Salinity Transition in the Ostia Lagoon During the Roman Period: Assessing the Feasibility of Salt Exploitation
This study examines long‐term salinity changes in the Ostia Lagoon between the 4th century cal BC and the 6th century cal AD , with emphasis on their implications for ancient salt production. Although Ostia's foundation is closely linked to the control of salt resources in the Tiber Delta, direct archaeological evidence of Roman‐period saltworks is scarce. To address this gap, this study combines micropalaeontological analysis of ostracod assemblages with a morphometric study of sieve pore features in Cyprideis torosa (Jones, 1850). This approach enables reconstruction of short‐term palaeosalinity dynamics. Core LOA–1 documents a transition from peatland to euryhaline lagoon between the 8th–6th and the 4th–3rd centuries cal BC , followed by repeated high‐salinity episodes. A notable peak coincides with the establishment of the Roman Castrum, suggesting favourable conditions for salt concentration. After the mid‐4th century cal BC , salinity peaks decreased, possibly reducing the lagoon's potential for saltworks and fostering greater reliance on the Maccarese saltworks. In the northern lagoon sector, hyperhaline conditions during the Roman period remain uncertain because of chronological gaps and the lack of sieve pore analysis. Overall, the results demonstrate both the potential and limitations of ostracod analysis as a palaeosalinity proxy and refine understanding of salt exploitation in the Tiber Delta. This study provides valuable insights into the long‐term socio‐environmental dynamics of the Mediterranean coastal wetlands, contributing to the advancement of geoarchaeological research on ancient salt production through salterns and its influence on human settlement patterns and economic practices.
(Geoarchaeology: An International Journal. vol. 41, n° 0883-6353, 10/01/2026)
Archéorient, UL2, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IGAG, CNR, CNRS, LIVE, UNISTRA, CNRS, ISCR
The role of biomolecules produced by invasive macrophytes in lake ecosystem processes
Egeria densa and Lagarosiphon major are the main invasive hydrophytes in French Atlantic Lakes. These exotic species can modify trophic levels by producing large quantities of biomass in lakes; previous investigations revealed the occurrence of endogenous metabolites in these plants known to be able to affect epiphytic communities, phytoplankton, or other plants, through allelopathic activity. Nevertheless, the actual excretion and environmental occurrence of these metabolites remain poorly documented. In order to gain knowledge of the concrete occurrence and potential ecological impact of E. densa and L. major exometabolome, untargeted metabolomics using high-resolution mass spectrometer and chemometrics approaches is relevant through its ability to depict, as a first step, the exometabolome chemical landscape.
(01/01/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EABX, INRAE
Northernmost record in the Bay of Biscay (northeastern Atlantic) of two leptothecate hydroids (Cnidaria: Hydrozoa) of southern affinity
Two leptothecate hydroids of southern affinity, Sertularella ornata Broch, 1933 and Sertularelloides cylindritheca (Allman, 1888) were collected in the southern sector of the Bay of Biscay off Saint Jean de Luz (France). The latter was also seen during several ROV surveys on rocky communities along the Cantabrian Sea and northwestern Spain. Each of the two species is herein described and illustrated and their worldwide distribution, bathymetric ranges and reproductive periods, revised; additionally, we allocate them in their biocoenological context, providing in situ images. The northern boundary limits are extended for both hydroids, which are new records for the Atlantic coast of France; the latter belongs to a genus previously unrecorded in the French mainland fauna. We also discuss the importance of having inventories of the sessile fauna of the exceptional sites at study, for the sake of their protection and detection of future modifications due to climate change.
(Journal of Marine Systems. vol. 253, n° 0924-7963, pp. 104158 (11p.), 01/01/2026)
INSUB, LERAR, COAST, IFREMER, IEO, CSIC, LERPAC, COAST, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
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, 20/02/2026)
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
Holocene climatic changes in the Kerguelen archipelago (South Indian Ocean) based on marine and lacustrine palaeoclimatic archives
Climatic variability in the Southern Hemisphere is largely controlled by the latitudinal position of the Southern Hemisphere Westerly Winds (SHW), whose migration influences precipitation, temperature, and Antarctic upwelling. This study presents the results of analyses of two lacustrine sediment cores from Lake Armor, located on the subantarctic Kerguelen Islands (49 • 15′S, 69 • 10′E), within the SHW belt. Lipid biomarkers (Glycerol Dialkyl Glycerol Tetraethers, n-alkanes, and their hydrogen isotopes) were used to reconstruct mean annual air temperature above freezing (MAF) and humidity conditions. These records are compared with a high-resolution diatom-based summer sea surface temperature (SST) reconstruction from marine core MD11-3353, situated 150 km southwest of Lake Armor. In the late glacial and Early Holocene, our results reveal a period of warm air temperature, comparable to current values and very warm sea surface temperature, 5°C above the current values. Around 9000 cal a BP, an abrupt transition occurred, marked by a cooling of 5°C in SST and 1.5°C in MAF, interpreted as a northward migration of the SHW and associated oceanic fronts. The Mid-to-Late Holocene period is characterized by pronounced MAF variability, including a notably warm interval between 3000 and 2000 cal a BP, when n-alkane dD suggests the prevalence of wetter conditions. Since ~250 cal a BP, a southward migration of the SHW has produced a 2.5°C rise in MAF. Our findings are overall consistent with previous studies from the Indian Ocean, but permit us to go a step further as by comparing SSTs and air temperatures. This suggests that SST is not a reliable predictor of air temperature on the Kerguelen Islands, particularly during the Early Holocene. We hence argue that Kerguelen air temperature is predominantly controlled by the position of westerly winds, as an indicator of reorganisations in air mass trajectories.
(Quaternary Science Reviews, n° 0277-3791, pp. 109753, 20/02/2026)
EDYTEM, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, LGL-TPE, ENS de Lyon, UCBL, INSU - CNRS, UJM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, LOCEAN-VOG, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, LOCEAN-VALCO, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, UiB, IP, INSU - CNRS, CNRS, JAMSTEC, INEE-CNRS, CNRS, INSU - CNRS
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
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