCR.

Novel infrastructure for coral gardening and reefscaping

Since 1950, coral abundance has declined worldwide by an estimated 60%, and further dramatic declines are predicted. Although global reductions in carbon emissions are essential to prevent further loss, coral reef restoration has become imperative to maintain the ecosystem services that coral reefs provide to humans at local scales. Yet, currently coral restoration and gardening efforts are too expensive to scale up due to the labor-intensive nature of the methods and low success rates. Here, we present a suite of technologies that improve coral reef restoration and rehabilitation’s scalability, efficiency, and effectiveness. Our modular technologies are designed to streamline in and ex situ nursery workflows, reduce maintenance times, solve problems in transporting corals to outplanting sites, and enable rapid outplanting on natural and artificial substrates. These novel structures can act as coral seeding hubs, which placed strategically, can have the capacity to enhance coral reproduction and replenish degraded nearby reefs with larvae. They can be applied to coral restoration and reefscaping, complemented by unique eco-friendly, low-carbon-emission structures for the creation of architecturally and visually appealing habitats and underwater landscapes. Our technologies integrate novel monitoring approaches that support intelligent solutions to track genotypes, optimize and control stock management, apply assisted evolution approaches, and adaptive management through long-term monitoring.

Coral restoration patents are disconnected from academic research and restoration practitioners

Global warming and other anthropogenic impacts have driven coral reef degradation on a global scale to unprecedented levels of decline, with further dramatic deterioration predicted by the end of this century. Along with a drastic reduction in carbon emissions, we face an imperative to restore and maintain marine habitats to secure the ecosystem services they provide. While terrestrial systems have benefited from the agricultural revolution that provided industrial tools for effective habitat restoration, limited access to marine environments has inhibited similar levels of innovation resulting in a lack of cost-effective and scalable solutions. Commercial off-the-shelf technologies to cater to this growing industry are still absent. Here we conducted a systematic analysis of patent and scientific literature data as indicators of research and development (R&D) output in the field of coral restoration. We identify technology growth trends, key areas of technological development, and their geographical distribution. While the number of inventions filed for coral restoration is on the rise, similar to the published academic literature, the stakeholders leading both fields are unrelated. Academic research appears to lack translation into inventions for commercialization. Intellectual property protection further seems to be spearheaded by a few countries and is often limited in its application to national jurisdictions, with China dominating this sector. This does not mirror the distribution of current and need for coral restoration efforts globally. Here we discuss potential differences in cultural, socio-economic, and philosophical ideologies that drive these divergences and their impact as inhibitors or promoters of innovations targeting coral restoration solutions.

Enhancing reef restoration by assessing stakeholder knowledge, attitudes, and preferences

Coral restoration has largely focused on improving techniques and biological yield to hasten reef recovery. However, as socioeconomic considerations can affect restoration success, it is important to also consider inputs from various stakeholders in the design and execution of restoration projects. Through online questionnaires, the knowledge levels and attitudes of 142 participants toward coral ecology and restoration in Singapore, and their preferences toward species traits they felt were most beneficial for restoring reefs, were analyzed. Comprising varied sociodemographic profiles and stakeholder groups, participants fared better in general coral biology (up to 90% of answers correct) than local coastal resource management (35% of answers correct). More than 79% of participants agreed that Singapore's reefs were rapidly degrading and required restoration to slow the decline; however, over 63% of them disagreed that restoration was the sole domain of scientists or that the topic had been sufficiently communicated to the public. These knowledge scores and attitudes were most influenced by stakeholder group, educational level, and familiarity with local reefs, underscoring the need to improve environmental education and science communication to these groups. In the trait prioritization exercise involving 76 respondents, resilience and resistance to stress were regarded as most important for restoring reefs. Marine science professionals and nondivers preferred using species that could cope with stress, while nature enthusiasts and recreational divers considered habitat contribution by various coral growth forms as more important. The adaptable framework here facilitates integration of stakeholder inputs with the necessary strategies to boost restoration outcomes.

Effectiveness of different nursery designs for the restoration of the threatened coral Acropora cervicornis in Culebra, Puerto Rico

The threatened staghorn coral Acropora cervicornis is an important reef-builder species in the Caribbean. Its ecological importance and critical status have prompted efforts to restore degraded populations. In this respect, nursery-based programmes have effectively propagated A. cervicornis and helped to increase population sizes. Despite many advances in low-cost coral nursery designs, there is still a need to increase productivity while reducing costs. This study evaluates A. cervicornis demographic performance in two propagation structures: floating trees (FT) and floating horizontal frames (HF). Two equal-sized fragments were collected from 50 healthy staghorn coral colonies. Each fragment was placed into an FT or HF design. Survival, growth, branching, and productivity were recorded for seven months. To address the cost-effectiveness of the coral propagation techniques, we compared the total cost of producing corals between the two designs. Survival was similar, with 91% and 92% of the coral fragments surviving in the FT and HF, respectively. Although colonies in HF nurseries grew faster and produced more branches than those in FT nurseries, these differences were not statistically significant. Likewise, productivity did not differ statistically between nursery designs despite fragments in HF nurseries being 1.5 times more productive than those in FT nurseries. Because of the similarity in demographic performance, the selection of nursery designs could be based solely on their cost-effectiveness. In this respect, the cost-effectiveness analysis shows that producing corals using HF costs about 70% less than FT. Thus, we conclude that floating horizontal frame (HF) nurseries are better for propagating A. cervicornis and accelerating coral restoration activities.

Preliminary result of population structure of reef fishes in coral reef restoration sites in Tun Sakaran Marine Park, Semporna, Sabah

Restoration of coral reefs at the Tun Sakaran Marine Park (TSMP) started in 2009. Various methods are adopted, although the Coral Frame method is preferred mainly due to the low maintenance cost and its durability, and is currently still being used. However, since the beginning of its deployment, there has been little study on the effectiveness of the coral restoration project. Thus, this study was conducted to determine the population structure of indicator coral reef fish around the coral frames. Two study sites (Site 1: Bohey Dulang; Site 2: Mantabuan) with existing coral frames within the TSMP were selected. At each site, a baited remote underwater video system ( BRUVS), was deployed, and each was set to capture approximately one-hour footage. The first BRUVS deployment of this 24-month project was made on 21 July 2020, during the peak of the Southwest Monsoon. A total of 20 families (32 species) and 19 families (42 species) were recorded at Site 1 and Site 2, respectively. The Small-tooth whiptail, Pentapodus caninus (MaxN:14) and fusilier, Caesio sp. (MaxN: 101) are the most abundant species at Site 1 and Site 2, respectively. The preliminary findings reveal a low abundance and diversity counts of indicator reef fish (Serranidae, Labridae, Scaridae and Lutjanidae) at the coral restoration sites within TSMP. However, it is suspected that opportunistic local fishermen try their luck to fish in restricted parts of the park (pers. Observ.), while local fishermen try to play the game of 'mouse and cat' with the Park's Law Enforcement.

Insights into coral restoration projects in Japan

Coral transplantation, including out-plantation, is performed worldwide to restore coral reefs. To date, >300 000 coral colonies have been transplanted in Japan, and the survival rate of transplanted corals is mostly <20% after 4 years. Here, I highlight problems that have arisen as a result of coral restoration projects in Japan and discuss solutions that may maximise transplantation effectiveness. The government, companies, and researchers have focused on the positive aspects of transplantation technology and new biological findings; however, negative aspects such as the high mortality rate for transplanted corals and high maintenance costs have garnered less attention. Uncritical and incomplete coverage of reef projects by the mass media has led to a misconception that the coral reef crisis can be resolved by current biological engineering solutions. Therefore, transplantation has been used to justify sea reclamation including marine leisure facilities and various other construction projects. Consequently, approximately 400 ha of coral reefs in Japan have been lost in only a decade. Understanding the limitations of transplantation techniques is necessary, and hence, I propose that coral transplantation guidelines be adopted to prevent further loss. Further advances in transplantation technology are required to increase scalability and cost-effectiveness and improve survival/performance; however, practitioners, researchers, companies, and governments, especially in environmentally unconscious countries, should clearly state that coral transplantation cannot restore large-scale coral reef ecosystems and should not be used to justify land reclamation affecting reefs, as mentioned in most international guidelines. Moreover, when coral transplantation and seedling production are used for environmental education, the death of transplanted corals and difficulties underlying artificial coral regeneration should be clearly explained. Effective coral transplantation use within a conservation framework is critical to avoid high and unfounded expectations.

Health monitoring status of corals in Gulf of Mannar and Palk Bay (India) with special reference to coral bleaching event

Abstract. Sadhukhan K, Chatragadda E, Shunmugaraj T, Murthy MVR. 2022. Health monitoring status of corals in Gulf of Mannar and Palk Bay (India) with special reference to coral bleaching event. Indo Pac J Ocean Life 6: 72-84. Coral reef ecosystems are highly important regarding ecological, cultural, and economic values. Unfortunately, these ecosystems are declining rapidly due to climate change and local anthropogenic threats. The present study assessed the coral reef health status in the Gulf of Mannar (GoM) and Palk Bay (PB), India, to understand the diversity and abundance of corals and the bleaching vulnerability of the reef areas. Extensive underwater surveys were conducted from August 2018 to August 2020. Line intercept transect methods were employed in triplicates and estimated the bleaching-mediated reef threats. As a result, the average live coral cover of the Gulf of Mannar was 39.55±15.45% (Mean±SD), and Palk Bay was 28.40±14.60%, of which Mandapam Group of Islands has maximum live coral coverage (51.80±15.10%). Severe coral bleaching was also observed in the Gulf of Mannar and Palk Bay during the summer of two the consecutive year, 2019 and 2020, triggered by increased sea surface temperature (SST) of 4°C-5°C than the average temperature (28°C-31°C). The current study highlights the detailed distribution of the coral community with comparative analysis since 2000 and the adaptive response of native coral species to bleaching events that will help to implement management interventions like coral restoration of those native species to strengthen the reef resilience in the Gulf of Mannar and Palk Bay.

Thermal priming and bleaching hormesis in the staghorn coral, Acropora cervicornis (Lamarck 1816)

Stress memory is a highly conserved phenomenon that enables the survival of organisms. There is evidence of stress memory in stony corals, but its costs and benefits remain largely unknown. To characterize coral stress memory, eight genets of Acropora cervicornis corals were primed with varying doses of thermal stress in the laboratory, allowed to recover for eight days and then experimentally bleached. Symbiont density and chlorophyll decreased linearly with increasing priming intensity, demonstrating a dose-dependent upfront ‘cost’ of priming. The highest priming dose (8.8 °C·days) led to bleaching after priming and mortality at the end of the recovery period, however, in lower priming intensity treatments, differences in symbiont density and chlorophyll detected immediately after priming did not persist after recovery. Primed corals did not bleach significantly less than naïve corals, owing to high within treatment variance between genets. However, the relationship between priming intensity (°C·days) and thermal bleaching severity (i.e., symbiont density) was hormetic (p = 0.055). Priming with low doses of thermal stress (1.8 to 4.6 °C·days) resulted in 32–51% greater symbiont retention, but the highest dose (8.8 °C·days) led to severe bleaching like that observed in naïve corals. This study empirically demonstrates coral bleaching hormesis in the laboratory, providing support for environmentally mediated priming in Scleractinians. The presence of coral bleaching hormesis suggests there may be the potential to extend resilient bleaching phenotypes for some corals. However, not all host genotypes may benefit from hardening, an essential consideration in the applicability of stress hardening for coral restoration.

Coral restoration and adaptation in Australia: The first five years.

While coral reefs in Australia have historically been a showcase of conventional management informed by research, recent declines in coral cover have triggered efforts to innovate and integrate intervention and restoration actions into management frameworks. Here we outline the multi-faceted intervention approaches that have developed in Australia since 2017, from newly implemented in-water programs, research to enhance coral resilience and investigations into socio-economic perspectives on restoration goals. We describe in-water projects using coral gardening, substrate stabilisation, coral repositioning, macro-algae removal, and larval-based restoration techniques. Three areas of research focus are also presented to illustrate the breadth of Australian research on coral restoration, (1) the transdisciplinary Reef Restoration and Adaptation Program (RRAP), one of the world's largest research and development programs focused on coral reefs, (2) interventions to enhance coral performance under climate change, and (3) research into socio-cultural perspectives. Together, these projects and the recent research focus reflect an increasing urgency for action to confront the coral reef crisis, develop new and additional tools to manage coral reefs, and the consequent increase in funding opportunities and management appetite for implementation. The rapid progress in trialling and deploying coral restoration in Australia builds on decades of overseas experience, and advances in research and development are showing positive signs that coral restoration can be a valuable tool to improve resilience at local scales (i.e., high early survival rates across a variety of methods and coral species, strong community engagement with local stakeholders). RRAP is focused on creating interventions to help coral reefs at multiple scales, from micro scales (i.e., interventions targeting small areas within a specific reef site) to large scales (i.e., interventions targeting core ecosystem function and social-economic values at multiple select sites across the Great Barrier Reef) to resist, adapt to and recover from the impacts of climate change. None of these interventions aim to single-handedly restore the entirety of the Great Barrier Reef, nor do they negate the importance of urgent climate change mitigation action.

Evidence for adaptive morphological plasticity in the Caribbean coral, Acropora cervicornis

Genotype-by-environment interactions (GxE) indicate that variation in organismal traits cannot be explained by fixed effects of genetics or site-specific plastic responses alone. For tropical coral reefs experiencing dramatic environmental change, identifying the contributions of genotype, environment, and GxE on coral performance will be vital for both predicting persistence and developing restoration strategies. We quantified the impacts of G, E, and GxE on the morphology and survival of the endangered coral, Acropora cervicornis, through an in situ transplant experiment exposing common garden (nursery)-raised clones of ten genotypes to nine reef sites in the Florida Keys. By fate-tracking outplants over one year with colony-level 3D photogrammetry, we uncovered significant GxE on coral size, shape, and survivorship, indicating that no universal winner exists in terms of colony performance. Rather than differences in mean trait values, we found that individual-level morphological plasticity is adaptive in that the most plastic individuals also exhibited the fastest growth and highest survival. This indicates that adaptive morphological plasticity may continue to evolve, influencing the success of A. cervicornis and resulting reef communities in a changing climate. As focal reefs are active restoration sites, the knowledge that variation in phenotype is an important predictor of performance can be directly applied to restoration planning. Taken together, these results establish A. cervicornis as a system for studying the ecoevolutionary dynamics of phenotypic plasticity that also can inform genetic- and environment-based strategies for coral restoration.