Rôle de la variabilité spatio-temporelle de la couverture végétale sur la migration des cordons dunaires en Gironde
La détection et le suivi de la variabilité spatio-temporelle de la végétation dunaire sont déterminants afin de comprendre et anticiper les évolutions morphodynamiques des cordons dunaires. En comparaison avec d'autres régions européennes plus septentrionales, où la végétation dunaire est plus dense et dont les limites spatiales sont plus facilement identifiables, la végétation dunaire en Nouvelle-Aquitaine est plus éparse et sa détection et quantification représentent un défi scientifique. Une nouvelle méthode couplant l'imagerie satellitaire (Sentinel-2, 10 x 10 m) et l'utilisation d'un réseau de neurones (S2DR3) est présentée dans cette étude. Cette méthode permet d'obtenir une cartographie d'un indicateur de végétation (NDVI) à haute résolution spatiale (1 x 1 m) et de renouveler l'opération à une fréquence annuelle. L'évaluation des erreurs de géoréférencement (< 5 m) et de la cohérence spectrale des images satellite (0.73 < R < 0.86) a démontré la fiabilité de cette méthode, permettant d'analyser les variations spatio-temporelles de la végétation. Les résultats ont montré une diminution des valeurs de NDVI, de plus de moitié entre 2017 et 2024 avec de fortes disparités spatiales le long d'une section dunaire de 500 mètres située au nord de Carcans Plage (Gironde). En associant cette cartographie de la végétation avec des données topographiques (LiDAR aéroporté), des interactions entre la dynamique de végétation et les changements morphologiques ont pu être identifiées en mettant en évidence différents niveaux de couverture de végétation et de mobilité sédimentaire. Ces données offrent également de nouvelles perspectives, comme notamment leur intégration dans des modèles numériques morphodynamiques afin d'avoir une compréhension plus fine des interactions entre la végétation et la dynamique sédimentaire
(23/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM
First and disturbing records of the bivalve molluscs Potamocorbula amurensis (Schrenck, 1861) and Mulinia lateralis (Say, 1822) in the Bay of Biscay (France)
The bivalve mollusc Potamocorbula amurensis, a Corbulidae from the Asian coasts, was recorded for the first time in France in September 2023 in the Gironde estuary, and subsequently in September 2024 in Aiguillon Cove and Aytré Bay. In Aytré Bay, it was accompanied by another non-native bivalve not previously reported from French coasts, Mulinia lateralis, a Mactridae from the western Atlantic coasts. These two species were first recorded in Europe in 2018 in the Westerschelde (Netherlands, Belgium) and are known to be potentially highly invasive. Particular attention should be paid to monitor the spread and the establishment of these two euryoecious species along European coasts.
(An Aod - Les cahiers naturalistes de l’Observatoire marin, n° 2263-5718, 23/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, OBIONE, LIENSs, INSU - CNRS, ULR, CNRS, LPO, PatriNat, MNHN, IRD, CNRS, OFB - DSUED, OFB, PatriNat, MNHN, CNRS, OFB, PatriNat, MNHN, CNRS, AFB
Molecular detection reveals infection phenology of a host – Trematode system (Cerastoderma edule – Bucephalus minimus) in southwestern France
Accurate detection of parasites in their hosts is essential for pathogen control and ecosystem studies. The trematode Bucephalus minimus (Digenea: Bucephalidae) infects the edible cockle Cerastoderma edule, a commercially fished and ecologically important bivalve that serves as its first intermediate host, in which it can be difficult to detect. We investigated detection accuracy and infection phenology of this host-parasite system in Arcachon Bay, France. Cockles were collected monthly over one year to compare detection methods: stereomicroscopy of tissues versus molecular detection by quantitative PCR (qPCR) and digital PCR (dPCR). Visual detection reported 30% prevalence, qPCR 36%, and dPCR 50%, the most sensitive method. Seasonal cockle sampling and cohort analysis enabled tracking of the 2021 cohort over two years (Sep 2022 -Jun 2024) using both visual and molecular detection. With both approaches, first infection appeared when the cohort reached 14 mm shell length in fall 2022, most likely coinciding with sexual maturity. Molecular detection consistently revealed higher prevalence and greater temporal variation than visual detection, allowing for the first description of an infection phenology in this system. Prevalence sharply rose in spring 2023, was highest in summer, declined in fall, and increased again in spring 2024 to a lesser extent. These fluctuations appear linked to cockle size and maturity, as well as to the migration pattern of the definitive host (Dicentrarchus labrax), both influencing parasite transmission. Our results highlight the importance of using sensitive molecular methods to accurately assess parasite prevalence and understand transmission dynamics, essential for monitoring parasite and host populations.
(Journal of Invertebrate Pathology. vol. 216, n° 0022-2011, 23/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMS POREA, INSU - CNRS, CNRS, INRAE, ECOMAP, AD2M, SU, CNRS, SBR, SU, CNRS
Organic carbon composition and preservation in macrotidal coastal wetland sediment: insights from biomarkers and isotopic signatures
Coastal wetlands store high amounts of organic carbon (OC) in their sediments, but long-term preservation of this carbon depends on habitat type, sediment depth, and the molecular characteristics of organic matter (OM). This study explores the dynamics of OC deposition and preservation across vertical profiles (0–30 cm) in two adjacent coastal habitats—mudflat, and salt-marsh—within the macrotidal system of the Aiguillon Bay (France). A multi-tracer approach was applied, combining stable isotopes δ13C, C/N ratios, lignin phenols, and fatty acids. Sediment OC content ranged from 13.4 to 23.2 mgC g−1, with the highest concentrations found in the salt-marsh. δ13C and C/N signatures revealed dominant marine source in the mudflat, with a secondary contribution from microphytobenthos, and mixed marine–C₃ plant inputs in the salt-marsh. Fatty acids and lignin compositions supported this partitioning, with surface mudflat layers enriched in labile microbial and algal-derived compounds, whereas deeper salt-marsh sediments retained more resistant, C3 plant-derived signatures resembling those of terrestrial OM source. OM degradation rates were closely linked to source composition and depth. Degradation was concentrated within the top 5 cm of salt-marsh and the top 10 cm of mudflat. Below these depths, biomarker profiles changed minimally, delineating a transition to longer-term preservation. First-order degradation constants were three times higher in mudflat (0.53 yr−1) than in salt-marsh (0.17 yr−1), despite similarly high sedimentation rates (1.8 and 2.2 cm yr−1, respectively). This reflects differences in OM lability, with even minor contributions from microphytobenthos enhancing reactivity in mudflats. Salt-marshes, with their intermediate OM reactivity and high sedimentation rates, emerged as hotspots of carbon accumulation (366 gC m−2 yr −1), while mudflats also contributed substantially to coastal carbon sequestration (239 gC m−2 yr −1). These results highlight the value of depth-resolved, biomarker-based approaches to identify habitat-specific degradation dynamics; ultimately better understanding carbon accumulation in coastal ecosystems.
(Science of the Total Environment. vol. 1020, n° 0048-9697, pp. 181542, 23/05/2026)
LIENSs, INSU - CNRS, ULR, CNRS, iEES Paris, IRD, SU, UPEC UP12, CNRS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPG-ANGERS, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST
Late Holocene glacier fluctuations in the Northern Greater Caucasus (Russia) inferred from 10 Be cosmic ray exposure moraine dating
Our understanding of mountain glacier changes located in the Greater Caucasus during the Holocene is only loosely constrained. So far moraines were tentatively dated from sporadic cosmic ray exposure (CRE) ages, tree rings and radiocarbon ages. Here, we present 78 10 Be CRE ages that were obtained from samples collected on moraine boulders and roches moutonnees from one debris-free Terskol glacier and two debris-covered Bashkara and Donguz-Orun glaciers, all located in the Elbrus area. 10 Be CRE ages span from the beginning of the Late Holocene to the Little Ice Age. We did not found evidence of moraine formed neither during the Early Holocene nor during the Mid-Holocene suggesting that during both periods glaciers had a smaller size than during the Late Holocene, when several moraines were deposited at the base of the three glaciers. The oldest moraine that documents the largest Holocene glacier advance occurred around 3.4 ka at the base of the debris-covered Bashkara and Donguz-Orun glaciers, respectively. The debris-free Terskol glacier experienced its largest Holocene extent a bit later in the Late Holocene with moraines dated to ~2.7 ka. Subsequently several glacier advances of smaller extent were recorded almost synchronously between the three glaciers around ~2.2 ka, 1.5 ka, and during the Little Ice Age. Regional climate conditions estimated from TraCE simulations and rare proxy records suggest that the Early and Mid-Holocene were dry and warm with progressive wetter and cooler conditions during the Late Holocene concomitant with glacier evolution observed in the three valleys.
(The Holocene, n° 0959-6836, 26/12/2025)
CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE, RAS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GR, UR, INSU - CNRS, CNRS, LGP, UP1, UPEC UP12, CNRS
Investigating the potential of time‐varying free parameters in equilibrium shoreline change models through data assimilation
Equilibrium shoreline change models with calibrated, time‐invariant free parameters have demonstrated good skill in hindcasting shoreline evolution at sites dominated by cross‐shore sediment transport. However, their performance can be biased by the specific conditions present during the calibration period. In this study, a dual parameter‐state ensemble Kalman filter (EnKF) was applied to track non‐stationarity in model free parameters at three sites along the west coast of Europe. Introducing time‐varying parameters did not substantially improve performance relative to an already well‐calibrated stationary model. Model skill improvement occurred mainly during the EnKF correction step, highlighting the potential of real‐time data assimilation for maintaining model stability. Although variations in model parameters may compensate for unresolved processes and should be interpreted cautiously, incorporating climate‐driven, time‐varying parameters could improve extreme‐event predictions at seasonally dominated sites and enhance overall model performance in regions influenced by complex, multimodal wave climates.
(Earth Surface Processes and Landforms. vol. 50, n° 0197-9337, 21/12/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, UNSW, GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS
PFAS Data Hub: An open data portal featuring geovisualisation
Per-and polyluoroalkylated substances (PFAS) are a group of man-made chemical substances used in everyday products and industry processes since the 1950s. They contain carbon-fluorine bonds, among the strongest in chemistry, resulting in intrinsic or indirect extreme environmental persistence and earning them the nickname "forever chemicals". In a context of growing awareness of PFAS toxicity and widespread pollution, the Forever Pollution Project (FPP), a cross-border journalistic investigation, compiled data on measured and estimated PFAS contamination across Europe, published as an interactive map. In this data paper we present the PFAS Data Hub (PDH), a project building upon the FPP dataset and reprocessing it using a more robust and transparent methodology. We incorporated several additional data sources, most of which are automatically updated on a monthly basis. To our knowledge, this constitutes the only compilation of PFAS contamination data at the European scale. It is intended to support research projects across a wide range of different disciplines, and to be used as a source of information by journalists, citizens and civil society organisations. The data, as well as a geovisualisation tool with filtering and export options, is available on the PDH website: https://pdh.cnrs.fr.
(18/12/2025)
LIS, AMU, UTLN, CNRS, PRODIG (UMR_8586 / UMR_D_215 / UM_115), UP1, IRD, SU, CNRS, UPCité, IRISSO, PSL, CNRS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Times of changes, the latest Pleistocene micromammal association of the Salto de Piedra site (Buenos Aires Province, Argentina)
The results of the taxonomic, taphonomic, and paleoecological analyses of Late Pleistocene micromammals from the Salto de Piedra paleontological locality are presented in this paper. Our results support the conclusion that the microfaunal remains were mainly accumulated by diurnal raptors in areas close to where the remains were deposited, as there is no evidence of transport. Taxonomically, the recovered micromammals include rodents currently inhabiting the Humid Pampa (Calomys cf. C. musculinus-laucha, Ctenomys sp., and Reithrodon auritus) and species that became extinct during the Late Pleistocene (Microcavia cf. M. robusta) and Holocene (Galea tixiensis). Additionally, remains of the Patagonian marsupial Lestodelphys halli and the amphibious sigmodontine Holochilus brasiliensis were identified. These analyses, along with the paleoecological and malacological studies at Salto de Piedra, confirm a trend toward increased humidity, consistent with the paleoenvironmental evidence documented for the region at the end of the Pleistocene. This study of the central Humid Pampa based on this small mammal record is of particular interest for interpreting the paleoenvironmental and paleoecological scenario, coinciding with the arrival of the first humans in the area and the extinction of the megafauna.
(Quaternary Research. vol. 131, n° 0033-5894, pp. 116 - 133, 18/12/2025)
UV, UC3M, MNCN, CSIC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Satellite-derived shoreline data assimilation for sandy coast evolution
Understanding and predicting the evolution of sandy shorelines remains a central challenge in coastal science and a critical requirement for sustainable management. Reliable predictions require consistent observations and models capable of representing complex, non-stationary morphodynamic behaviour. This thesis advances shoreline change modelling by integrating publicly available datasets—primarily satellite-derived shoreline (SDS) observations—within calibration and data assimilation frameworks, assessing their added value. By relying exclusively on freely accessible data, the work establishes a transparent, transferable modelling foundation applicable even in data-limited coastal environments. The initial focus is on 1D equilibrium shoreline models, addressing calibration using uncorrected, noisy SDS data without tidal adjustments or a priori site knowledge. Using a simulated annealing algorithm, robust model calibrations were achieved at Truc Vert beach, a fully exposed, wave-dominated site with high-energy waves, large tides, complex intertidal bathymetry, and mild nearshore slopes that introduce substantial observational uncertainty. The strong model performance under these challenging and conservative conditions demonstrates that valuable information can be extracted from low-quality SDS, supporting broader applicability where simple equilibrium models are suitable. Applying uncorrected SDS in sequential data assimilation proved more challenging due to observation noise limiting the algorithm’s ability to track system non-stationarity. To explore the potential of time-varying model free parameters, in situ observations were used to assess links to wave climate and influence on predictive skill. Across multiple sites along the European Atlantic coast, the connection between parameter variability and climate was weak or absent, suggesting non-stationarity primarily reflects local morphodynamic adjustments. Non-stationary models showed slightly improved performance at some sites and reduced skill at others, with data quality influencing outcomes—sites with higher-quality observations benefited more. Notably, nonstationary models captured extremes of erosion, demonstrating their potential for representing rare but significant events, though stronger gains would require regions with multimodal wave climates. Building on these insights, calibration and data assimilation were combined in an international benchmark experiment at a site in Australia documented with SDS data and historical aerial photographs. Two distinct equilibrium-based models were explicitly coupled within a hybrid framework, illustrating how calibration and assimilation can complement each other. This approach highlights the potential of ad hoc hybrid modelling strategies that merge separate empirical formulations to capture multi-scale shoreline dynamics within reduced-complexity frameworks. Finally, the framework was extended to a quasi-2D configuration using grid-based data assimilation with spatial nudging. Applied to the highly dynamic Sacalin spit in the southern Danube delta, where dominant processes are not explicitly represented in the model, the approach successfully constrained shoreline evolution across the grid and improved agreement with long-term satellite observations. Although neighbouring grid dependencies were not yet considered, this implementation represents a critical step toward fully 2D assimilation capable of resolving spatial feedbacks in shoreline evolution. Overall, this work demonstrates that combining long-term satellite observations with hybrid modelling and data assimilation provides a powerful pathway for advancing understanding, prediction, and eventually operational forecasting of shoreline change in complex coastal systems.
(08/12/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Marine parasite diversity : study of cockle-trematode systems and their phenology using an environmental DNA-type approach
Digenean trematodes are among the most important groups of macroparasites in marine environments and play an important role in ecosystem functioning. Understanding their ecology requires accurate species identification and detection. However, conventional methods based on morphology have limitations, particularly for differentiating morphologically similar or cryptic species, identifying undescribed parasite stages and detecting early-stage or low intensity infections of hosts. As a result, life cycles and infection phenology often remain unresolved. Molecular approaches have the potential to overcome these barriers and help fill these ecological knowledge gaps. This thesis investigated how molecular tools can complement or surpass morphological identification in the diverse trematode community infecting the edible cockle (Cerastoderma edule), a key bivalve species of ecological and economic importance in European intertidal ecosystems, such as Arcachon Bay (France). Field surveys, laboratory experiments as well as morphological and molecular analyses were undertaken to (1) determine the reliability of morphological identification through comparison with molecular phylogenetic analyses of trematodes infecting cockles across Europe; (2) apply a targeted environmental DNA (eDNA) approach to elucidate the life cycle of the himasthlid Curtuteria arguinae by identifying its unknown hosts and assess the environmental drivers of its transmission to cockles; (3) improve detection of Bucephalus minimus sporocyst infections, a highly pathogenic bucephalid trematode, using species-specific molecular assays in order to describe its infection phenology. The European survey revealed 13 trematode species in cockles by morphology, but phylogenetic analyses uncovered 17 distinct genetic lineages. While some species were correctly identified morphologically, many were prone to misidentification or showed unexpected, potentially cryptic diversity, especially within the Himasthlidae family. This work clarified the strengths and limitations of current morphological methods of species identification and revealed that unknown infections might be more common than expected. The DNA dataset generated here also provided a solid foundation for the design of species-specific molecular tools. Building on this, a targeted qPCR-based eDNA approach allowed detection of C. arguinae DNA in water and fecal samples. The needle snail (Bittium reticulatum) and the oystercatcher (Haematopus ostralegus) were thereby identified respectively as the first intermediate host and as the definitive host, elucidating the life cycle for the first time. Experiments showed cercarial emergence was strongly temperature-dependent, driving seasonal transmission to cockles in the field. These results explain the parasite’s southern distribution and suggest potential northward expansion under climate change. Finally, molecular detection of B. minimus in cockles by species-specific qPCR and dPCR assays revealed substantially higher prevalence than microscopy, allowing the first description of infection phenology in Arcachon Bay. Infection dynamics were linked to cockle size and life history, as well as seasonal migration of the definitive host, the European seabass (Dicentrarchus labrax). Altogether, this thesis demonstrates the value of molecular methods for trematode identification and detection. These case studies show how molecular approaches, such as targeted eDNA approaches, can help resolve life cycles, detect inconspicuous infections and improve understanding of parasite phenology. Beyond the cockle-trematode systems studied here, this work highlights the broader value of molecular tools for assessing parasite prevalence, distribution and transmission and better integrating trematodes in our understanding of marine ecosystem functioning.
(05/12/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS