Shading coral from high solar irradiance has been suggested as an effective approach to reduce the risk of coral mortality due to bleaching. Spraying seawater droplets is potentially an effective way to provide shading at the scale of a single reef or a collection of reefs. For the first time, we provide in situ characterizations of artificially made seawater droplet plumes over coral reefs. Here, we analyzed 21 crosswind transects at the surface level carried out at multiple downwind distances of 1.5 km or less from the prototype seawater droplet generator. The average particle number size distribution of the sprayed seawater droplets showed a primary mode of 124 nm dry diameter and agreed with that collected in laboratory experiments. The observed particle number concentration of seawater droplet aerosols ranged from 103 to 105 cm-3 and exhibited a monotonic decreasing trend with increasing plume transport time downwind of the seawater droplet generator. With a downwind transport time scale of up to 200 s, the estimated plume width can expand from 50 m to nearly 500 m. The results of this study will assist in estimating the shading provided by the seawater droplet plume and inform future scale-up of the technique on target reef areas.

The dramatic decline of reef-building corals calls for a better understanding of coral adaptation to ocean warming. Here, we characterize genetic diversity of the widespread genus Acropora by building a genomic database of 595 coral samples from different oceanic regions-from the Great Barrier Reef to the Persian Gulf. Through genome-environment associations, we find that different Acropora species show parallel evolutionary signals of heat-adaptation in the same genomic regions, pointing to genes associated with molecular heat shock responses and symbiosis. We then project the present and the predicted future distribution of heat-adapted genotypes across reefs worldwide. Reefs projected with low frequency of heat-adapted genotypes display higher rates of Acropora decline, indicating a potential genomic vulnerability to heat exposure. Our projections also suggest a transition where heat-adapted genotypes will spread at least until 2040. However, this transition will likely involve mass mortality of entire non-adapted populations and a consequent erosion of Acropora genetic diversity. This genetic diversity loss could hinder the capacity of Acropora to adapt to the more extreme heatwaves projected beyond 2040. Genomic vulnerability and genetic diversity loss estimates can be used to reassess which coral reefs are at risk and their conservation.

The coral microbiome is a critical component of coral health and resilience, yet it is unclear what factors drive coral microbiome composition, especially within the context of coral bleaching. Here, we use whole genome sequencing data combined with a machine learning approach (RDAforest) to assess predictors of the microbiome in 208 colonies of Acropora millepora from 12 reef sites in the Central Great Barrier Reef during a 2016 bleaching event. We characterized microbiome variation using k-mers. While some environmental variables, such as chlorophyll seasonal range and maximum degree heating weeks, were associated with microbiome composition, we find that host genetics and dominant photosymbionts were more powerful predictors. In contrast, bleaching score had negligible predictive power. The coral's microbiome therefore correlates with dominant photosymbiont identity even during a bleaching event. The association of the microbiome with the environment suggests that the coral microbiome can serve as a proxy for environmental variation when environment cannot be measured directly, which may be especially useful in ancient DNA studies.

Effect of marine reserve status on coral seeding in the inshore Great Barrier Reef

Unsealed roads and their construction and maintenance are a direct anthropogenic source of sediment in river catchments. Maintenance practices use graders to form the road crown, add gravel material, reshape table and diversion drains, and remove vegetation from batters. Repeat high-resolution terrestrial laser scanning (TLS) was used to quantify unsealed road erosion at six road segments (2.5 ha) over two years each with average rainfall to assess (1) baseline erosion from status quo maintenance, and (2) changes in erosion by applying Best Management Practices (BMPs) to reduce fine sediment delivered to the Great Barrier Reef (GBR). Baseline erosion rates were 132 t/ha/yr locally of all size classes and 38 t/ha/yr < 20 µm to GBR, higher than natural catchment rates (<2 t/ha/yr). Suspended sediment concentrations (<20 µm) were 10 times higher downstream of the road crossings compared to upstream. BMPs implemented in the second year included no grading disturbance of drains and batters for grass recovery, woody vegetation control with herbicide, drain rock lining or grade control structures, rock mulching steep batters, rock chutes at gully heads, and rock mattress floodways. Normalised by a control segment, vegetation recovery on batters and drains resulted in the lowest reduction in erosion (22%), compared to the addition of rock mulch and check dams (42-43%) and more frequent water diversion (69%). Wholistic management funding for road condition and safety; vegetation and weed spread; sheet, rill and gully erosion; and GBR pollution should be treated as a complete package by Federal, State, and Local governments.

Abstract During the recent fourth global mass coral bleaching event, the Great Barrier Reef (GBR) experienced the highest temperatures for centuries and widespread bleaching. For massive, long-lived Goniopora, bleaching coincided with a black band disease (BBD) epizootic at One Tree Reef (OTR). This necrotic wasting disease, typically rare on the GBR, appeared along the edge of bleached polyps. We tracked 112 Goniopora colonies from bleaching onset through winter to summer in seven surveys. In February 2024, 75% of colonies were bleached, and 4% of these had BBD. By April, 61% of bleached colonies had an aggressive black band invading the tissue. For heat stressed and diseased Goniopora, winter cooling did not promote substantial recovery with 75% of tagged colonies dead by October. Only 24% of tagged colonies recovered, albeit with partial mortality. Population surveys at two sites showed a similar bleaching-disease pattern with high mortality by October (46% and 66%). Repeated health assessments revealed a link between bleaching, disease and heat in the demise of these normally resilient massive colonies, many of which have been lost at OTR. Understanding the connection between the ‘evil twins’ of bleaching and disease is important as corals are faced with unprecedented thermal anomalies.

Decodon erythroleukos sp. nov. is described based on three specimens: the holotype from Okinawa, southern Japan, and one paratype each from Jewell Reef, Great Barrier Reef in Australia, and New Caledonia. The new species appears most closely related to the sympatric Decodon pacificus, sharing similar meristic and morphometric details and differing primarily based on colouration. However, molecular analysis of the mitochondrial COI gene reveals a substantial pair-wise difference of 6.2%-6.9% between the two species. Decodon pacificus is rediagnosed based on the holotype and newly collected material, and its hitherto unknown juveniles are detailed and their live colouration illustrated for the first time. Phylogenetic relationships among species of Decodon are investigated based on mitochondrial and nuclear sequence data, and a revised key to species is provided.

ABSTRACT Environmental communication has failed the Great Barrier Reef. After fifty years of communicating the need for protection and conservation, the Reef—like coral reefs globally—remains on the brink of ecological collapse. Australians and international communities are deeply connected to the Reef, a connection reflected in its central place in environmental policy and political debate, its economic significance to tourism, mining, fishing and related industries, and the vast human and financial resources invested in its management. In recent years it has also become a stark symbol of climate impacts in a world still committed to fossil fuel use and development. This paper traces the long-standing recognition of industrial threats to the Reef, emerging alongside global environmental consciousness in the late 1960s, through fifty years of protective measures, to its current position as a litmus test for climate change. It turns the academic lens inward to consider how environmental communication—in theory and practice—has failed something so spectacular, so spectacularly. The Great Barrier Reef serves as a case study for examining the limitations of modern environmental communication and underscores the urgent need for critical self-reflexivity in a discipline operating at the frontlines of communicating escalating ecological crises.

The Great Barrier Reef (GBR) is one of the world’s most iconic tourism destinations, supporting local economies along Australia’s northeast coast. The COVID-19 pandemic severely disrupted global tourism, with particularly acute effects on regions like the GBR that depend heavily on inbound visitors. Using a multi-scalar resilience framework grounded in ecological theory and regional studies scholarship, we analyse economic indicators of impact and recovery across spatial and functional scales in the GBR region. Drawing on monthly and annual data from 2013 to 2023, we examine how tourism and employment patterns in the GBR marine park and surrounding coastal areas responded to pandemic-related shocks and recovery phases. Our findings reveal marked variation in resilience across time, space, and scale. Marine-based tourism recovered more slowly than broader regional visitation, while remote and tourism-dependent subregions were more vulnerable to disruption. In contrast, employment impacts were less pronounced, likely cushioned by national policy interventions such as the JobKeeper wage subsidy. This study offers methodological and empirical insights into how tourism systems respond to severe disturbances, with implications for monitoring and enhancing resilience in tourism-dependent regions exposed to global shocks and market volatility.

To address a significant knowledge gap in chemical ecology underpinning larval settlement processes on coral reefs, we examined the tissue-associated metabolomes using nuclear magnetic resonance (NMR) spectroscopy across 14 species of crustose coralline red algae (CCA) and one non-coralline calcareous red alga collected from the Great Barrier Reef, Australia. We further explored the relationship between algal metabolites and the settlement success of fifteen reef-building coral species across five families, as well as a key coral predator, the crown-of-thorns starfish (CoTS; Acanthaster cf. solaris). We found that algal metabolomes are highly variable and differ among species, phylogenetic lineages, and reef habitats, highlighting the combined influence of evolutionary history and environmental context on algal metabolomes. We also identified strong, positive correlations between specific algal metabolites, particularly disaccharides and trisaccharides (e.g., raffinose, maltose), and glycine betaine with high settlement success in both corals and CoTS. This study provides the most comprehensive analysis to date of coralline algal metabolomes and their ecological significance to coral reef ecosystems. These results provide novel chemical, biological and ecological insights that may be used to inform the optimisation of coral aquaculture techniques for reef restoration, as well as potential strategies for controlling CoTS outbreaks to mitigate ongoing reef decline.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-29875-6.

ABSTRACTUnderstanding the dynamics of range expanding species, particularly those that have effects on recipient reefs, is vital to inform management and conservation strategies. A rare outbreak of the tropical Crown of Thorns seastar (Acanthaster cf. solaris) (COTS) on a subtropical coral reef and a subsequent control program, presented the opportunity to determine the likely origins and number of recruitment events that may have generated this outbreak. The presence of both cosmopolitan and regional mitochondrial haplotypes in this outbreak population indicated larval connectivity via the poleward flowing East Australian Current (EAC) from the Great Barrier Reef (GBR) and Coral Sea. High genetic connectivity with the GBR, based on mitochondrial COI variation, where multiple COTS outbreak events have occurred through time, suggests a high risk of future outbreaks in subtropical eastern Australia. Additionally, levels of COI genetic diversity in the subtropical outbreak population are consistent with either ongoing recruitment or multiple source populations, rather than a new founder population from a single dispersal event. Outbreaks of COTS are likely to become a more frequent occurrence under future climate change scenarios as the poleward‐flowing EAC strengthens and brings warmer waters to subtropical reefs. Agencies that manage subtropical reefs should prepare and plan for future outbreak events and develop policy and management strategies for this range extending species.

Retention of increased maximum oxyregulation capacity in corals transplanted from an extreme mangrove environment to a reef flat.

Analysis of time series data is fundamental in ecology for understanding community dynamics, and the mechanisms driving such dynamics. However, ecological time series commonly contain missing values, which can arise due to methodological changes in monitoring programs, poor weather conditions, logistical constraints, or human error. State-space models are a useful suite of techniques for analyzing ecological time series with missing data. Such models can estimate the unobserved true abundances as latent variables, even for putative census occasions that lack observations. Nevertheless, the impact of missing data on parameter accuracy and precision in these state-space models remains poorly investigated, particularly in species-rich systems. We evaluated the performance of a multivariate process-based state-space model for time series of varying lengths and sampling frequencies, using simulated data informed by empirical counts of reef fish communities from the Great Barrier Reef in Australia. We found that despite containing missing data, the models fitted to longer time series produced more accurate and precise parameter estimates compared to shorter, complete-case time series. Additionally, higher spatial replication with uneven census intervals enhanced parameter precision more than maintaining census frequency at the expense of reducing the number of sites. Analysis of reef fish community data revealed attenuation in intrinsic population growth parameters and weaker intraspecific density dependence when modeling longer time series whose inter-census intervals change, while estimates of variability in species' population growth parameters due to environmental fluctuations remained consistent regardless of sampling design. Nonetheless, analyses of shorter, complete-case time series still produced reliable parameter estimates. Our findings highlight the robustness of Bayesian state-space models to missing data, demonstrating that flexibility in long-term monitoring programs does not compromise ecological inference from these models.

ABSTRACT The red seaweed Asparagopsis taxiformis (common name: red sea plume) is attracting global attention because of its ability to reduce methane emissions in livestock systems. However, its habitat and distribution within the Great Barrier Reef (GBR)—one of the world's most iconic marine ecosystems—remain largely unexplored, posing challenges for conservation and the sustainable development of the seaweed industry. To help bridge this gap, we used habitat suitability modelling to identify areas in the GBR with favourable environmental conditions for A. taxiformis . We combined traditional and community‐contributed data with marine spatial datasets to generate a predictive model using a machine learning approach (MaxEnt). Our findings indicate that A. taxiformis may occupy a broad habitat range along the GBR, spanning nearshore and offshore areas from the northern to southern sectors, albeit with some gaps. These potential habitats include areas with no previous records. Highly suitable habitats were found in areas with water depth of less than 20 m, minimum average seawater velocities of 0.3–0.5 m s −1 , and minimum photosynthetically active radiation levels of 25–28 E m −2 day −1 . Future projections suggest that more areas will become more suitable by 2050, possibly indicating habitat expansion. The identification of unreported potential habitats of A. taxiformis in the GBR provides a foundation for targeted monitoring and adaptive conservation and management strategies at both species and ecosystem levels.

While biological control (or biocontrol) is an established method for managing pest species in terrestrial systems, few successful applications have been reported for marine environments. Crown-of-thorns starfish (CoTS, Acanthaster ssp.) are regarded as a pest species across the Indo-Pacific, where they are voracious predators of corals and represent one of the largest causes of coral mortality on the Great Barrier Reef (GBR). The role of reef fish in moderating outbreaks of CoTS through biocontrol has recently become more widely recognized. Here we have incorporated reef fish into a meta-community model of the GBR to demonstrate the critical role that marine reserves and other fisheries regulations have had in limiting the prevalence of CoTS outbreaks and maintaining the resilience of the GBR ecosystem. Our results suggest that without these interventions, the GBR would have already passed a major tipping point to a new state characterized by few predatory fish, continuous CoTS outbreaks and substantially lower coral cover. Model projections to 2050 demonstrate the importance of maintaining protection into the future and suggest that additional gains can be made over the next decade by continuing to manually control CoTS numbers. However, beyond 2040, the escalating impacts of climate change and the underlying resilience of CoTS populations will limit the effectiveness of interventions based on biocontrol.

Coral bleaching and crown-of-thorns starfish modulate long-term changes in coral cover and composition across reef zones at Lizard Island, northern Great Barrier Reef

Abstract Australia's Great Barrier Reef (GBR) is emblematic of the beauty of coral reefs and the perils they face. Of primary concern is the increasing frequency of mass coral bleaching events, when environmental stressors disrupt the symbiosis between coral host and algal energy source on a major scale. Here, we used four decades of observed environmental variability and bleaching events to calibrate predictors of large‐scale bleaching on the GBR, which included sea‐surface temperature, ocean currents, and light stress. Future bleaching projections were developed from a suite of models in the Coupled Model Intercomparison Project, covering ranges of future emissions scenarios and bleaching sensitivities. For return times between bleaching events to stabilize at three or more years—giving corals any chance of reproducing between bleaching—requires an optimistic scenario of coral sensitivity and either a sustainable future (SSP1) or a “middle of the road” emissions future (SSP2).

ABSTRACT The Great Barrier Reef (GBR) is a globally significant natural wonder, threatened by pollutant loads from eastward-draining rivers. A distributed hydrological model, G2G (Grid-to-Grid), has been configured at a resolution of 0.01° (∼1 km) and 1 hour to simulate these flows. A semi-distributed hydrological model, SWIFT (Short-term Water Information Forecasting Tool), has been set up for 9 catchments at 19 streamflow gauging locations within the same area, as part of the Australian national 7-day Ensemble Streamflow Forecast Service. This provided an important research opportunity to assess the two modelling approaches for different purposes. The performance of both models has been evaluated at the 19 common gauged locations and varies from site to site, but is broadly comparable. The SWIFT is slightly better because it is calibrated to each gauged catchment. In contrast, G2G is configured as a single area-wide model supported by landscape spatial datasets and time-series flow data. G2G is capable of generating outputs for any grid cell, including ungauged locations, whilst SWIFT can only generate outputs at predefined locations on the river network. In conclusion, these catchment-specific and area-wide modelling approaches are compared and their suitability discussed in relation to the modelling purpose.

ABSTRACT Monitoring cetaceans in Australia's Great Barrier Reef (GBR) is essential for understanding their ecological roles and informing conservation, yet traditional visual surveys are limited by logistical constraints. Passive acoustic monitoring (PAM) offers a complementary solution, particularly in acoustically complex coral‐reef habitats of the southern GBR. Over 2 years, we deployed an autonomous recorder at Lady Elliot Island to document cetacean presence and assess environmental associations. We detected vocalizations from humpback whales ( Megaptera novaeangliae ), dwarf minke whales ( Balaenoptera acutorostrata subsp.), and delphinids, likely spinner ( Stenella longirostris ) and/or bottlenose dolphins ( Tursiops spp.). Humpback whale song dominated recordings from June through October, while dwarf minke whale “Star‐Wars” calls occurred from May to August, marking the first acoustic evidence of this subspecies within the southern GBR. Dwarf minke whale detections correlated positively with chlorophyll‐ a concentration, whereas humpback whale detections were negatively associated with wind speed. Rorqual vocalizations declined during periods of elevated anthropogenic noise, while odontocete detections remained unaffected. These results highlight PAM's effectiveness for detecting cetaceans within complex reef soundscapes and suggest acoustic niche partitioning among taxa. These critical baseline data inform management strategies for understudied GBR cetacean populations and establish a robust framework for future long‐term monitoring efforts and effective conservation actions.

On coral reefs, disturbances commonly generate legacy materials in the form of coral rubble. Rubble morphometrics and the diversity of organisms that bind rubble together can influence recovery trajectories. The quantification of rubble movement threshold velocities has been used to predict rubble bed stability, a precursor to binding. Yet empirical data on bind strength across environmental gradients are needed to inform predictions of whether bound rubble beds will experience routine bind breakage, and thus poor recovery, under varying hydrodynamic regimes. Over 18 mo, we tracked the strength of binding organisms that colonised experimental rubble pairs along environmental gradients on the Great Barrier Reef and used strength to estimate breakage velocity thresholds. The degree of contact between rubble pieces was a key determinant of bind strength, which increased over time and was weakest at inshore sheltered sites, driven by a high proportion of macroalgal binds. Bind strength was a direct reflection of the binding community, with the strongest binds by vermetid snails, bivalves, solitary ascidians, hard corals, and crustose coralline algae. For most offshore and inshore exposed sites, the threshold velocity required to break apart bound rubble increased from ~1 m s -1 after 4 mo of stability and binding succession to ~3 m s -1 by 18 mo, though these thresholds will vary with rubble morphology, arrangement and resulting interstitial spacing. These findings can be used in conjunction with time-series hydrodynamic data to predict the potential for disturbed rubble beds to recover and thus optimise the deployment of reef restoration interventions.