Deep heat: a comparison of water temperature, anemone bleaching, anemonefish density and reproduction between shallow and mesophotic reefs

French Polynesia is experiencing increasing coral bleaching events in shallow waters triggered by thermal anomalies and marine heatwaves linked to climate change, a trend that is replicated worldwide. As sea surface thermal anomalies are assumed to lessen with depth, mesophotic deep reefs have been hypothesized to act as refuges from anthropogenic and natural disturbances, the ‘deep reef refugia hypothesis’ (DRRH). However, evidence supporting the DRRH is either inconclusive or conflicting. We address this by investigating four assumptions of the DRRH focusing on the symbiotic association between anemones and anemonefish. First, we compare long-term temperature conditions between shallow (8 m) and mesophotic sites (50 m) on the island of Moorea from 2011–2020. Second, we compare the densities of the orange-fin anemonefish, Amphiprion chrysopterus between shallow and mesophotic (down to 60 m) reefs across three archipelagos in French Polynesia. Finally, we compare the percentage of anemone bleaching, as well as anemonefish reproduction, between shallow and mesophotic reefs. We found that the water column was well mixed in the cooler austral winter months with only a 0.19 °C difference in temperature between depths, but in the warmer summer months mixing was reduced resulting in a 0.71–1.03 °C temperature difference. However, during thermal anomalies, despite a time lag in warm surface waters reaching mesophotic reefs, there was ultimately a 1.0 °C increase in water temperature at both 8 and 50 m, pushing temperatures over bleaching thresholds at both depths. As such, anemone bleaching was observed in mesophotic reefs during these thermal anomalies, but was buffered compared to the percentage of bleaching in shallower waters, which was nearly five times greater. Our large-scale sampling across French Polynesia found orange-fin anemonefish, A. chrysopterus, in mesophotic zones in two high islands and one atoll across two archipelagos, extending its bathymetric limit to 60 m; however, orange-fin anemonefish densities were either similar to, or 25–92 times lower than in shallower zones. Three spawning events were observed at 50 m, which occurred at a similar frequency to spawning on shallower reefs at the same date. Our findings of thermal anomalies and bleaching in mesophotic reefs, coupled with mainly lower densities of anemonefish in mesophotic populations, suggest that mesophotic reefs show only a limited ability to provide refugia from anthropogenic and natural disturbances

Adaptive effects of parental and developmental environments on offspring survival, growth and phenotype

1. Phenotypic adjustments to environmental variation are particularly relevant to cope with putative environmental mismatches often imposed by natal dispersal. 2. We used an intergenerational cross-transplant field-based experiment to evaluate the morphological and physiological effects of parental and postsettlement water flow environments on the orange-fin anemonefish Amphiprion chrysopterus through ontogeny (at pre- and postsettlement stages). 3. Offspring born from parents under high water flow had an 18% higher caudal fin aspect ratio (a compound measure of shape) at the presettlement stage, 10% slower growth after settlement, and 55% lower survival after settlement compared to offspring from low water flow parents. At the presettlement stage, caudal fin length was determined by parental caudal fin length. At the postsettlement stage, fish survived equally well with similar phenotypes in both high and low developmental flow environments. However, results suggest potential developmental phenotypic plasticity in caudal fin length, which increases more under low water flow during development. After settlement, growth was the only morphological or physiological trait that was associated with parental water flow, which was lower from parents under high flow, as was survival. 4. These results give important insights into the parental contribution, both genetic and nongenetic, in determining early offspring phenotype and subsequent growth and survival. Our results also suggest that offspring may possess flexibility to cope with a wide range of local environments including those different from their parents. Overall, the findings of this study show the fitness consequences of living in different environments and the likely trade-offs between parental and offspring fitness in a wild population

Physiological and behavioural effects of anemone bleaching on symbiont anemonefish in the wild

1. Climate change causes extreme heat waves that have induced worldwide mass coral bleaching. The impacts of temperature‐induced bleaching events on the loss of algal endosymbionts in both corals and anemones are well documented. However, the cascading impacts of bleaching on animals that live in association with corals and anemones are understudied. 2. We performed a field‐based experiment to investigate how host anemone bleaching affected the metabolic rate, growth, behaviour and survival of wild juvenile orange‐fin anemonefish Amphiprion chrysopterus over 1, 2 and (for survival) 9 months. 3. We found that the standard metabolic rate of anemonefish residing in bleached anemones decreased over time but was unaffected in fish from healthy anemones. Despite the reduced metabolic cost, the growth rate of fish from bleached anemones was significantly lower compared to fish from healthy anemones, suggesting that animals residing in bleached hosts are at an energetic disadvantage. This was corroborated by our finding that fish from bleached anemones spent more time out of their anemones, suggestive of a greater need to forage in the water column. However, fish from bleached anemones were overall less active and used less space around the anemone, resulting in a negative correlation between space use and survival after 4 weeks. 4. Our results provide insight into the physiological and behavioural effects of host bleaching on juvenile fish in the wild, and highlight how relatively short‐term thermal anomalies can have long‐lasting impacts beyond the bleached anemones or corals themselves

Capture and discard practises associated with an ornamental fishery affect the metabolic rate and aerobic capacity of three-striped dwarf cichlids Apistogramma trifasciata

Fishing causes direct removal of individuals from wild populations but can also cause a physiological disturbance in fish that are released or discarded after capture. While sublethal physiological effects of fish capture have been well studied in commercial and recreational fisheries, this issue has been overlooked for the ornamental fish trade, where it is common to capture fish from the wild and discard non-target species. We examined metabolic responses to capture and discard procedures in the three-striped dwarf cichlid Apistogramma trifasciata, a popular Amazonian aquarium species that nonetheless may be discarded when not a target species. Individuals (n = 34) were tagged and exposed to each of four treatments designed to simulate procedures during the capture and discard process: 1) a non-handling control; 2) netting; 3) netting +30 seconds of air exposure; and 4) netting +60 seconds of air exposure. Metabolic rates were estimated using intermittent-flow respirometry, immediately following each treatment then throughout recovery overnight. Increasing amounts of netting and air exposure caused an acute increase in oxygen uptake and decrease in available aerobic scope. In general, recovery occurred quickly, with rapid decreases in oxygen uptake within the first 30 minutes post-handling. Notably, however, male fish exposed to netting +60 seconds of air exposure showed a delayed response whereby available aerobic scope was constrained <75% of maximum until ~4–6 hours post-stress. Larger fish showed a greater initial increase in oxygen uptake post-stress and slower rates of recovery. The results suggest that in the period following discard, this species may experience a reduced aerobic capacity for additional behavioural/physiological responses including feeding, territory defence and predator avoidance. These results are among the first to examine impacts of discard practises in the ornamental fishery and suggest ecophysiological research can provide valuable insight towards increasing sustainable practises in this global trade

Guidelines for reporting methods to estimate metabolic rates by aquatic intermittent-flow respirometry

Interest in the measurement of metabolic rates is growing rapidly, because of the importance of metabolism in advancing our understanding of organismal physiology, behaviour, evolution and responses to environmental change. The study of metabolism in aquatic animals is undergoing an especially pronounced expansion, with more researchers utilising intermittent-flow respirometry as a research tool than ever before. Aquatic respirometry measures the rate of oxygen uptake as a proxy for metabolic rate, and the intermittent-flow technique has numerous strengths for use with aquatic animals, allowing metabolic rate to be repeatedly estimated on individual animals over several hours or days and during exposure to various conditions or stimuli. There are, however, no published guidelines for the reporting of methodological details when using this method. Here, we provide the first guidelines for reporting intermittent-flow respirometry methods, in the form of a checklist of criteria that we consider to be the minimum required for the interpretation, evaluation and replication of experiments using intermittent-flow respirometry. Furthermore, using a survey of the existing literature, we show that there has been incomplete and inconsistent reporting of methods for intermittent-flow respirometry over the past few decades. Use of the provided checklist of required criteria by researchers when publishing their work should increase consistency of the reporting of methods for studies that use intermittent-flow respirometry. With the steep increase in studies using intermittent-flow respirometry, now is the ideal time to standardise reporting of methods, so that - in the future - data can be properly assessed by other scientists and conservationists

The potential of bioorthogonal chemistry for correlative light and electron microscopy: a call to arms

Bio-organic Synthesi

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BACKGROUND Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent effects on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. These estimates are particularly important following large-scale mortality spikes, such as the COVID-19 pandemic. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of death globally and over time, providing a nuanced understanding of the effect of these causes on global populations. METHODS The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 cause-of-death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 until 2021. The analysis used 56 604 data sources, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model-a modelling tool developed for GBD to assess the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific mortality estimates-with alternative strategies adapted to model causes with insufficient data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2·5th and 97·5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We also used the coefficient of variation and the fraction of population affected by 90% of deaths to highlight concentrations of mortality. Findings are reported in counts and age-standardised rates. Methodological improvements for cause-of-death estimates in GBD 2021 include the expansion of under-5-years age group to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of COVID-19 and other pandemic-related mortality-which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis. For this analysis, 199 new country-years of vital registration cause-of-death data, 5 country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds. FINDINGS The leading causes of age-standardised deaths globally were the same in 2019 as they were in 1990; in descending order, these were, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94·0 deaths (95% UI 89·2-100·0) per 100 000 population. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke to the third-leading and chronic obstructive pulmonary disease to the fourth-leading position. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271·0 deaths [250·1-290·7] per 100 000 population) and Latin America and the Caribbean (195·4 deaths [182·1-211·4] per 100 000 population). The lowest age-standardised death rates from COVID-19 were in the high-income super-region (48·1 deaths [47·4-48·8] per 100 000 population) and southeast Asia, east Asia, and Oceania (23·2 deaths [16·3-37·2] per 100 000 population). Globally, life expectancy steadily improved between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy showed the positive effect that reductions in deaths from enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others have contributed to improved survival over the study period. However, a net reduction of 1·6 years occurred in global life expectancy between 2019 and 2021, primarily due to increased death rates from COVID-19 and other pandemic-related mortality. Life expectancy was highly variable between super-regions over the study period, with southeast Asia, east Asia, and Oceania gaining 8·3 years (6·7-9·9) overall, while having the smallest reduction in life expectancy due to COVID-19 (0·4 years). The largest reduction in life expectancy due to COVID-19 occurred in Latin America and the Caribbean (3·6 years). Additionally, 53 of the 288 causes of death were highly concentrated in locations with less than 50% of the global population as of 2021, and these causes of death became progressively more concentrated since 1990, when only 44 causes showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles. INTERPRETATION Long-standing gains in life expectancy and reductions in many of the leading causes of death have been disrupted by the COVID-19 pandemic, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period. Each of the seven GBD super-regions showed an overall improvement from 1990 and 2021, obscuring the negative effect in the years of the pandemic. Additionally, our findings regarding regional variation in causes of death driving increases in life expectancy hold clear policy utility. Analyses of shifting mortality trends reveal that several causes, once widespread globally, are now increasingly concentrated geographically. These changes in mortality concentration, alongside further investigation of changing risks, interventions, and relevant policy, present an important opportunity to deepen our understanding of mortality-reduction strategies. Examining patterns in mortality concentration might reveal areas where successful public health interventions have been implemented. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere. FUNDING Bill & Melinda Gates Foundation

Déterminants parentaux et environnementaux des traits associés à la dispersion larvaire et de la physiologie post-installation

Environmental changes induced by human activities impact marine and terrestrial ecosystems worldwide. While facing these perturbations, species may respond in a variety of ways, including migration to a more suitable habitat via dispersal, acclimation via phenotypic plasticity or adaptation via genetic changes. The main opportunity for dispersal in sedentary marine organisms such as coral reef fish is the pelagic larval phase, during which larvae journey in open water before settling onto a suitable habitat. Marine larval dispersal depends on physical factors, such as ocean currents, but is also largely determined by biological larval traits, such as physiology, behaviour and morphology. However, in which way offspring traits associated to dispersal are influenced by either their local environment or their parental legacy, remains less well studied. After larval settlement, phenotypes can still be affected by environmental stressors and thus it is vital to also understand their ability to acclimate to environmental stressors induced by human activities. To answer these questions, I used the orange fin anemonefish Amphiprion chrysopterus as a model species and combined in situ and laboratory analyses. First, by using laboratory reared larvae of wild spawned eggs I explored the influence of maternal size on dispersal-associated traits throughout ontogeny (swimming performance and body size) and demonstrated that larger mothers produce larvae that swim faster (Chapter 2). Then, I investigated how anemonefish parental environmental conditions, such as anemone habitat size (proxy of habitat quality and degradation) affect offspring phenotype (i.e. egg size, larval size and larval swimming performance) and found that parents living in larger habitats produce larger eggs (Chapter 3). In addition, I explored the transgenerational and developmental effects of water flow regimes on larval and juvenile morphology, physiology and survival. Results show that early life survival can be affected by the water flow regime that their parents live in, suggesting differential investment (Chapter 4). In the last part of the thesis I focused on the direct effects of chronic exposure to environmental stressors, such as anemone bleaching (Chapter 5) and artificial light at night (ALAN, Chapter 6) on juvenile A. chrysopterus phenotypes and survival in the wild. I demonstrated that anemone bleaching affects the physiology and behaviour of fish and that both bleaching and ALAN reduce fish growth but not survival, suggesting that wild fish may trade-off growth with survival, even though reduced growth at early stages may have life-long fitness effects. The results of this PhD provide a better understanding of the origin of the variability in the factors influencing the dispersal process as well as the post-settlement phenotype in an iconic coral reef fish. This knowledge may help to better predict how fish populations will respond to climate change. Such predictions are key to mitigating the impacts of climate change and improving the conservation strategies, for example by targeting the most important marine areas and fish phenotypes to protect.Les changements environnementaux induits par les activités humaines impactent l'ensemble des écosystèmes marins et terrestres de la planète. Les espèces peuvent faire face à ces perturbations de différentes manières, par exemple en se déplaçant vers des habitats plus adaptés (migration et dispersion), en s'acclimatant (plasticité phénotypique) ou en s'adaptant (changements génétiques). Chez les organismes marins sédentaires comme les poissons des récifs coralliens, la principale opportunité de dispersion se situe lors de la phase larvaire, durant laquelle les larves se développent en milieu océanique avant de revenir s'installer dans les habitats récifaux. Cette dispersion larvaire dépend de facteurs physiques, tels que les courants océaniques, mais est également largement déterminée par les traits biologiques des larves, tels que leur physiologie, comportement et morphologie. Cependant, l'influence de l'environnement et des traits biologiques des parents sur ces traits larvaires associés à la dispersion reste moins bien étudiée. De plus, les jeunes poissons peuvent aussi être affectés par les stress environnementaux après s'être installés dans les récifs, soulignant l'importance de mieux comprendre leur capacité à s'acclimater à ces stress. Pour répondre à ces problématiques, ma thèse utilise le poisson clown à nageoires orange Amphiprion chrysopterus comme espèce modèle, et combine analyses in situ et en laboratoire. En collectant des œufs d'A. chrysopterus dans l'environnement puis en élevant les larves qui en découlent, j'ai d'abord étudié l'influence de la taille maternelle sur les traits larvaires associés à la dispersion (vitesse de nage et taille). J'ai pu observer que les mères les plus grandes produisent des larves qui nagent plus vite (Chapitre 2). J'ai ensuite examiné comment les conditions environnementales liées au milieu parental, telles que la taille des anémone (proxy de la qualité et de la dégradation l'habitat parental), affectent le phénotype des jeunes poissons. J'ai ainsi constaté que les parents vivant dans des habitats plus grands produisent des œufs plus grands (Chapitre 3). De plus, j'ai exploré les effets transgénérationnels et développementaux de la courantologie sur la morphologie, la physiologie et la survie des larves et des juvéniles, et observé qu'un fort courant autour des anémones influence négativement la survie des juvéniles. Ce résultat suggère notamment que l'investissement parental peut dépendre des conditions environnementales (Chapitre 4). Dans la dernière partie de ma thèse, je me suis intéressée aux effets d'expositions chroniques à deux stress environnementaux, le blanchissement des anémones (Chapitre 5) et la présence de lumière artificielle la nuit (ALAN, Chapitre 6), sur le phénotype et la survie des juvéniles d'A. chrysopterus en milieu naturel. J'ai démontré que le blanchissement des anémones affecte la physiologie et le comportement des poissons, et que les deux stress réduisent la croissance des poissons mais pas leur survie. Bien que des compromis entre croissance et survie peuvent se mettre en place, une réduction de croissance durant ces premières phases du cycle de vie pourrait avoir des effets à plus long terme sur leur fitness. Ma thèse permet donc de mieux comprendre comment et quels sont les facteurs et stress influençant le processus de dispersion et le phénotype post-installation chez un poisson emblématique des récifs coralliens. Ces connaissances aident à mieux prédire comment les populations de poissons réagissent aux changements climatiques. De telles prévisions sont essentielles aux stratégies de conservation, et permettent de cibler les zones marines et les phénotypes des poissons les plus importants à protéger

Connectivity of rocky habitat invertebrate populations in the Gulf of Lion

Connectivity has an important role for populations persistence in fragmented areas as it enables recolonization after local disturbance and compensate low local larval retention rates in sink populations. For most marine benthic invertebrates, which exhibit a complex bentho-pelagic life cycle, connectivity arises from dispersal during the pelagic larval phase. In the seascape of the Gulf of Lion, rocky habitat is fragmented and separated by large sandy areas. Objective of this study is to quantify the potential connectivity among populations of sessile or sedentary benthic invertebrates inhabiting rocky habitat of the Gulf of Lion based on numerical simulations of larval dispersal, which integrate numerical simulations of ocean currents and larval traits affecting larval dispersal. To achieve this objective, the work is organized around three axis, forming the 3 chapters of the thesis. In the first chapter, a review based on literature has been carried out collecting data on the traits affecting larval dispersal, mainly period and duration of spawning, Pelagic Larval Duration (PLD), larval size and larval motility behavior. The review includes all species building up the biodiversity of 4 hard-bottom assemblages of the Gulf of Lion. Each assemblage is designated according to the gorgonian (Octocorallia, Alcyonacea) which dominated the assemblage in terms of biomass: Paramuricea clavata (Plexauridae), Corallium rubrum (Coralliidae), Eunicella cavolinii (Gorgoniidae) and Eunicella singularis (Gorgoniidae). Gorgonians are of particular interest as they are among the main structural species of the Mediterranean hard-bottom communities due to their three-dimensional structures that create an habitat for small epifauna and refuge for several vagile species, determining the increase of the biodiversity of hard substrates. The inventory of existing knowledge clearly evidenced a lack of information about larval traits affecting larval dispersal (information available on less than 25 % of species) especially for the motility behavior. The second chapter presents new data about experimental quantification of the free-fall speed of Eunicella singularis larvae, in order to increase the information on larval traits of a benthic species abundant in the rocky habitat of the Gulf of Lion. The free-fall speed was quantified using a particle tracking routine applied to video recordings of the passive motility behavior of Eunicella singularis larvae. In the third chapter larval dispersal simulations in the Gulf of Lion were performed with a Lagrangian larva tracking model, integrating ocean currents and some larval traits, such as spawning areas, spawning period and Pelagic Larval Duration (PLD), according to the review made in chapter 1 for benthic invertebrate inhabiting rocky habitat (larval dispersal simulations are summarized in the form of connectivity matrices). This thesis was carried out at the Laboratoire d'Ecogéochimie des Environnements Benthiques (LECOB, UMR 8222), at the Observatoire Océanologique de Banyuls sur Mer, which is a joint laboratory of the Université Pierre et Marie Curie (UPMC) and the Centre National de la Recherche Scientifique (CNRS)

Déterminants parentaux et environnementaux des traits associés à la dispersion larvaire et de la physiologie post-installation

Les changements environnementaux induits par les activités humaines impactent l'ensemble des écosystèmes marins et terrestres de la planète. Les espèces peuvent faire face à ces perturbations de différentes manières, par exemple en se déplaçant vers des habitats plus adaptés (migration et dispersion), en s'acclimatant (plasticité phénotypique) ou en s'adaptant (changements génétiques). Chez les organismes marins sédentaires comme les poissons des récifs coralliens, la principale opportunité de dispersion se situe lors de la phase larvaire, durant laquelle les larves se développent en milieu océanique avant de revenir s'installer dans les habitats récifaux. Cette dispersion larvaire dépend de facteurs physiques, tels que les courants océaniques, mais est également largement déterminée par les traits biologiques des larves, tels que leur physiologie, comportement et morphologie. Cependant, l'influence de l'environnement et des traits biologiques des parents sur ces traits larvaires associés à la dispersion reste moins bien étudiée. De plus, les jeunes poissons peuvent aussi être affectés par les stress environnementaux après s'être installés dans les récifs, soulignant l'importance de mieux comprendre leur capacité à s'acclimater à ces stress. Pour répondre à ces problématiques, ma thèse utilise le poisson clown à nageoires orange Amphiprion chrysopterus comme espèce modèle, et combine analyses in situ et en laboratoire. En collectant des œufs d'A. chrysopterus dans l'environnement puis en élevant les larves qui en découlent, j'ai d'abord étudié l'influence de la taille maternelle sur les traits larvaires associés à la dispersion (vitesse de nage et taille). J'ai pu observer que les mères les plus grandes produisent des larves qui nagent plus vite (Chapitre 2). J'ai ensuite examiné comment les conditions environnementales liées au milieu parental, telles que la taille des anémone (proxy de la qualité et de la dégradation l'habitat parental), affectent le phénotype des jeunes poissons. J'ai ainsi constaté que les parents vivant dans des habitats plus grands produisent des œufs plus grands (Chapitre 3). De plus, j'ai exploré les effets transgénérationnels et développementaux de la courantologie sur la morphologie, la physiologie et la survie des larves et des juvéniles, et observé qu'un fort courant autour des anémones influence négativement la survie des juvéniles. Ce résultat suggère notamment que l'investissement parental peut dépendre des conditions environnementales (Chapitre 4). Dans la dernière partie de ma thèse, je me suis intéressée aux effets d'expositions chroniques à deux stress environnementaux, le blanchissement des anémones (Chapitre 5) et la présence de lumière artificielle la nuit (ALAN, Chapitre 6), sur le phénotype et la survie des juvéniles d'A. chrysopterus en milieu naturel. J'ai démontré que le blanchissement des anémones affecte la physiologie et le comportement des poissons, et que les deux stress réduisent la croissance des poissons mais pas leur survie. Bien que des compromis entre croissance et survie peuvent se mettre en place, une réduction de croissance durant ces premières phases du cycle de vie pourrait avoir des effets à plus long terme sur leur fitness. Ma thèse permet donc de mieux comprendre comment et quels sont les facteurs et stress influençant le processus de dispersion et le phénotype post-installation chez un poisson emblématique des récifs coralliens. Ces connaissances aident à mieux prédire comment les populations de poissons réagissent aux changements climatiques. De telles prévisions sont essentielles aux stratégies de conservation, et permettent de cibler les zones marines et les phénotypes des poissons les plus importants à protéger.Environmental changes induced by human activities impact marine and terrestrial ecosystems worldwide. While facing these perturbations, species may respond in a variety of ways, including migration to a more suitable habitat via dispersal, acclimation via phenotypic plasticity or adaptation via genetic changes. The main opportunity for dispersal in sedentary marine organisms such as coral reef fish is the pelagic larval phase, during which larvae journey in open water before settling onto a suitable habitat. Marine larval dispersal depends on physical factors, such as ocean currents, but is also largely determined by biological larval traits, such as physiology, behaviour and morphology. However, in which way offspring traits associated to dispersal are influenced by either their local environment or their parental legacy, remains less well studied. After larval settlement, phenotypes can still be affected by environmental stressors and thus it is vital to also understand their ability to acclimate to environmental stressors induced by human activities. To answer these questions, I used the orange fin anemonefish Amphiprion chrysopterus as a model species and combined in situ and laboratory analyses. First, by using laboratory reared larvae of wild spawned eggs I explored the influence of maternal size on dispersal-associated traits throughout ontogeny (swimming performance and body size) and demonstrated that larger mothers produce larvae that swim faster (Chapter 2). Then, I investigated how anemonefish parental environmental conditions, such as anemone habitat size (proxy of habitat quality and degradation) affect offspring phenotype (i.e. egg size, larval size and larval swimming performance) and found that parents living in larger habitats produce larger eggs (Chapter 3). In addition, I explored the transgenerational and developmental effects of water flow regimes on larval and juvenile morphology, physiology and survival. Results show that early life survival can be affected by the water flow regime that their parents live in, suggesting differential investment (Chapter 4). In the last part of the thesis I focused on the direct effects of chronic exposure to environmental stressors, such as anemone bleaching (Chapter 5) and artificial light at night (ALAN, Chapter 6) on juvenile A. chrysopterus phenotypes and survival in the wild. I demonstrated that anemone bleaching affects the physiology and behaviour of fish and that both bleaching and ALAN reduce fish growth but not survival, suggesting that wild fish may trade-off growth with survival, even though reduced growth at early stages may have life-long fitness effects. The results of this PhD provide a better understanding of the origin of the variability in the factors influencing the dispersal process as well as the post-settlement phenotype in an iconic coral reef fish. This knowledge may help to better predict how fish populations will respond to climate change. Such predictions are key to mitigating the impacts of climate change and improving the conservation strategies, for example by targeting the most important marine areas and fish phenotypes to protect