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First direct-drive implosions and produced neutrons for development of a particle source platform on the laser megajoule
No full textInternational audienceA first series of direct-drive implosions was performed on LMJ by the end of 2019, producing for the first time DD fusion neutrons and yield. This experiment, consisting of two laser shots on glass (SiO2) gas-filled spherical capsules, was aimed at commissioning the time-of-flight neutron diagnostic. The experimental results are presented in detail and compared to 3D calculations. A non-dedicated beam geometry was employed due to the limited number of laser beams available at this time, creating very strong irradiation asymmetries. An exploding pusher implosion regime was chosen to guarantee a sufficient number of neutrons. Yields of approximately 51010 were achieved, allowing the diagnostic commissioning. Discrepancies between experimental results and 3D calculations are observed and probably originate from strong distortions of the shell during the implosion, limiting the experimental yield compared to the simulated one
Vers un suivi de l'état écologique des mangroves françaises inspiré du RNQS : identification de bioindicateurs microbiens benthiques
No full textInternational audienceDans le contexte de la Directive Cadre sur l’Eau (DCE), une meilleure compréhension des communautés microbiennes benthiques des mangroves françaises est essentielle pour développer des indicateurs écologiques robustes. Les sédiments des mangroves abritent une biodiversité microbienne exceptionnelle, avec des bactéries et archéesassurant des fonctions essentielles telles que la minéralisation de la matière organique et le recyclage des nutriments indispensables aux palétuviers. Pourtant, ce compartiment reste peu étudié dans les territoires ultramarins français. Le projet DCE Mangroves vise à combler cette lacune grâce à la caractérisation de la diversité microbienne benthique étudiée en Guyane, Martinique, Guadeloupe et Mayotte. L’approche repose sur trois niveaux d’analyse moléculaire : (1) la quantification de la biomasse microbienne totale (ADN total), (2) l’évaluation quantitative des bactéries et archées (qPCR 16S rRNA), et (3) la caractérisation approfondie de la diversité et de la structure des communautés bactériennes et archéennes par Metabarcoding 16S rRNA. Les premiers résultats (campagnes de 2017 à 2019) révèlent que ces paramètres microbiens varient selon des conditions naturelles (granulométrie, pH) et anthropiques (contaminants spécifiques aux sites étudiés). Ces travaux ont notamment permis d’identifier certaines familles bactériennes sensibles à lacontamination anthropique comme bioindicateurs prometteurs (Fiard et al., 2022, 2024). Un enjeu majeur demeure cependant la compréhension de la variabilité spatiale et temporelle de ces communautés pour garantir la pertinence opérationnelle et la transférabilité de ces bioindicateurs vers d’autres écosystèmes côtiers. Ce travail est en cours avec des résultats complémentaires attendus d’ici 2027
Using Long‐Term Ecological Datasets to Unravel the Impacts of Short‐Term Meteorological Disturbances on Phytoplankton Communities
No full textInternational audienceExtreme meteorological events such as storms are increasing in frequency and intensity, but our knowledge of their impacts on aquatic ecosystems and emergent system properties is limited. Understanding the ecological impacts of storms on the dynamics of primary producers remains a challenge that needs to be addressed to assess the vulnerability of freshwater ecosystems to extreme weather conditions and climate change. One promising approach to gain insights into storm impacts on phytoplankton community dynamics is to analyse long‐term monitoring datasets. However, such an approach requires disentangling the impacts of short‐term meteorological disturbances from the effects of the seasonal trajectories of meteorological conditions. To this end, we applied boosted regression tree models to phytoplankton time series from eight relatively large lakes on four continents, coupled with a procedure adapted to detect and quantify rare events. Overall, the patterns and potential drivers we identified provide important insights into the responses of lakes to short‐term meteorological events and highlight differences in the response of phytoplankton communities according to lake morphological characteristics. Our results indicated that deepened thermoclines and lake‐specific combinations of drivers describing altered thermal structures caused deviations from the typical trajectories of seasonal phytoplankton succession. For shallow polymictic lakes, shifts in phytoplankton succession also depended on changes in light availability. Overall, our study highlights the value of long‐term monitoring to improve our understanding of phytoplankton sensitivity to short‐term meteorological disturbances
Addressing spatial confounding in geostatistical regression models: An R‐ INLA approach
No full textInternational audienceAbstract Spatial confounding, which has been studied extensively in recent years, can explain inconsistencies between results obtained by regression models with and without spatial modelling. While the most common solutions for spatial confounding mitigation often target areal data or geostatistical data modelling by splines, we aim to extend some resolution methods for geostatistical data modelling by Gaussian Markov Random Fields (GMRF) using R‐INLA methodology, aided by the R‐inlabru package. We focus on four sought‐after approaches for alleviating spatial confounding: Restricted spatial regression (RSR), geoadditive structural equation model (gSEM), Spatial+, and its simplified version, called here Spatial+2.0. We show how each can be implemented from geostatistical data in a GMRF framework using R‐inlabru. Next, a simulation study that produces a spatial confounding phenomenon in a geostatistical context is carried out to assess the coherence of the proposed extensions with the expectations of these methods. Then we apply the expanded approaches to a case study, linking cadmium (Cd) concentration in terrestrial mosses to Cd concentration in air. Our findings support the feasibility of our extended approach of spatial confounding resolution methods to geostatistical data using R‐inlabru in keeping with the previous contexts, although certain precautions and limitations must be considered
Observation des poissons côtiers rocheux d'Atlantique Nord Est par metabarcoding sur ADN environnemental et comptages visuels en plongée : Projet Viz-eDNA
No full textDans le cadre de la DCSMM, PatriNat soutient le développement d’une stratégie nationale de surveillance des peuplements de poissons récifaux, associés aux substrats durs côtiers et circalittoraux. Ces communautés, essentielles au fonctionnement des écosystèmes et à la biodiversité, sont soumises à de multiples pressions anthropiques, aggravées par le changement global.Le projet Viz-eDNA, porté par le MNHN en collaboration avec BOREA et PatriNat, combine deux méthodes non invasives et complémentaires : les comptages visuels en plongée (UVC) et le metabarcoding sur ADN environnemental (ADNe). L’objectif est d’améliorer les connaissances sur la distribution des poissons récifaux, de caractériser l’influence des forçages naturels et anthropiques et de développer des métriques utiles à l’évaluation du bon état écologique.Les résultats, malgré les biais liés à l’hétérogénéité de l’effort d’échantillonnage, révèlent un gradient latitudinal marqué des assemblages, avec une richesse plus élevée dans le Golfe de Gascogne Sud et des communautés moins diversifiées dans les régions nordiques. Le metabarcoding permet une détection élargie, incluant des espèces rarement observées en UVC, tandis que les UVC apportent une résolution spatiale fine et des estimations d’abondance et de biomasse.La complémentarité de ces deux approches démontre leur pertinence pour le suivi à long terme des peuplements de poissons récifaux tempérés. Les premières analyses au sein de l’UMR Mer Celtique et Manche Ouest ont permis d’identifier un ensemble de métriques sensibles aux variations environnementales, ouvrant la voie au développement futur d’indicateurs opérationnels pour l’évaluation du bon état écologique. Néanmoins, ces analyses doivent être étendues aux autres UMR afin de valider ces avancées. De plus, la définition de seuils de référence permettant de définir le bon état écologique demeure limitée par le manque de données sur certaines pressions anthropiques et par l’absence de mesures de gestion ciblées et spatialisées, les sites étudiés semblant tous être dans un état écologique relativement similaire. Des travaux complémentaires, notamment de transfert deconnaissances de zones géographiquement proches, bien suivies et pourvues d’AMP strictement protégées, pourraient permettre de pallier au manque de données actuellement à disposition en développant des approches basées sur la fonctionnalité des peuplements plutôt que leur composition spécifique, vouée à changer d’une région à l’autre
Modelling endurance in free-ranging animals using tracking collars: insights from domestic hunting dogs
No full textInternational audienceEndurance is crucial for animal survival yet remains poorly studied in free-ranging animals. An animal's endurance time decreases as a hyperbolic function of increasing exercise intensity, called the speed–duration relationship. This relationship allows for defining critical speed, the endurance threshold separating efforts where metabolic homeostasis is achievable from efforts where fatigue accumulates drastically. Using tracking collars on domestic dogs during hunting sessions, we demonstrated the ability to determine the speed–duration relationship and its parameters: the initial speed (Si), critical speed (Sc) and distance reserve (DAC,max). This new method exhibits good repeatability across sessions and bypasses conventional laboratory assessment, allowing the characterisation of physical capacities in natura. Our approach provides the unique possibility to study when, where and how long free-ranging animals experience fatigue and helps uncover how environmental factors affect their energy expenditure
It's time to go—Drivers and plasticity of migration phenology in a short‐distance migratory ungulate
No full textInternational audienceRecurring events like migrations are an important part of the biological cycles of species. Understanding the factors influencing the timing of such events is crucial for determining how species face the pervasive consequences of climate change in highly seasonal environments. Relying on data from 406 GPS‐collared Alpine ibex Capra ibex monitored across 17 populations, we investigated the environmental and individual drivers of short‐distance migrations in this mountain ungulate. We found that vegetation phenology, including spring growth and autumn senescence, along with snow dynamics—snowmelt in spring, onset of snow cover in autumn—were the main drivers of the timing of migration. In spring, ibex migration timing was synchronized with the peak of vegetation green‐up, but more in males than in females. Specifically, a peak of green‐up occurring 10 days later delayed migration by 6.4 days for males and 2.7 days for females. This led to increased differences in migration timing between sexes when the peak of green‐up occurred early or late in the season. In addition, ibex delayed migration timing when the length of the spring season was longer and when the date of snowmelt on ibex summer ranges occurred later. Similarly, in autumn, prolonged vegetation senescence and delayed onset of snow cover led to later migration. Overall, we observed a high degree of behavioural plasticity, with individuals responding to inter‐annual variations in vegetation and snow phenology, even though the extent of these adjustments in migration dates was lower than the magnitude of the interannual changes in environmental conditions. Nonetheless, females could be less plastic than males in their timing of spring migration, likely due to the parturition period following migration forcing them to trade off foraging needs with predation risk. As the identified drivers of ibex migration are known to be and will continue to be largely impacted by climate change, the capacity of ibex to respond to such rapid changes could differ between sexes
A novel framework for phytoplankton biomonitoring: Trait assignment of 23S rRNA sequences
No full textInternational audiencePhytoplankton is a key biological group used to assess the ecological status of lakes in several legislative water management plans. Two cutting-edge approaches for community characterization are DNA metabarcoding and trait-based analyses. While the former provides a fast, cost-effective and high-throughput methodology for identifying communities, the latter reveals the structure of communities through bio-ecological traits. The main aim of this study was to combine these approaches to directly assign traits to amplicon sequence variants. To achieve this, we used the newly developed Phytool v3 reference database. Using an in silico test, we assessed the efficiency and reliability of our approach. We found: (1) that a greater number of sequences with better reliability can be assigned to traits than to genus or species level and (2) that traits are conserved in the phylogeny with varying extent. Then, we tested the usefulness of direct trait assignment on environmental samples from lakes. The test showed a greater number of successfully assigned sequences and a good ecological interpretation of community structures in the different environments. Furthermore, we identified three factors (completeness of the reference library, sequence similarity and the number of neighbours in the reference database) which, depending on the trait under consideration, interfere with the assignment success of our approach. While DNA metabarcoding data can be exploited in many ways depending on the objectives, our study showed that an innovative framework based on direct trait assignment of sequences could overcome gaps in reference databases and further improve our knowledge of phytoplankton community structure
Experimental Evidence for the Desynchronization of Ecosystem Dynamics by Global Change
No full textInternational audienceAnticipating ecosystem responses to global change requires identifying the isolated and combined effects of environmental disturbance across both space and time. Examining the coordinated responses of ecosystems has recently emerged as a powerful approach to advance this understanding. We conducted two complementary experiments to identify whether, and if so how, warming temperatures, nutrient enrichment, predator overexploitation (i.e., reduced apex predator abundance) and their combination drive coordinated responses of freshwater ecosystems by evaluating the dynamics of synchrony between control and disturbed mesocosms using high‐frequency dissolved oxygen saturation measurements, an integrative parameter of the metabolic balance of ecosystems. Nutrient enrichment desynchronized the oxygen dynamics and their component cycles between treatments, likely arising from elevated primary production. Warming and overexploitation tended to desynchronize oxygen cycles from the control, particularly at short time scales. Nutrient enrichment combined with warming dampened desynchronization between control (ambient) and treatment mesocosms, whereas desynchronization was enhanced when simultaneously subject to predator overexploitation. As one of the first experimental demonstrations of global change impacts on ecosystem synchrony, this study highlights the need—and opens new avenues—to detect alterations in ecosystem functioning across previously unexplored spatial and temporal scales
Inégalités de genre dans le baguage d'oiseaux : causes, effets et leviers
No full textIl s'agit d'un rapport technique de recherche produit au sein du CESCO/CRBPO, contenant des analyses statistiques originales (modèles de régression, données quantitatives sur 570 participants) que le laboratoire souhaite diffuser pour la communauté scientifique (Ornithologie/Sociologie).An analysis conducted in 2025 on the bird banding community highlighted the low representation of women among qualified volunteers, despite parity observed during training. While women make up approximately half of the banding assistants, they constitute only 5% of the banders. This study examines the mechanisms that produce this gender disparity and seeks to move beyond the explanation based solely on individual choice. Indeed, the origins of this historically male-dominated social world and the codes it upholds—such as a strong competitive spirit—are regularly cited as the main factors deterring women from banding. However, the survey allows us to qualify this interpretation and to highlight a number of obstacles that prevent women from achieving qualification. An accumulation of structural constraints leads to the (self-)exclusion of women from the banding process. Several factors are identified based on the reflections of Dulong (2021), stemming from sociological (gendered socialization), anthropological (bias and stereotypes about "the feminine"), and organizational (unintentionally discriminatory rules) dimensions.The study highlights various factors of (self-)exclusion that demonstrate how external and internal obstacles within the bird banding community are constructed and mutually reinforced. Outside the banding community, there is the mental load in private life; this burden falls disproportionately on women, reducing their opportunities to participate in banding training. Furthermore, this training already represents a greater time investment for women, who generally start with less ornithological knowledge than men. A second important factor is gendered socialization, which tends to exacerbate feelings of illegitimacy among women—a handicap in a training program that values initiative. Furthermore, confidence is a major asset in reaching the qualification exam: there is no difference in skill level between men and women, who pass the exam in the same proportions; however, fewer women take the exam. In addition to the factors mentioned above, an internal problem within the bird banding community hinders the smooth progress of training for women: they are more likely to face direct discrimination and verbal, and sometimes physical violence – risks exacerbated by the configuration of the banding stations. This accumulation of factors leads us to examine the social mechanisms developed by those who remain, not only in bird banding, but more broadly, in environmental professions.These multiple factors highlight the contingent nature of certain elements, particularly those related to the organization of bird banding, which can be mitigated by institutional intervention. This work opens up avenues for reflection on revising training methods, field practices, and conditions of access to qualification, in order to promote more equitable and sustainable female participation within the bird banding community. Beyond the question of gender dynamics, this research captures the signs of more general transformations occurring in bird banding, seeing a leisure activity giving way to an increasingly professional approach to the practice, a context conducive to the evolution of values, norms, and potentially more inclusive practices.Une analyse conduite en 2025 sur la communauté des bagueur.euse.s d’oiseaux a mis en évidence la faible féminisation des bénévoles qualifié.e.s, malgré une parité observée pendant la formation. Si les femmes représentent environ la moitié des aide-bagueur.euse.s, elles ne constituent plus que 5 % des bagueur.euse.s. La présente étude interroge les mécanismes qui produisent cette disparité genrée et cherche à dépasser l’explication d’une exclusion résultant du simple choix individuel. Ce sont en effet les origines de ce monde social, historiquement masculin, et les codes qui y sont revendiqués – comme un fort esprit de compétition, qui sont régulièrement pointés du doigt comme principaux facteurs du détournement des femmes de l’activité de baguage. Pourtant, l’enquête permet de nuancer cette lecture et de mettre en évidence une pluralité d’obstacles qui empêchent les effectifs féminins de parvenir jusqu’à la qualification. Une accumulation de contraintes structurelles conduit à l’(auto)-exclusion des femmes du parcours de baguage. Différents facteurs sont identifiés à partir des réflexions de Dulong (2021), relevant d’une dimension sociologique (socialisation genrée différenciée), anthropologique (biais et stéréotypes sur le « féminin ») et organisationnelle (règles involontairement discriminantes).L’enquête met en avant différents facteurs d’(auto)-exclusion qui témoignent de la manière dont des obstacles externes et internes au monde du baguage se construisent et se renforcent mutuellement. A l’extérieur de la communauté de baguage, la charge mentale dans la vie privée ; cette dernière repose en plus grande partie sur les femmes, ce qui réduit leurs opportunités de s’investir dans la formation de baguage. Cette formation représente en outre déjà un investissement de temps plus important pour les femmes, qui partent en général avec moins de connaissances en ornithologie que les hommes. Un deuxième facteur important est la socialisation genrée différenciée qui a tendance à exacerber chez les femmes le sentiment d’illégitimité – un handicap dans une formation qui valorise la prise d’initiative. L’assurance est, de surcroît, un atout majeur arriver jusqu’à l’examen de qualification : aucun écart de niveau n’existe entre hommes et femmes, qui réussissent dans les mêmes proportions cet examen ; en revanche, les femmes sont moins nombreuses à se présenter. En plus des facteurs précédents, un problème interne à la communauté de baguage représente un obstacle au bon déroulement de la formation pour les femmes : elles sont plus susceptibles de faire face à une discrimination directe et à des violences verbales, parfois physiques – des risques renforcés par la configuration des stations de baguage. Cette accumulation de facteurs amène à se pencher sur les mécanismes sociaux développés par celles qui restent, pas seulement dans le baguage, mais plus largement, dans les métiers de l’environnement.Ces pluralités de facteurs permettent de mettre en évidence le caractère conjoncturel de certains facteurs, notamment ceux relevant de l’organisation du baguage, qui peuvent être amoindris par une intervention institutionnelle. Ce travail ouvre des pistes de réflexion pour réviser les modalités de formation, de pratiques de terrain et les conditions d’accès à la qualification, afin de favoriser une participation féminine plus équitable et durable au sein de la communauté des bagueur.euse.s. Au-delà de la question des dynamiques genrées, cette recherche saisit les signes de transformations plus générales traversant le baguage ornithologique, voyant une pratique de loisir céder du terrain à une appréhension de plus en plus professionnelle de la pratique, un contexte propice à l’évolution des valeurs, des normes et des pratiques potentiellement plus inclusives