From Fixed to Transgressive Dunes, the Conditions and Timing of the Transition Along the Aquitaine Coast, France
Today most of the coastal dunes in temperate latitudes, especially in the northern hemisphere, are relatively stable. However, over the last decade, the Gironde coast, southwest France, has experienced substantial natural dune remobilization following a major marine erosion event. Annual, large-scale and high-resolution, airborne LiDAR data and Satellite imagery (Sentinel-2) are combined to address the coastal dune morphological changes and establish relations with forcing and controlling factors (vegetation cover, geomorphological descriptors). Between 2014 and 2023, about 10 out of 85 km of the Gironde dunes have switched from fixed to transgressive state. The analysis showed that in the vast majority of the cases the dominant process involved was dune front cannibalism. However, there is considerable spatial and temporal variability along the coast, depending on the vegetation cover evolution, the amount of sediment remobilized and the morphological characteristics of the dunes (steepness of the front slope, width)
(. vol. 41, pp. 10 - 15, 07/04/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, ONF
Influence of Estuarine Turbidity Maximum Dynamics and River Discharge on Tide Propagation in Two Fluvial-Estuarine Systems
Tidal propagation in estuaries is shaped by the balance between morphological convergence and frictional effects, yet the influence of mud deposition associated with estuarine turbidity maxima remains unexplored. This study investigates the influence of Estuarine Turbidity Maxima (ETM) dynamics and river discharge on tidal propagation in the Loire and Gironde estuaries, combining frequency analysis of high-frequency observational data with an analytical model. Enhanced Harmonic Analysis reveals a tipping section-located downstream of the saline intrusion limit-in both hyperturbid systems, beyond which tidal properties (amplification, distortion, asymmetry) become highly sensitive to river discharge. Decomposing total friction into tidal, riverine, and interaction terms shows that the tipping point marks a regime shift where tide-river interaction dominates under low flow conditions, while the river term dominates during high discharge. Observations show that seasonal and interannual ETM-induced changes in bottom roughness can modulate tidal amplification by up to 35%, a mechanism confirmed by idealized modelling, while morphological changes have a more limited effect at these scales. Finally, scenario-based simulations suggest that sealevel rise and anthropogenic deepening may further enhance tidal amplification, 1 potentially promoting the upstream migration of salinity and turbidity maxima, with broader implications for estuarine functioning under future climate and human pressures.
(Estuaries and Coasts. vol. 49, n° 1559-2723, pp. 68, 07/04/2026)
RHITME, Cerema, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOMA, UB, CNRS
Morphological Development and Evolution of Barchanoid Dunes on the Cap Ferret Coastal Spit
Barchans are crescent-shaped dunes with their convex side facing the wind and their horns pointing downwind, commonly observed in deserts but also in coastal environments. This study investigates the dune field of the Cap Ferret Spit (5-km wide, 23-km long; Atlantic Coast, SW France) including of series of barchanoids dunes, currently stabilized by forest cover. The aims are to classify each dune into distinct typologies and characterize their morphology in order to analyze their evolution. LiDAR-based analysis identified four distinct barchanoid dune types. Moreover, it revealed superimposed bedforms on the dunes, including draping and oscillating patterns, reflecting the influence of consistent wind regimes during dune development and migration. This study proposes an evolutionary sequence in which proto-barchans evolve into barchanoid ridges and eventually as mature isolated barchans. These findings provide insight into the geomorphological evolution of barchanoid dunes in a coastal context, and particularly their migration pattern on a coastal spit system
(. vol. 41, pp. 41 - 47, 07/04/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
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
(07/04/2026)
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, 07/04/2026)
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, 07/04/2026)
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, 07/04/2026)
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