On the performance of radiocarbon and quartz OSL dating in macrotidal estuarine environments: Four case studies from Western France
The study of estuarine sedimentary archives provides valuable insights into their geomorphological evolution over the past two centuries, enhancing our understanding of estuarine responses to climate change. Establishing a reliable and precise geochronological framework is therefore essential for monitoring these changes. This study evaluates the performance of quartz Single-Aliquot Regenerative (SAR) OSL and AMS 14C dating in four estuaries along the western coast of France. The results are compared with cartographic data, serving as an independent age control. Of the 14 OSL dated samples, 10 yield depositional ages consistent with cartographic data, whereas the remaining 4 appear to overestimate ages by 20–100 years. In contrast, AMS 14C dating reveals numerous stratigraphic inversions, with at least 12 out of the 16 measured samples overestimating the depositional age in some cases by up to 5000 years, in total disagreement with cartographic data. The discrepancy between the OSL and radiocarbon ages reflects the constant reworking of allochthonous material, to which is added the further uncertainty associated with the local reservoir age. These factors fundamentally limit the reliability of 14C dating regardless of the material analyzed. By contrast, the OSL signal displays remarkable resilience, with any age overestimation linked to partial bleaching remaining minor (on the order of decades) compared with the errors affecting 14C ages. This underscores the capacity of OSL dating to resolve short-term environmental changes and positions it as the most reliable tool for constructing high-resolution chronologies of the last centuries in macrotidal estuarine settings.
(Quaternary Geochronology. vol. 92, n° 1871-1014, pp. 101723, 01/02/2026)
M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, DTU, UCPH, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, Nantes Univ, Cerema, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Exploring the environmental distribution of the oyster parasite Haplosporidium costale
The protozoan parasite Haplosporidium costale is known to occur in the USA where it has been associated with sharp seasonal mortality of the Eastern oyster Crassostrea virginica since the 1960’s. In 2019, the parasite was detected for the first time in the Pacific oyster Magallana gigas in France in the context of light mortality and was subsequently detected in archived material collected since 2008. This detection raised several questions regarding the ability of the parasite to maintain in the ecosystem and the potential involvement of other species in its life cycle. To answer these questions, an integrated sampling approach was deployed seasonally in three oyster farming areas where the parasite was already known to occur. Parasite presence was evaluated after checking the presence of PCR inhibitors and using a previously developed and validated Real Time PCR assay, optimized in this study to detect parasite DNA in various environmental compartments. Parasite DNA was almost only detected in cupped oysters. Considering the high number of oysters found positive with low infection intensity, a complementary experiment was undertaken to better characterize sub-clinical infections in oysters. The presence of the parasite was tested twice a week in water and sediment from aquaria hosting cupped oysters from a known infected site. After one month, oysters were sacrificed and tested regarding the presence of the parasite at the tissular level. Altogether, field and experimental results indicate that the parasite is stably established in oyster, particularly in gills, which may act as a reservoir all along the year. The detection of parasite DNA in nanoplankton and sediment suggests that H. costale is released from the oysters outside mortality event. Our results do not support the involvement of other species than cupped oyster in the parasite life cycle except periwinkles, whose role would deserve to be further investigated
(Journal of Invertebrate Pathology. vol. 214, n° 0022-2011, pp. 108462 (9p.), 01/02/2026)
ASIM, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Unraveling the Effects of Fe Incorporation on High-Performance Water-Splitting Photoanodes
Although it is known that iron (Fe) significantly alters the electrocatalytic activity of nickel (Ni)-based materials, little attention has been paid to the effects of Fe impurities on the photoelectrochemical (PEC) properties of solar-driven watersplitting photoanodes. Herein, we elucidate the crucial role of Fe in model metal-insulator-semiconductor (MIS) Si photoanodes decorated with Ni nanoparticles (NPs), known for their high performance in photoinduced water splitting. Our results demonstrate that residual Fe strongly influences the photoanodes' junction energetics and photovoltaic properties. We show that the synergistic effects (electrocatalytic/photovoltaic) caused by Fe doping explain the high performance previously reported for these model photoanodes. Crucially, Fe incorporation into the outer shell of Ni NPs and the electrolyte is essential to achieve the reported photovoltage up to 500 mV. Our investigations emphasize the importance of Fe in PEC devices, which has always been neglected in the past.
(Journal of the American Chemical Society. vol. 148, n° 0002-7863, pp. 5508-5519, 27/01/2026)
ISM, UB, INC-CNRS, CNRS, VISTEC, C2N, CNRS, LC, ENS de Lyon, UCBL, INC-CNRS, CNRS, THEO, LC, ENS de Lyon, UCBL, INC-CNRS, CNRS, CRPP, UB, INC-CNRS, CNRS, IEK-9, FZJ, IMS, UB, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A critical role of heterotrophic bacteria in early diagenesis of carbonates through exopolymer degradation and calcium release.
The degradation of exopolymeric substances (EPS) by heterotrophic bacteria, concomitant release of calcium ions and precipitation of carbonates were studied in a temperate mountain lake, Lac d'Ilay, Jura France. Phytoplankton blooms in this lake produced large amounts of exopolymeric substances (EPS; 1.8–3.0 mg L −1 ), probably inhibiting CaCO 3 precipitation by binding Ca 2+ as shown by the saturation index of calcite and aragonite remaining well below 1. EPS settled to the sediments, where additional polymeric substances were produced by the benthic community. The total amount of EPS decreased downcore from ca 50 μg/g dry sediment near the surface to ca 1.5 μg/g dry sediment at the bottom (120 cm depth). A decrease in acidity, protein and sugar content, and calcium‐binding capacity of EPS with depth coincided with active calcite precipitation. Aerobic and anaerobic EPS‐degrading heterotrophic enrichments were obtained from the top, middle and bottom of the core. Doubling times of aerobic cultures from the top were six times shorter than those of cultures obtained from the bottom of the core, but anaerobic growth rates were similar across all enrichments. Aerobic turnover rates of organic compounds decreased by a factor of 4–5 from top to bottom; anaerobic rates were similar at all depths, except for the turnover of polymers, which was negligible at the surface compared to rates at the middle and bottom. All enrichments released calcium when grown on EPS. Growth on calcium‐saturated EPS in anaerobic cultures obtained from the bottom of the core was the slowest, but still released 26% of the Ca in 20 days. This release during EPS degradation explained an increase in free calcium ions with depth reported in a previous study and may account for a large fraction of the carbonate mud. This suggests that sediments should be considered as an important source of biogenic carbonates.
(Depositional Record. vol. 12, n° 2055-4877, pp. e70057, 16/01/2026)
UCONN, BGS, EPHE, PSL, CNRS, UBE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, Unibas, UNSW, UNC, UNC
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, CSIC, LERPAC, COAST, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Past trajectory of a Northwest Europe socio-ecosystem at the land-sea interface: Case study of the northern watersheds of the Bay of Brest over the last 150 years
The Bay of Brest (BB) is a macro-tidal estuarine environment that has been exposed to strong anthropogenic pressures over the past few decades, especially since the Second World War. This makes the BB an ideal site for studying coastal ecosystem transformations since the Industrial Revolution. We analysed five sediment cores collected in two key BB areas with varying exposure to marine hydrodynamic processes: i) the Elorn sector (3 cores) and ii) the Bay of Daoulas (2 cores) in the inner BB, close to the mouth of the Daoulas river. Our study used palynological (pollen and dinoflagellate cysts) and benthic foraminiferal assemblages, sedimentological data, and elemental geochemistry, at a very fine temporal resolution (2 to 16-year resolution). Working at a local spatial scale reveals robust correlations between the different driving forces and environmental changes over the last 150 years. Statistical analyses of these sedimentological and paleoecological time series reveal major breakpoints, specifically four key threshold periods: 1925–1938, 1960–1967, 1980–1987, and 2005, which are essential for understanding temporal changes in protist communities and the evolution of BB landscapes over this time period. Combining these findings with a reanalysis of regional precipitation patterns back to 1850, nutrient concentration data, and historical accounts of land-use practices, enables us to identify the main drivers of coastal ecosystem transformation. Our findings emphasize the strong influence of agricultural practices on trophic changes and the decline in the BB water quality, in agreement with coastal observatory series showing a notable increase in toxic algal blooms since the 1980s.
(Palaeogeography, Palaeoclimatology, Palaeoecology. vol. 690, n° 0031-0182, pp. 113703, 07/04/2026)
GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS, BEEP, IFREMER, UBO EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEOARCHI, UBS, UBO EPE, IBSHS, UBO EPE, ENS Rennes, GR, UR, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, LMBA, UBS, UBO EPE, CNRS
Wave Input-Reduction for Shoreline Modelling of a High-Energy Environment with Complex Geological Settings
The long-term (decades) evolution of shoreline change along coastline (O(15)Km) with complex offshore wave transformation challenges both, state of the art process-based morphodynamics and reduce-complexity shoreline models. A major limitation is the computational time required to simulate the detailed spatiotemporal evolution of the wave field, particularly in regions where offshore wave refraction induces localized energy focusing. This study focuses on a 15-Km sandy coast on the North Medoc, southwestern France, characterized by high-energy, macro-tidal conditions, severe erosion, and complex offshore bathymetry. Effective coastal management strategies for the coming decades require the implementation of a reduced-complexity (RC) shoreline model. However, oversimplification of wave transformations in such a complex hydro-morphodynamic environment can result in flawed predictions of alongshore wavebreaking parameters and, consequently, shoreline change. Thus, a full wave propagation model is required, but computational time reduction techniques must be implemented to minimize computational cost. To address these challenges, this study introduces an easy-to-apply input reduction (IR) methodology that integrates offshore wave clustering to reduce computational costs when modeling long-term shoreline change within RC shoreline models.
(. vol. 42, pp. 652-658, 07/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM
Non-stationary Model Free Parameter in Equilibrium Shoreline Modelling
The state-of-the-art equilibrium shoreline model proposed ShoerFor [1] is used to hindcast shoreline evolution. A similar approach to the work of Ibaceta et al. (2022) [2] is adopted, where they introduced non-stationary model free parameters to improve long term shoreline change predictions. An Ensemble Kalman Filter (EnKF) is implemented to track the temporal variability in model free parameters and explore if their evolution can be linked to the environmental forcing. A correlation between the winter wave energy and the model free parameter φ (beach memory) is identified where high energetic winters are followed by an increase in the parameter suggesting such time variation in beach memory can be parametrized.
(. vol. 42, pp. 646 - 651, 07/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, UNSW