Yimnang Golbuu

In a rapidly warming climate, species persistence will increasingly depend on thermal evolution. Yet how evolution-informed conservation should harness spatial gradients of heatwave-driven selection remains unclear. Here, we extend an eco-evolutionary metapopulation model of reef-building corals to incorporate marine heatwaves, manageable recurrent non-climatic disturbances, and two conservation interventions: local protection and restoration. Prioritising efforts toward heatwave-exposed "hotspot" populations consistently generated the greatest evolutionary gains in heat tolerance, but strategies for improving coral abundance (coverage) were context dependent. Under a 2°C Paris Agreement scenario, protecting thermal refugia and restoring hotspots were optimal strategies for improving coverage. However, under a more plausible 3°C scenario, restoring refugia maximised near-term coverage gains whereas targeting hotspots delivered greatest long-term benefits. This fundamental time-dependent trade-off in conservation outcomes suggests potential for portfolio approaches or adaptive management that alters spatial prioritisations strategically over time. However, further simulations show neither such approach could recover both near- and long-term coral coverage benefits, likely because evolutionary adaptation is gradual and cumulative, becoming increasingly important as warming intensifies. Investing heavily in heatwave-exposed locations among the most vulnerable to degradation could be politically challenging, but rapidly implementing such evolution-informed spatial conservation is critical, as delays can curtail long-term evolutionary and ecological outcomes.

Sexual coral propagation is an emerging technique capable of producing large numbers of corals for coral transplantation and reef rehabilitation. In contrast to asexual coral propagation, sexual propagation increases genotypic diversity and can be used for selective breeding to enhance coral heat tolerance or other desirable traits. However, implementation at meaningful ecological scales is hindered by high mortality during early life stages, high costs associated with nursery rearing facilities, and labour-intensive outplanting methods. To overcome these issues, we developed the CoralAssist Plug (CAP), a ceramic device designed for the rapid and cost-effective outplanting of sexually propagated corals in large numbers that maximises post-outplant survivorship. CAPs combine three important functional features: 1) built-in microrefugia to protect juvenile corals from grazing, 2) a relatively small size, 3 by 1 cm, that is easy to handle and stack efficiently without compromising the survivorship of corals, and 3) a hole in the middle that facilitates handling and attachment. CAPs were settled with Acropora aff. digitifera and outplanted to a reef crest after 1 to 6 months of ex situ nursery rearing. A 3-person dive team was able to outplant ~120 CAPs in one 90-minute shallow dive (just over 2 minutes per CAP per person). With longer nursery durations of 6 months, it was possible to achieve 36 % yield (i.e., the proportion of devices with a surviving coral) 4-years post-outplant. With nursery durations shortened to 1 month, we were able to attain 24 % yield 3-years post-outplant. Microrefugia significantly enhanced post-outplant survivorship leading to an 11 % increase in yield 4 years post outplant compared to devices without microrefugia. Outplanted corals that had reached adult size, were self-attached and were reproductively mature after 4 years. Our results suggest that CAPs can play a meaningful role in reef rehabilitation by efficiently introducing sexually propagated corals into natural populations with clear applications to assisted evolution techniques, such as selective breeding.

Monitoring habitat-forming species, such as scleractinian corals, is crucial for managing ecosystems and biodiversity. Yet for assessing population health, challenges remain in reconciling conventional areal coverage surveys with individual-based demographic techniques. Here, we explore both monitoring approaches to characterize the population dynamics of the reef-building coral, Acropora cf. digitifera , on a West Pacific outer reef using photogrammetry reef mapping data spanning 5 years. Tracking 906 coral colonies showed that those exceeding approximately 10 cm diameter exhibit the fastest planar growth but also suffer excess mortality, possibly owing to increased structural vulnerability to dislodgement by wave energy or to other factors, such as disease or predation, that may be exacerbated by senescence. Area-controlled orthomosaic subsampling paired to integral projection modelling revealed a consistent decline in population density, as recruitment was insufficient to balance losses of larger colonies. Yet, total areal coverage and median colony size increased over the study, suggesting this disequilibrium population is on a recovery trajectory from past disturbance and heavily reliant on sporadic recruitment pulses not detected in our study. We find that conventional areal monitoring and demographic approaches can yield contrasting conclusions about population dynamics. Reconciling these differences for disequilibrium populations requires long-term demographic data over periods long enough to detect infrequent yet critical demographic events such as large post-disturbance recruitment events.

Disseminating research through academic publishing is essential for contributing to global knowledge, advancing critical fields and finding solutions to humanity’s challenges. However, for Pacific Islanders, navigating the path to publication can feel like crossing a vast ocean while weighed down by systemic barriers that make sharing knowledge, lived experiences and unique worldviews with the broader academic community difficult. Using an Indigenous talk story methodology (talanoa), discussions were held with early- and mid-career Pacific Island researchers to identify the main barriers collectively faced. These barriers included insufficient time and funding, poor recognition of Indigenous research methodologies, inequitable partnerships with researchers from the Global North, lack of local academic mentors, linguistic hurdles and biases in the academic system. We outline strategies aimed at dismantling systemic barriers faced by Pacific researchers when designing and conducting research, writing manuscripts and publishing in the academic literature. Our discussion highlights pathways for greater inclusion of Pacific scholars in academic publishing to which Global North researchers, academic journals and funding agencies can contribute. Removing barriers is essential to leverage the unique insights of Pacific Island researchers, whose contributions are vital for developing locally-driven, globally impactful solutions to the biodiversity and climate change crises.

High mortality of juvenile corals hinder both the natural recovery of populations and the successful implementation of restoration efforts. Grazing is a significant cause of juvenile coral mortality, and grazer exclusion devices have been shown to increase juvenile coral survivorship. However, most experiments have used cages that typically alter water flow and light conditions, making it difficult to separate abiotic effects from those of grazing. Here, we test whether grazing deterrents can increase the survival and growth of six-month-old Acropora digitifera juveniles outplanted to a shallow reef crest, using arrangements of two or four long or short masonry nails designed to physically exclude larger grazers (e.g., parrotfish) while minimising abiotic changes. By the end of our study, colonies with deterrents had significantly larger planar area (almost tenfold for the most effective treatment), more branches, greater height, and higher survival than those without deterrents. A critical period in this study was the first week after outplanting when colonies with deterrents had significantly less tissue area loss from grazing than those without. Lower area loss in the first week was associated with significantly higher survival over the following 14 months, with an almost threefold improvement for the most effective treatment. For heavily grazed systems, our study highlights the importance of incorporating grazing deterrents into outplant devices to counteract the negative impact of large grazers on newly outplanted juvenile corals and boost restoration success.

Marine heatwaves are intensifying under climate change, exposing populations of reef-building corals to mass mortality and intense selective pressure. It remains unknown whether adaptation can keep pace with warming and maintain reef functioning. We have developed an eco-evolutionary metapopulation model for Acropora , an ecologically important yet thermally sensitive coral taxon. We found that, although corals have some adaptation capacity, they will suffer severe heatwave-induced declines over the coming decades. For a future in which emissions lead to ~3°C of global warming, natural selection could allow populations to persist, albeit in severely depleted states with elevated extinction risk and potential loss of ecosystem functioning. Yet, for thermally sensitive coral populations to thrive beyond 2050, there must be rapid reductions of greenhouse gas emissions that limit global warming to 2°C.

Marine heatwaves are becoming more frequent, widespread and severe, causing mass coral bleaching and mortality. Natural adaptation may be insufficient to keep pace with climate warming, leading to calls for selective breeding interventions to enhance the ability of corals to survive such heatwaves, i.e., their heat tolerance. However, the heritability of this trait–a prerequisite for such approaches–remains unknown. We show that selecting parent colonies for high rather than low heat tolerance increased the tolerance of adult offspring (3–4-year-olds). This result held for the response to both 1-week +3.5 °C and 1-month +2.5 °C simulated marine heatwaves. In each case, narrow-sense heritability (h²) estimates are between 0.2 and 0.3, demonstrating a substantial genetic basis of heat tolerance. The phenotypic variability identified in this population could theoretically be leveraged to enhance heat tolerance by up to 1 °C-week within one generation. Concerningly, selective breeding for short-stress tolerance did not improve the ability of offspring to survive the long heat stress exposure. With no genetic correlation detected, these traits may be subject to independent genetic controls. Our finding on the heritability of coral heat tolerance indicates that selective breeding could be a viable tool to improve population resilience. Yet, the moderate levels of enhancement we found suggest that the effectiveness of such interventions also demands urgent climate action.

High mortality rates of juvenile corals hinder both the natural recovery of populations and the successful implementation of restoration efforts. Grazing is a significant cause of juvenile coral mortality, and grazer exclusion devices have been shown to increase juvenile coral survivorship. However, most experiments have used cages that typically alter water flow and light conditions and exclude grazers of most sizes, making it difficult to quantify the effects of large grazers alone. Here, we test whether deterring large grazers can increase the survival and growth of six-month-old Acropora digitifera juveniles outplanted to a shallow reef crest, using arrangements of two or four long or short masonry nails that selectively exclude larger grazers (e.g., parrotfish) while minimising abiotic changes. By the end of our study, colonies with deterrents had significantly larger planar area (almost tenfold for the most effective treatment), more branches, greater height, and enhanced survival than those without deterrents. A critical period is the first week after outplanting when colonies with deterrents had significantly less tissue loss from grazing than those without. Less tissue loss in the first week was associated with significantly higher survival over the following 14 months, with an almost threefold improvement for the most effective treatment. For heavily grazed systems, our study highlights the importance of incorporating grazing deterrents into outplant devices to counteract the negative impact of large grazers on outplanted juvenile coral survival and boost restoration success.

Marine heatwaves and mass bleaching have led to global declines in coral reefs. Corals can adapt, yet, to what extent local variations in thermal stress regimes influence heat tolerance and adaptive potential remains uncertain. Here we identify persistent local-scale thermal refugia and hotspots among the reefs of a remote Pacific archipelago, based on 36 years of satellite-sensed temperatures. Theory suggests that hotspots should promote coral heat tolerance through acclimatisation and directional selection. While historic patterns of mass bleaching and marine heatwaves align with this expectation, we find a contrasting pattern for a single species, Acropora digitifera , exposed to a marine heatwave experiment. Higher heat tolerance at thermal refugia (+0.7 °C-weeks) and correlations with other traits suggest that non-thermal selective pressures may also influence heat tolerance. We also uncover widespread heat tolerance variability, indicating climate adaptation potential. Compared to the least-tolerant 10% of the A. digitifera population, the most-tolerant 10% could withstand an additional heat stress of 5.2 and 4.1 °C-weeks for thermal refugia and hotspots, respectively. Despite expectations, local-scale thermal refugia can harbour higher heat tolerance, and mass bleaching patterns do not necessarily predict species responses. This has important implications for designing climate-smart initiatives to tackle global-scale adaptive management problems.

Bumphead parrotfish (Bolbometopon muricatum) and Napoleon wrasse (Cheilinus undulatus) are large, charismatic species with high economic and cultural value in Palau and are important for ecosystem function. As a result of intense fishing pressure, landings in Palau for both species declined dramatically in the 1990s and, in response, national legislation was enacted in 2006 that imposed a total ban on the extraction, possession, and sale of both species. In 2013 and 2021, fisheries‐independent stock assessments were conducted and found that the spawning potential ratios (SPRs) for bumphead parrotfish increased slightly from 30% to 34%. Conversely, the SPRs for Napoleon wrasse declined from 12% in 2013 to 4% in 2021. Despite the fishery being closed since 2006, these data suggest the likelihood of significant poaching, resulting in low SPR values, particularly for Napoleon wrasse. Prior to the COVID‐19 pandemic, marine tourism played a central role in the economic and social life of Palau. A willingness‐to‐pay survey found that divers would pay $1.27 million (2020 USD) more for strictly managed catches of both species, and nearly $3.00 million more if the fishery remained closed. The total market value for bumphead parrotfish peaked in 1995 at $112,190. The peak total market value for Napoleon wrasse was $66,434 in 2002. The welfare gain/loss for diver tourism is an order of magnitude greater than the fishery market gain/loss, and healthy marine ecosystems are essential for the post‐COVID‐19 economic recovery of Palau. However, because of the cultural importance of these species, there is a desire to manage this fishery for customary use. Opening a general subsistence harvest season is not recommended ecologically; however, the results suggest that if the SPR of bumphead parrotfish can recover to 40%, a limited quota of individuals with a total length of >95 cm could be sustained, which could be allocated via lottery. However, the fishery for Napoleon wrasse should remain closed given the extremely low SPR values and limited number of large adults in the population.