Coral Reefs

The endosymbiosis between tropical reef-building corals and dinoflagellate algae (family Symbiodiniaceae) underpins the healthy functioning of coral reef ecosystems. Although dominant host-symbiont pairings differ across spatial scales (e.g., bioregion, reef zone, and depth), corals often associate with multiple symbionts. Where diverse symbionts occur together, their local-scale ecology is poorly understood. Moreover, whilst coral morphological plasticity generates a structurally complex spatial habitat for endosymbiosis, the role of host geometry in facilitating symbiont co-occurrence is completely unexplored. Here, we integrated high-throughput sequencing of the ITS2 gene region with digital 3D photogrammetry to evaluate symbiont distribution within coral structural habitat and determine the influence of host morphology on symbiont community composition. Symbiont composition was characterised along a vertical gradient (coral apex to base) across 50 Hydnophora microconos colonies from Rarotonga, Cook Islands. We identified dominance by the genera Durusdinium and Cladocopium, with inter-genus co-occurrence recognised in 60% of coral colonies. The co-occurrence of two Cladocopium lineages (C3f and C3k) was validated based on congruence with the plastid minicircle psbA non-coding region (psbAncr). Geometric quantification from digital 3D reconstructions of coral colonies revealed that single symbiont taxon colonies were morphologically distinct, whilst multi-symbiont colonies exhibited a broader morphological range. Where Cladocopium-Durusdinium co-occurrence was identified, surface orientation indicated increased Durusdinium prevalence toward the base of coral colonies, corresponding to regions with the highest occlusion of modelled downwelling light. Collectively, these findings suggest that coral structural heterogeneity supports Symbiodiniaceae diversity and highlights the value of resolving microhabitat-level variation to understand symbiont co-occurrence.

The transformative impacts of global bleaching events are now a ubiquitous feature of coral reefs, often resulting in taxonomically simplified coral assemblages that can persist long-term due to ongoing ocean warming, heatwaves, and localized anthropogenic stressors. Understanding to what extent these processes shape symbiont biodiversity continues to be a major knowledge gap. Here, we examined Acropora host and symbiont communities on Kiritimati (Republic of Kiribati), seven and a half years after the 20152016 El Nino-associated marine heatwave, which caused a near total loss of the genus in the atoll's shallow reefs. We quantified Acropora cover and growth-form composition at 37 sites spanning a gradient of local human disturbance and characterised Symbiodiniaceae communities using ITS2 DNA metabarcoding from 109 coral tissue samples at 13 of the sites. Corymbose and tabular Acropora growth forms remained evenly represented across the atoll and cover declined with increasing human disturbance. Symbiodiniaceae communities were dominated by Cladocopium with 93 % of colonies associated with a single ITS2 profile. Communities were homogenous, with low diversity and insignificant differences amongst growth forms, but slight differences across disturbance levels. DNA barcoding of the PaxC intron identified the majority of host colonies as most similar to Acropora granulosa (62 %) and Acropora hyacinthus (24 %). Although dominance by a single symbiont lineage is common among Acropora species across the Pacific, the low Symbiodiniaceae diversity observed at Kiritimati contrasts with the substantial within- and among-lineage diversity documented elsewhere. The depauperate Symbiodiniaceae communities observed in this study may thus represent a lasting legacy of the 2015-2016 disturbance, with the recovering Acropora assemblage representing an early stage of community reassembly drawing from a potentially depleted environmental symbiont pool.

Coral skeletal integrity underpins reef habitat complexity and coastal protection, yet it remains unclear whether corals persisting in chemically variable marginal habitats, such as mangrove-associated reefs, maintain sufficient mechanical resistance to withstand physical disturbance. We combined micro-computed tomography (micro-CT) morphometric analysis with compression testing to quantify skeletal microarchitecture and compressive mechanical performance of Pocillopora sp. skeletons collected across a habitat gradient at Low Isles, Great Barrier Reef, from mangrove-associated sites to exposed reef sites. Baseline skeletal properties varied among sites, with the Proximal Reef site having the densest and least porous skeletons, while mangrove-associated sites had the most porous skeletons. Similarly, Proximal Reef skeletons exhibited two-to-three-fold greater compressive stiffness and peak force than mangrove-associated skeletons. Percentage object volume was a stronger predictor of compressive stiffness than surface area-to-volume (S/V) ratio, indicating that bulk skeletal density better captured load-bearing capacity than surface architectural complexity. Structural failure mode also differed markedly among habitats: mangrove-associated skeletons underwent catastrophic fragmentation of their open, porous framework, whereas Distal and Proximal Reef skeletons failed through discrete crack-plane propagation while largely maintaining overall structural coherence. These results indicate that the physiological stress tolerance associated with mangrove habitats occurs alongside reduced mechanical resistance and more destructive failure modes, suggesting a potential trade-off between chemical stress tolerance and structural investment. Assessments of resilience in marginal coral populations should therefore consider skeletal mechanical performance alongside physiological tolerance, particularly as climate change intensifies storms and alters hydrodynamic disturbance regimes.

The genus Phakellia comprises predominantly fan-shaped deep-sea sponges, but its species diversity and boundaries remain unresolved. Here, we use an integrative approach combining morphological and molecular data to investigate the Phakellia robusta species complex and describe two new species, Phakellia pallida sp. nov. and Phakellia pusilla sp. nov. Overlap in external and spicular morphology makes these taxa challenging to identify. Molecular analyses based on mitochondrial (cox1) and nuclear (28S) markers support the recognition of the three taxa as distinct species, and reveal their close evolutionary relationship. The two new species co-occur in the NE Atlantic Ocean and the Mediterranean Sea, with overlapping depth ranges, although P. pallida sp. nov. is generally found at greater depths. Our results also suggest that several previous records of P. robusta from the Mediterranean and southern parts of the NE Atlantic may instead correspond to either P. pallida sp. nov. or P. pusilla sp. nov., indicating that its distribution requires reassessment. In addition, a group I intron previously reported in the cox1 gene of P. robusta was polymorphically detected at the same insertion site in some, but not all, individuals of P. pusilla sp. nov., but it was absent from P. pallida sp. nov. individuals. Overall, our results reveal pseudocryptic diversity within Phakellia and highlight the value of integrative approaches for resolving species boundaries and reassessing deep-sea sponge diversity and distributions.

1. Protecting and restoring corals is critical to conserve marine biodiversity and ecosystem services in the Anthropocene. Knowledge of coral larval dispersal dynamics can be used to identify important sites for coral metapopulation connectivity and to spatially optimise coral conservation efforts. However, we know little regarding the larval dispersal of many coral species and our understanding of the relationships between coral larval dispersal and life-history traits (e.g., reproductive mode, colony morphology), phylogenetic relationships, and biogeography is incomplete. These knowledge gaps impede coral conservation. 2. In this research, we systematically reviewed the species, regions, and methodologies of studies of coral larval dispersal. Additionally, we conducted a meta-analysis to quantify the heterogeneity in reported coral larval duration values and identified the roles of life-history traits in driving that heterogeneity. 3. We found that various methods (experimental, biophysical modelling, and population genetics) were used to study 221 coral species across many regions. Soft and temperate corals received comparatively lower research attention. Our meta-analysis reveals that reproductive mode and colony morphology explain significant heterogeneity in larval settlement times, and that closely-related species have more similar larval settlement times. 4. Our findings suggest that reproductive mode and colony morphology could be used to predict larval duration in under-studied coral species, and that larval duration could be approximated from closely-related corals when trait data is unavailable. Our results support strategies focused on modelling differing larval durations across corals with different life-history traits to predict realised dispersal in under-studied coral species and identify conservation priority sites.

The identification and use of stress-tolerant coral in outplanting efforts has been proposed as a method of restoring and bolstering reef health under increasing environmental change. Prior research has focused on understanding survival in cross-reef transplantation, but evidence of long term resiliency of outplanted corals remains limited. Here, we report data at a five-year timepoint of a reciprocal transplant study of the stress-tolerant Caribbean corals Pseudodiploria strigosa and Siderastrea siderea between a nearshore and offshore site in Belize. Extreme marine heat wave conditions in August of 2024 revealed species and site-specific bleaching patterns. Through assessments of mortality, energy reserves, and chlorophyll concentrations, P. strigosa appear to be more limited in long-term acclimatization potential to the nearshore environment while S. siderea maintain acclimatization capacity displayed 17 months post transplant to nearshore. This work conveys information relevant to managers in selecting species for restoration efforts based on short-term growth and long-term resilience in native versus non-native sites, offers insight into potential mechanisms driving these trends, and takeaways on site specific management decisions for successful coral outplanting success.

The increased frequency and intensity of coral bleaching events expose reefs to disturbance-recovery cycles that threaten their long-term dynamics. Understanding the impact of thermal stress requires evaluating coral mortality and recovery rates after disturbances. By integrating two long-term monitoring datasets, we examined coral mortality and recovery patterns at 13 sites in Mo'orea, French Polynesia, following the 2019 bleaching event, the most severe heat stress on record for the island. The maximum accumulated heat stress (AHSmax) varied from 5.76 to 6.26 {degrees} C weeks and enabled a direct analysis of heat-stress-related mortality. One year after bleaching, Pocillopora mortality increased with AHSmax, reducing mean coral cover from 35% to 17%. Regardless of AHSmax, Acropora mortality was high at all sites (median: 84%), reducing mean cover from 5% to 1% and indicating greater heat tolerance of Pocillopora than Acropora. Within four years after the bleaching event, no recovery occurred, and coral cover further declined relative to pre-bleaching levels. This decline was stronger for sites exposed to more intense heat stress. The impact of colony size was assessed by tracking 3090 individual Pocillopora colonies over six years and estimating size-dependent mortality and growth with a Bayesian mixed model. Immediately after the bleaching event, large Pocillopora corals exhibited a higher probability of complete and partial mortality than smaller colonies, highlighting size-specific consequences of bleaching. Even three years after the heat stress ended, large Pocillopora corals remained stressed, as evidenced by the continuously high probability of partial mortality. The lack of recovery observed here may be related to increased spatial competition with macroalgae. The disappearance of large fecund colonies and high mortality of coral recruits could have catastrophic consequences for the resilience of Mo'orea's reefs.

Marine heatwaves cause widespread coral bleaching and mortality, yet thermal responses often differ between adult and juvenile corals, with the latter frequently being more tolerant. Whether the observed enhanced tolerance of juveniles reflects intrinsic physiological differences across life stages or simply reduced environmental stress due to shaded microhabitats occupied by juveniles, or a combination of both factors, remains unclear. To test whether colony size determines thermal responses and if a threshold size exists for tolerance, we exposed 89 colonies of the reef-building coral Acropora aff. digitifera to a 6-week, 32.5 C simulated marine heatwave under controlled light conditions, with cumulative stress reaching 20 C-weeks. Contrary to expectations, ~2 C-weeks less heat stress was required to trigger bleaching and mortality in coral juveniles compared to adults. Mortality divergence across colony sizes was greatest at ~10 C-weeks, when the smallest corals exceeded 80% mortality, whereas the largest colonies showed <10% mortality. A breakpoint in survival odds was apparent at 13.4 cm diameter, corresponding to the size at onset of sexual maturity in the native wild population for this species. These results indicate an ontogenetic shift in physiological heat tolerance, with larger reproductively mature colonies showing enhanced tolerance. The apparent survival advantage of juveniles in the reef frequently reported during bleaching events could be more likely due to micro-environmental buffering than intrinsic physiological tolerance. Our findings suggest that juvenile corals may be more vulnerable to climate change than previously thought, particularly as declining habitat complexity could reduce microhabitat refugia on future reefs.

Climate change is threatening coral reef ecosystems around the world, causing significant declines in reef organisms, including sponges. The health of sponges is intimately linked to their symbiosis with microorganisms, yet little is known about their integrated response to ocean warming. Here, we present a comprehensive view of the effect of elevated sea surface temperatures (SST) on the model sponge Ianthella basta. I. basta individuals were exposed to temperatures up to 32 {degrees}C, 2-3 {degrees}C above the mean annual maxima. Host gene expression profiles showed an initial response to heat stress after 2 days, and a decreased expression of genes involved in maintaining tissue integrity, pumping capacity, vitamin transport, and stable symbioses after 4 to 8 days. Congruently, heat stressed samples started to show tissue regression and a reduced abundance of the dominant symbionts after 4 days. A significant loss of the symbionts occurred after 8 days, together with a reduction in microbially driven nitrogen cycling and amino-acid transport and an introduction of opportunistic microbes, which could lead to nutrient imbalance and further destabilisation of the holobiont. Together, this work provides important insights into the avenues through which future SST can impact host-microbe interactions in coral reef sponges.

Mesophotic coral ecosystems are commonly interpreted as thin biological veneers over relict shallow-water reef structures, but their capacity to generate late Holocene carbonate deposits remains poorly quantified. Here we combine diver excavations, rubble-bed thickness surveys, radiocarbon age-depth modelling, sediment grain-size analyses, coral-rubble assemblages, trace-element geochemistry, and modern Alveopora allingi growth measurements from two 40-65 m deep coral-rubble fields in the northern Gulf of Eilat/Aqaba, Red Sea. Rubble deposits are at least 1.0-1.5 m thick and accumulated at mean rates of 2.21 {+/-} 0.52 mm yr-1 at the Dekel site and 1.33 {+/-} 0.13 mm yr-1 at the IUI site, implying persistent carbonate accumulation over centuries to >1 kyr. Age-depth models indicate quasi-continuous deposition despite pronounced faunal changes, including a shift from A. allingi-dominated rubble to upper layers enriched in Euphyllia paradivisa at Dekel. The dominant modern rubble-forming coral, A. allingi, extends at 3.04 {+/-} 0.87 mm yr-1 and has skeletal density of 1.17 {+/-} 0.27 g cm-3. First-order cover-based accretion estimates at present coral cover fall well below the radiocarbon-derived rates, indicating that long-term mesophotic rubble accumulation integrates historical cover, secondary calcification and sediment retention rather than present live coral cover alone. These data demonstrate that mesophotic rubble fields can act as active carbonate factories and palaeoecological archives, challenging the assumption that modern mesophotic habitats are geomorphologically passive.

Reef fish assemblages in the Veracruz Reef System National Park (VRSNP) are strongly structured along a pronounced north-south gradient, where environmental conditions, urban proximity, and protection levels interact to shape functional diversity and ecosystem functioning. This gradient creates contrasting ecological conditions between northern and southern reefs, providing a natural framework for evaluating how spatial variation influences resilience. Using a stationary visual census across ten reefs distributed latitudinally, we quantified functional entities based on six ecological traits and calculated functional richness, redundancy, over-redundancy, vulnerability, specialization, and originality. A two-way permutational ANOVA and redundancy analysis were used to detect spatial and temporal patterns and to link functional indices with environmental features. The southern sector displayed the most intense functional shifts. Nearshore southern reefs, strongly exposed to sedimentation, nutrient loading, and physical disturbance, exhibited reduced functional richness, fewer functional entities, and high functional vulnerability, indicating strong environmental filtering. Over time, these reefs shifted toward generalist-dominated assemblages with rising redundancy, suggesting functional convergence. In contrast, southern offshore reefs supported higher taxonomic and functional richness, buffered by greater habitat complexity and distance from shore, although they showed declining redundancy, likely reflecting sensitivity to regional climatic disturbances. In the northern sector, the gradient was moderated by effective protection, which reshaped functional configurations. Nearshore protected reefs such as Isla Sacrificios and Isla de Enmedio maintained high redundancy, low vulnerability, and high biomass of large-bodied fishes, resembling offshore systems rather than disturbed southern nearshore reefs. The northern offshore reef (Isla Verde) shared some of these attributes but exhibited temporal declines in richness, signaling emerging vulnerabilities along the gradient. Functional originality and specialization aligned with benthic states across the gradient, particularly where macroalgal or calcareous substrates prevailed. Overall, the north-south gradient is the primary axis of functional organization in VRSNP, revealing that resilience emerges from the interplay among reef geomorphology, urban influence, and governance effectiveness.

Sea turtle conservation relies largely on the identification of ecologically significant marine areas. Green sea turtles (Chelonia mydas) are resident in Aotearoa New Zealand waters, yet much of their spatial ecology remains undefined. To address this, satellite telemetry was used to map juvenile and sub-adult green sea turtle spatial movements, residency patterns, and habitat associations. Our findings provide the first evidence of individual fine-scale habitat use and long-term residency in New Zealand waters. Data will contribute to regional and global efforts to identify ecologically significant sea turtle habitat, including Important Marine Turtle Areas (IMTAs) and Blue Corridors for Turtles (BC4T), and help advance conservation efforts.

Understanding the consequences of global change for our ecosystems requires reliable, accurate, and scalable tools for detecting ecological change. To this end, recent efforts have focused on scaling up the quantification of demographic processes from individual organisms (the fundamental ecological unit) to the larger spatial scales they inhabit to yield more precise and informative estimations of ecological change, especially in response to disturbance. Here, we describe a transferable workflow that combines robust underwater photogrammetry techniques with machine-learning-assisted image analysis to quantify demographic changes in coral colonies (growth, stasis, partial mortality, and complete mortality) through time on the reef landscape. We then demonstrate several analytical applications of this workflow that can be broadly applied to sessile and/or clonal organisms in other ecosystems. First, we tracked the fates of 3,162 coral colonies through a marine heatwave that caused substantial mortality. Second, our approach enabled detection of size- and taxon-dependent patterns in demographic changes from before to after the heatwave. Finally, for a subset (425) of these colonies, we further demonstrated how our method can be used to track fates across multiple years, including a year of change before and after the heatwave took place, revealing nuanced patterns of survival and mortality, as well as changes in size structure that occurred before and after the disturbance. Our workflow offers an important advance for increasing the accuracy of change detection on coral reefs and other ecosystems by linking demographic changes in individual organisms with spatially extensive image-based surveys through time.

Metabolic rate governs the pace of life through the allocation and expenditure of energy, yet metabolic rate data are unavailable for most species. External morphological traits, such as gill slits, have been used to infer respiratory physiology and metabolism in sharks, yet, whether that pattern is generalizable across rays is unknown. In rays (Batoidea), spiracle length seems adaptive to oxygen uptake capacity, environmental oxygen availability, and activity level. Thus, we evaluate the allometry of external respiratory morphology (spiracles and gill slits) in rays using 550 museum specimens representing 88 species. We test whether spiracle length and gill slit height grow isometrically with body size (total length or disc width) within and across species. Overall, we find spiracles and gill slits are morphologically diverse, varying widely in shape within and between families. Spiracle length and gill slit height scale isometrically and are a consistent proportion of body size, despite such high morphological variability. While that proportion is consistent through ontogeny, each species proportion differs (e.g. gill slit height ranges from 0.93% of total length in Spotted Legskate to 2.93% in Pacific Electric Ray). Of the three swimming styles, pectoral oscillating species (Mobulid and Eagle Rays) may have steeper scaling of spiracle length with gill slit height - consistent with greater respiratory capacity in species with more active lifestyles. Our findings are consistent with literature hypothesizing external respiratory morphology (spiracles and gill slits) is tightly related to metabolic rate and activity level, and demonstrate the value of natural history collections in ecological research. Importantly, the isometry of both respiratory traits means that a single measure of any individual, irrespective of size, will be representative of the species thus providing a basis for expanding our understanding of metabolic morphology, enabling future work on life history, extinction risk, and ecological function.

Disturbances alter ecosystem resilience by killing organisms and leaving behind material legacies. We tested how material legacies from marine heat waves and cyclones govern transitions between coral- and seaweed-rich states on tropical reefs. Heat waves kill coral tissue but leave their skeletons to erode gradually, whereas cyclones scour away emergent biota. Field experiments revealed that dead skeletons protect seaweeds from herbivory, catalyzing a transition to a seaweed-rich state that becomes self-sustaining after skeletons disappear. After four years, 73% of skeleton-added (heat wave) plots transitioned to seaweeds compared to 0% of scoured (cyclone) plots that lacked skeletons, while 87% of seaweed-rich plots scoured to simulate a cyclone stayed seaweed-free. Reef trajectories after natural disturbances were similar: four years after heat wave-induced coral mortality, 63% of time-series plots had transitioned to seaweeds with none recovering to coral; four years after a cyclone removed skeletons from a prior disturbance, none had transitioned to seaweeds and 60% had returned to coral. A disturbance not only can displace an ecosystem state, it can rapidly reshape the resilience landscape through the material legacies it creates or removes. Our findings also show that successive disturbances need not have cumulative negative effects: after a reef is driven into a seaweed-rich state, a cyclone can act as a rescue disturbance by removing established seaweeds and, when structural refugia are also removed, shrinking the seaweed stability domain. By reshaping resilience through contrasting material legacies, disturbance type and sequence can be as important as frequency and severity in determining ecosystem trajectories.

Zoos and public aquariums serve as essential hubs for wildlife conservation, public education, and scientific research; however, the success of these missions depends upon maintaining high animal welfare standards despite constant human presence. A primary concern is the 'visitor effect': the alteration of animal behavior due to human presence. While this phenomenon is well-documented in captive mammals and has been explored in chondrichthyes, it remains largely unexamined in teleost fish, despite evidence of their sensitivity to human stimuli in natural environments. This study addresses this knowledge gap by investigating the behavioral responses of 13 teleost species to varying levels of crowd density, direct human solicitation, and ambient noise. Our multivariate analysis reveals that visitor density and visitor-induced disturbances are significant drivers of behavioral change, with species identity acting as the primary source of variance. We observed high inter-taxonomic variability: while several species (including Euxiphipops sextriatus, Dascyllus aruanus, and Zebrasoma flavescens) showed marked sensitivity through significant alterations in stress-coping, exploration, and aggression, others remained behaviorally stable. Furthermore, acoustic analysis indicates a complex soundscape where visitor density correlates with increased sound amplitude, particularly in the 100 Hz to 400 Hz range, a critical band for teleost hearing suggesting that visitor-induced noise is distinct from the aquarium's technical background noise. These findings underscore that the 'visitor effect' is not a uniform phenomenon but a complex interaction shaped by species-specific sensitivity and distinct anthropogenic stressors. Our results highlight the necessity of incorporating species-specific behavioral data and acoustic monitoring into welfare management protocols to better mitigate the impact of human presence on captive fish populations.

While the influence of microorganisms in the thermal physiology of animals is increasingly recognised, the role of the gut microbiome in enhancing phenotypic plasticity remains underexplored, particularly in ectotherms. Here, we tested the effect of gut microbiomes in modulating the physiological response of lizards to sudden temperature fluctuations. In captivity, we conducted an experiment with wild-caught Podarcis lizards: Mediterranean Podarcis liolepis (n=9) adapted to warm and dry environments, and Atlantic P. muralis (n=18) adapted to cooler and wetter conditions. Animals were assigned to three groups (intervention, control-cold and control-warm) and subjected to microbiota manipulations using antibiotics and faecal microbiota transplants (FMT). In the intervention group, cold-adapted P. muralis received faecal suspension from warm-adapted P. liolepis, while control-cold and control-warm groups received intraspecific transplants. Microbiome variation was analysed through genome-resolved metagenomics of 162 faecal samples, yielding 313 MAGs across 15 phyla, containing almost 1M annotated genes. One week after transplantation, microbiomes of control animals differed from their original state, whereas those of the intervention group (P. muralis), transitioned to a state resembling P. liolepis. After two weeks, both control groups showed trends of reversing their microbiomes to their original states. However, the intervention group displayed a distinct trajectory, resembling the microbial donors'. Although potentially relevant trends were observed, these microbiome alterations did not translate into detectable significant differences in their thermal physiology. Nevertheless, our results provide proof of concept for microbial transplants in lizards, and opportunities to further explore the link between gut microbes and host physiological responses in ectotherms.

Schooling is a widespread behaviour among pelagic fish that reduces locomotion costs of migration and predation risk. It is characterised by coordinated movements, speed and orientation of group members. Although schooling can vary both between populations and among individuals of the same population, these levels of variation are seldom considered together. Here, we investigated whether schooling tendencies in three-spined sticklebacks (Gasterosteus aculeatus) vary between populations and among individuals within-populations depending on their phenotype. We first compared the schooling behaviour of anadromous (migrants) and recently landlocked (residents) populations and tested whether individual sociability explained within-population variation in schooling. We then studied whether schooling behaviour is modulated when migrants and residents are in mixed groups. Migrant groups displayed better schooling performance than residents with higher alignment. Within migrant groups, less social individuals displayed more leadership, were better aligned, swam closer to others and fatigued less than more social fish. These patterns were absent in residents. When the two populations were mixed, overall schooling performance declined, particularly in migrants, with schools exhibiting reduced compaction and alignment, resembling resident groups. Thus, individuals did not modulate their schooling behaviour to the group social composition and phenotype-dependent schooling patterns were disrupted in migrants when mixed. These findings suggest that migration-related behaviours can disappear quickly post-isolation. They also highlight the importance of individual sociability in self-organisation and shaping collective behaviour, especially in populations that retain migratory behaviour. Considering behavioural variation across multiple hierarchical levels is thus key to understanding complex social systems.

Extreme climate events are rapidly reshaping ecosystems and contributing to biodiversity loss, yet their long-term impacts remain poorly understood, particularly in marine systems. In 2011, an unprecedented marine heatwave (MHW) on the west coast of Australia drove declines in habitat-forming plants and across taxa spanning multiple trophic levels. Shark Bay, home to an iconic Indo-Pacific bottlenose dolphin (Tursiops aduncus) population, endured temperatures 3-5{degrees}C above long-term means, triggering catastrophic seagrass loss. Using 20 years (2003-2023) of dolphin photo-identification data, we fitted a Bayesian Hidden Markov Model to estimate annual, age-class specific survival probabilities, abundance and recruitment rate, and their association with MHW-mediated seagrass loss in the western (WSB) and eastern (ESB) gulfs of Shark Bay. Adult survival declined markedly, from 0.99 (0.98-1.00) pre-MHW to 0.85 (0.79-0.90) post-MHW in WSB, and from 0.96 (0.92-0.98) to 0.89 (0.85-0.95) in ESB, remaining below pre-MHW levels for several years, while juvenile and calf survival declined in both gulfs to a lesser extent. Recruitment declined in both gulfs and, although recovery was evident in WSB from 2019 onward, continued to decline in ESB until the end of the study. These sustained demographic declines drove substantial reductions in population growth and abundance in both WSB (39%) and ESB (36%). Demographic changes were associated with seagrass loss, here a proxy for habitat and prey availability, with clearest support for adult survival in WSB and a two-year-lagged recruitment response in ESB. This pathway is likely to operate across diverse ecosystems as climate change drives increasing loss of habitat-forming species. The severity and duration of these demographic impacts illustrate that habitat change can cascade through trophic systems to overwhelm demographic resilience in upper-trophic species. This has negative implications for even long-lived, K-selected species, whose slow demographic recovery may not keep pace with the accelerating frequency and intensity of climate disturbance.

Fledglings of burrow-nesting seabirds are vulnerable to disorientation by artificial light at night (ALAN) and grounding in coastal human settlements, where most individuals presumably perish if not rescued. Accurate estimates of the effects of stranding on seabird populations remain elusive due to several levels of uncertainty, such as the number of stranded seabirds estimated to remain undiscovered by rescuers. One species subjected to stranding is the Atlantic puffin (Fratercula arctica). We hypothesized that the detection probability of puffin fledglings by the Puffin Patrol rescue program, operating in Newfoundland, Canada, is affected by light level, concealment level, and search effort. We deployed realistic puffin decoys in locations of varying light and concealment levels throughout two sites that are searched nightly by rescuers and measured the amount of time and search effort required until each decoy was found. Approximately 78% more search effort was required to find a decoy in darkness (32.0 min) compared with illuminated conditions (18.0 min), and up to 100% more search effort was required to find a decoy placed in concealed conditions (35.5 min) than one in the open (17.5 min). After two hours of searching, on average over 10% of decoys were still not found, although each additional minute of search effort increased detection rate of an individual decoy by 0.6%. In combination with recent advances in our knowledge of seabird post-stranding behaviour, our study offers a first step in the development of correction factors which can be adapted to site- and species-specific requirements of other rescue programs around the world that rely on volunteers to search for stranded birds. Application of such correction factors will hopefully result in better estimation of mortality rates and their resultant effects on populations.