Evaluating migration hazard for recently remobilized managed coastal dunes
Sparsely vegetated or unvegetated coastal dunes are inherently dynamic, regardless of their size (Hesp et al., 2022). A salient characteristic of these dunes is their landward migration, driven by prevailing onshore winds, at rates that can exceed several meters per year. The rapid evolution of freely evolving coastal dunes inevitably raises concerns about the burial of infrastructure and more generally, the back dune areas. In a context where dune system remobilization is emerging as a nature-based management solution with multiple benefits (ecological reconnection, chronic marine erosion and sea-level rise effects mitigation), precise, spatially explicit quantitative assessments of dune migration hazards are essential. This is more critical given the trends of increasing urbanization and the concentration of socio-economic interests in coastal zones. Along the 230 km of the Aquitaine coast (southwest France), coastal dunes, which landscape is largely inherited from nearly two centuries of management, stabilization, and episodic mechanical re-profiling, have undergone spontaneous remobilization over the past decade (Nicolae Lerma et al., accepted). Across extensive sectors, dunes have transitioned from geometrically fixed, vegetated forms to aerodynamic, transgressive dunes (Figure 1a). This shift presents both opportunities and challenges for short- and long-term management strategies but also raises critical questions about accommodating rapid migration rates and evolving dune morphology. Current approaches to assessing burial hazards often overlook key parameters, such as interannual wind variability, climate change-induced trends in forcing, dune and back-dune morphology, and sediment budgets. Furthermore, methods relying on historical migration rates are inapplicable in regions where dunes were artificially stabilized during the 20th century through management interventions. Using annual airborne LiDAR data (Figure 1b.) and simulations with the morphodynamic model DUNA (Kombiadou et al., 2023, Figure 1c.), we analyze the factors influencing the migration speed of recently unvegetated dunes. We also investigate the impact of hybrid management strategies (designed to either accelerate or mitigate dune remobilization) at large spatial scales (hundreds of meters to tens of kilometers).
(13/07/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ONF
Deciphering copper and zinc leaching from antifouling paints with different operating modes: flux determination and toxicity evidence
Laboratory experiments were performed using 3 antifouling paints with different operating modes immersed in seawater for 7 days, to estimate copper and zinc fluxes and determine the scale of the related contamination. The toxicity of antifouling paints leachates was also assessed for natural bacterioplanktonic and phytoplanktonic communities. Given the increase in copper and zinc concentrations (4 to 1750-fold enrichment in dissolved Cu and to 7 to 200-fold enrichment in dissolved Zn), a systematic mortality upon phytoplankton was evidenced within 2 days of exposure to leachates produced from 1 hour to 2 days of immersion, whatever the paint. This went oppositely with the environmental risks calculated according to European guidelines, demonstrating an acceptable risk for the environment. Considering that 1 hour of leaching from a 7 cm² painted disk polluted 0.5L of seawater with Cu in our experimental conditions whatever the paint used, we estimated that a painted ship hull of 15 m² can pollute more than 10 m 3 of seawater within the same time. Leachates produced after only 20 minutes even yielded phytoplankton growth inhibition or mortality for insoluble and self-polishing paints, respectively, shortening the time needed for a freshly painted ship hull of 15 m² to pollute 10 m 3 . The bacterioplanktonic community appeared less sensitive than phytoplankton but demonstrated the same hierarchy: the highest toxicity was observed for the insoluble matrix and the lowest toxicity for the soluble one. This study therefore brings added value in terms of biocides flux determination, range of studied paints and concrete toxicity evaluation.
(Marine Pollution Bulletin. vol. 225, n° 0025-326X, pp. 119265, 01/04/2026)
MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Assessing spatiotemporal changes in the benthic habitats of the West Gironde Mud Patch through the analyses of surface sediments, benthic macrofauna and sediment profile images
This work aims to refine the current assessment of spatiotemporal changes in the benthic habitats of the West Gironde Mud Patch. It follows a survey based on the analysis of surface sediment characteristics and benthic macrofauna composition at 5 stations located along a depth gradient, which was achieved between 2010 and 2018. The present work extends this observation period to 2021 and includes the indirect assessment of bioturbation through the analysis of sediment profile image characteristics. Temporal changes in surface sediment characteristics were essentially seasonal with strong increases in chloropigment concentrations in spring. Temporal changes in benthic macrofauna composition were mostly interannual with a major difference between 2010 and 2016-2021 currently attributed to the impact of a major physical disturbance during 2013-2014. In this study, extending the observation period shows that full recovery of benthic macrofauna composition had not yet been achieved by 2021. Sediment profile image characteristics (tube and organisms numbers, area of subsurface structures, oxic void depth and aRPD thickness) showed: (i) clear seasonal changes at the two deepest stations, mostly associated with a spring increase in tube numbers; and (ii) no significant difference between 2010 and 2016-2021, except at the deepest station. The discrepancy between benthic macrofauna composition and sediment profile image characteristics may result from differences in the recovery dynamics of benthic macrofauna composition and functionalities. Overall, results clearly call for a further extension of the WGMP observation period, which could consist in a yearly sampling at only two stations.
(Continental Shelf Research. vol. 298, n° 0278-4343, pp. 105637 (14p.), 01/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UA, CHROME, UNIMES, DYNECO, IFREMER
Seasonal dynamics of cable bacteria in an estuarine intertidal mudflat subject to green tides: Implications for the foraminiferal community and test preservation
As many coastal areas draining intensive agricultural activities, Ledano estuary mudflats (French Brittany) experience Ulva proliferation, causing green tides. We studied the seasonal dynamics of sulphoxidizing cable bacteria from April 2019 to July 2020 using microsensors (O 2 , pH, H 2 S). The activity of these filamentous bacteria, called electrogenic sulphur oxidation (eSOx), results in strong acidification and in pore-water CO 3 2depletion in the first few centimeters of sediment (within the suboxic zone). Living and dead benthic foraminiferal assemblages were studied in July 2020 to observe the effects of eSOx on the calcareous meiofauna and their shell preservation in the sediment. eSOx was patchy on the mudflat but persistent throughout the year. It contributed up to 45% of oxygen consumption during the algal mat decay, and exceeded 100% during the flooding period suggesting stimulation by nitrate inputs. The corrosive effect was maximal in July 2020 (ΔpH ~ 1.7, [CO$_3^{2-}$]calc < 10 μM). The living foraminiferal community was sparse and nearly monospecific, dominated by the calcareous species Haynesina germanica, probably due to green tides coupled with eSOx-driven acidification. However, living specimens of H. germanica showed no signs of advanced dissolution of their shell suggesting a biological capacity to survive in such environmental acidification, potentially linked to their photosynthetic capability. In contrast, the dead assemblages displayed greater diversity despite a loss of about 20% of the calcareous shell recording with depth due to the synergetic effect of low salinity and eSOx. Overall, this study shows that green tides strongly influence cable bacteria activity and then, sedimentary biogeochemical processes in eutrophic coastal environments.
(Journal of Sea Research (JSR). vol. 210, n° 1385-1101, pp. 102683, 01/03/2026)
LPG-ANGERS, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Multi-annual evolution of coastal dunes: Transition from fixed to transgressive dunes state
Most of coastal dunes located in temperate latitudes, especially in the Northern Hemisphere, are relatively stable. However, along the Gironde coast (SW France) substantial dune remobilization has been observed over the last decade following major marine erosion events during the 2013-2014 winter. This study is based on the analysis of a robust dataset including (i) 10 high-resolution Digital Terrain Models (DTMs) derived from airborne LiDAR surveys conducted over a 12-year period (2011-2023) and (ii) 7 Satellite-derived Digital maps of dune vegetation cover derived from Sentinel-2 satellite images acquired between 2017 and 2023. These morphological and biological parameters are linked to forcing parameters derived from observed wind data, to provide a comprehensive analysis of coastal dune changes related to the transition from vegetation-fixed dunes to the development of transgressive dunes. For the first time, morphological and vegetation dynamics are explored over a large spatial scale (tens of km), covering a range of initial dune morphology and sediment supply.
Dunes have transitioned from stable to transgressive states primarily driven by sediment stoss slope recycling process (cannibalism) across a gradient of alongshore variable dune sediment budget, ranging from slightly negative to notably positive (+10 to 15 m 3 /m/yr), Along this coast, transgressive dunes defined as dune migrating via similar stoss and lee slope migration rates, have tripled in number over the last 10 years (reaching ≈ 15 km or 17.3 % of the studied coast). At the center of the Gironde coast where dunes are heavily remobilised, the lee slope of the dune translates landward at a rate of several meters to more than 10 m/year. In the following years, dunes will probably continue to migrate and remobilise across a broader scale if no re-stabilization management plan is implemented.
(CATENA. vol. 264, n° 0341-8162, pp. 109787, 01/03/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, ONF
Storm Wind Flow and Sediment Dynamics on Adjacent Coastal Dunes With Contrasting Morphologies During One Storm Event
This study presents the first high‐resolution spatial and temporal analysis of wind flow, sediment transport and topographic evolution under simultaneous storm conditions across two morphologically contrasting beach‐dune systems, characterized by a gently sloping dune face (11°) and a steep, scarped dune face (36°). Results demonstrate that the dune slope strongly controls near‐surface wind acceleration, the development of secondary airflow structures (amplitude, spatial positions), and the continuity of sediment transport pathways. Over the gentle slope, airflow accelerates progressively up the stoss face, promoting sustained, landward‐directed sediment fluxes across the entire beach–dune system and enabling efficient sediment recycling. In this configuration, beach‐derived contributions account for only 12%–15% of the total sediment flux. In contrast, the steep scarp induces flow deceleration and separation at the dune toe, limiting sediment transfer from the beach and favoring seaward‐directed transport associated with secondary vortices at the crest. These contrasting airflow organizations result in fundamentally different storm responses. The gently sloping dune undergoes landward translation with minimal net volume change, whereas the scarped dune experiences dominant marine erosion, leading to a 4 m retreat of the dune front and a sediment loss of ∼30 m 3 m −1 . A new conceptual model of storm‐driven airflow over contrasting dune morphologies is proposed, illustrating how inherited dune slope governs airflow structure and circulation patterns. Overall, these results identify inherited dune morphology as a primary control on airflow organization, sediment pathways, and dune resilience during extreme events.
(Journal of Geophysical Research: Earth Surface. vol. 131, n° 2169-9003, 02/02/2026)
CEFREM, UPVD, INSU - CNRS, CNRS, BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ONF
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
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
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