Biological features for a minimum conservation reference size revision – case of Ruditapes philippinarum in Arcachon Bay (French Atlantic coast)
The Minimum Conservation Reference Size (MCRS) for marine resources ensure that individuals can mature and reproduce at least once before being caught. For management purposes, MCRS should be revised for specific populations in given areas. In Arcachon Bay (southwest France), fishers have repeatedly requested a review of the MCRS for R. philippinarum. In 2020, a joint recommendation, supported by France, was addressed to the European Commission suggesting a possible reduction in the MCRS of R. philippinarum from 35 mm to 32 mm for Arcachon Bay. This paper provides an overview of the biological features that need to be considered to support such a review, primarily focusing on sexual maturity, individual growth and natural mortality. The reproductive cycle and size at first maturity, estimated at 26.7 mm for the Bay, were found to be similar to other locations in France and in Portugal. The greatest length at which growth slowdown occurred ranges between 24.0 and 31.5 mm with few differences among sites and no significant differences within each site (at hypsometric levels). The natural mortality coefficients were high with 0.67 yr−1 and 0.51 yr−1 for juveniles and adults, respectively. Regarding productivity (resulting from growth and mortality processes) and all methods combined, the optimal balance between individual growth and natural mortality above 30 mm was found at a mean length of 32.2 mm for the intra-lagoon sites and at a mean length of 36.8 mm for the oceanic sites. Based on available information, reducing the MCRS to 32 mm would not threaten population viability. However, the European Commission has raised warning points, which are discussed in light of current regulations in Arcachon Bay.
(Estuarine, Coastal and Shelf Science. vol. 320, n° 0272-7714, pp. 109288, 01/08/2025)
LMAP, UPPA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A coupling approach for long-term 3D morphological evolution of sandy coasts under sea-level rise
This study presents a modular modeling framework for simulating medium- to long-term (decadal to centennial) coastal evolution, focusing on shoreface translation under the combined effects of sea-level rise (SLR) and waves. On these timescales, short-term storm-driven processes are treated as noise superimposed on longer-term trends. We couple the one-dimensional ShoreTrans model, which simulates SLR-driven profile adjustment, with the two-dimensional reduced-complexity model LX-Shore, which captures longshore sediment transport gradients. This coupling enables efficient simulation of three-dimensional morphological change across diverse sandy coastal settings, including environments with dunes, barriers, and hard structures. The framework is first applied to synthetic test cases to explore sensitivity to coupling strategies, then tested on a 5-km beach-dune system in southwest France fronted by a 1.2-km seawall. Results show reasonable agreement with observed shoreline evolution and demonstrate the value of the coupled approach in capturing morphodynamic feedbacks and trajectory shifts not reproduced when shoreline and shoreface processes are modeled independently
(Environmental Modelling and Software. vol. 193, n° 1364-8152, pp. 106624, 01/08/2025)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BW-CGC
Hydrodynamic and Geomorphological Responses of Tidal Flats to Extreme Climate Events
The fate of tidal flats under global climate change is closely tied to ecosystem services and socio-economic development. Nonetheless, there is still a limited understanding of how tidal flats respond to the increasingly frequent and intense extreme weather events. In this study, we conducted a comprehensive hydrodynamic and geomorphological field survey on the Lingang tidal flat in Shanghai during Typhoon In-fa (No. 2106), which allowed us to explore the mechanisms of tidal flat evolution under typhoon and propose insights for sustainable coastal management. Spatially, the vegetation shadow area showed notable sediment deposition, while the windward side of the vegetated zone experienced considerable vegetation loss. Undeveloped channels and depressions acted as sediment sinks, with wider and shallower channels erased by typhoon. Temporally, the differences in tidal flows during the typhoon were closely correlated with changes in wind direction and speed across different typhoon phases. Sediment transport rates during the typhoon were nearly an order of magnitude higher than under calm weather. Based on conceptual model of hydrodynamic and geomorphological processes during typhoons and previous research, we recommend (1) seasonal harvesting of salt marsh vegetation to enhance ecological sustainability while maintaining its wave attenuation function, and (2) spatial planning of artificial salt marsh zones with due consideration of local hydrodynamic patterns to limit vegetation expansion and migration, which could increase maintenance costs. Our findings provide new insights into how tidal flats respond to extreme events and underscore the importance of understanding these geomorphic responses in sustainable coastal management.
(Journal of Hydrology. vol. 656, n° 0022-1694, pp. 133024, 01/08/2025)
ECNU, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, PSL, UVSQ, CEA, INSU - CNRS, X, IP Paris, CNES, SU, CNRS, UPCité, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Depth-Dependent isotope dynamics in karst reservoirs: Multi-Decadal monitoring insights from French caves
Understanding the stable oxygen isotope (δ18O/δD) compositions in rainwater and cave drip water within karst systems is essential for past climatic reconstructions all over the world. However, the relationship between cave drip water isotopes and upper karst infiltrated water and reservoirs remains unclear. Over twenty years, we monitored eight caves in France, from North to South: Arcy-sur-Cure, Villars, Cussac, Pech-Merle, Chauvet, Orgnac, Niaux, and Clamouse, collecting 3,000 dripping water samples from 32 drip points to measure δ18O and δD isotopes. As already observed in many cave sites, the isotopic composition of drip waters shows temporal stability with a Coefficient of Variation (CV) below 7 %, suggesting effective rainfall mixing during infiltration period. However, putting all these data on cave vertical cross sections, we observed subtle decreasing gradients in the averaged dripping δ18O values. For the first time in a multi-cave study, a clear logarithmic decrease of δ18O and δD with depth is found. Deeper sites show more negative isotopic values, especially in shallower zones (<50 m). In order to better understand these gradients, we used the hydrologic KarstFor model which revealed the importance of overflow mechanisms and of evapotranspiration (ETP) in driving this depth-dependent isotopic effect. These findings emphasize the significance of incorporating depth-dependent reservoir dynamics when analyzing isotopes in cave environments, advocating for a nuanced understanding of karst hydrological processes in affecting stalagmite δ18O.
(Journal of Hydrology. vol. 656, n° 0022-1694, pp. 133028, 01/08/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GLACCIOS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEOTRAC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
In situ analysis of single secondary organic aerosol from the ozonolysis of α-pinene using laser trapping and Raman spectroscopy
To form secondary organic aerosols (SOAs) from volatile α-pinene via ozone oxidation reactions, the generation of low-vapor pressure compounds capable of acting as condensation nuclei is essential. Both laboratory and field studies have identified low-volatile dimers as key components in SOA formation. Although mechanisms involving stabilized Criegee intermediates and peroxy radicals have been proposed for dimer formation in the gas phase, the detailed processes of SOA formation remain widely debated due to the high diversity of reaction products and the inherent complexity of their formation mechanisms. To clarify certain steps of the SOA formation mechanism from ozone-initiated oxidation of α-pinene, a laser trapping technique coupled with Raman spectroscopy was employed for in situ analysis of individual SOA particles. In this study, single micrometer-sized α-pinene SOA particles were successfully trapped in air. To our knowledge, this represents the first successful application of laser trapping of α-pinene SOA particles directly in air. An intense Raman peak observed at about 852 cm−1 was attributed to the O–O stretching vibration of peroxides. This finding provides direct evidence for the presence of peroxy functional groups in the dimers, likely formed via stabilized Criegee intermediates. These results demonstrate the capability of laser trapping combined with Raman spectroscopy to detect specific molecular features, such as peroxide bonds, within α-pinene-derived SOAs in air.
(Chemosphere. vol. 385, n° 0045-6535, pp. 144581, 29/07/2025)
HU, ISM, UB, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A continuous 500‐year sediment record of inundation by local and distant tsunamis in South‐Central Chile (40.1°S)
Abstract Chile's west coast is frequently struck by megathrust earthquakes and tsunamis, as illustrated by the CE 2010 Maule ( M w 8.8) and CE 1960 Valdivia ( M w 9.5) events. Despite numerous palaeoseismic and palaeotsunami studies, uncertainties remain regarding the rupture extent and tsunamigenic potential of M w 8–9 earthquakes. This study examines the sedimentary record of Laguna Gemela West, a coastal lake at 5–6 m a.s.l. and of 17.5 m depth. It is separated from the Pacific by a 400 m long channel bordered by northward‐propagating dunes and controlled by Pleistocene sandstones forming a knickpoint in the channel profile. Multiple sedimentary proxies (e.g. grain‐size, X‐CT, XRF scanning) identified five distinct sand‐enriched layers, interpreted as tsunami deposits. Age‐depth modelling (based on 137Cs and 14C) allowed linking these deposits to the CE 2010, 1960, 1837, 1737 and 1575 megathrust earthquakes. While historical records confirm significant tsunamis in CE 2010, 1960, 1837 and 1575, no reports exist for a CE 1737 tsunami. However, a potential tsunami deposit and evidence for subsidence were found at the nearby Chaihuín site, albeit with large dating uncertainty (CE 1600–1820). The more precise age for a sand layer at Laguna Gemela West (CE 1672–1746) supports the occurrence of a local tsunami in CE 1737. Additionally, deposits linked to the CE 1837 and 2010 events suggest tsunamis can impact sites >100 km adjacent to megathrust ruptures. A second pulse in the uppermost sand layer may reflect the CE 2011 Japan tsunami, which reached a similar height (~1.6 m a.s.l.) in the nearest tide gauge as the CE 2010 tsunami. Unlike coastal plain sites, which often require coseismic subsidence for deposit preservation, coastal lakes can capture a more complete tsunami history. This study highlights their complementary role in palaeotsunami research, providing insights in local, regional and transoceanic tsunami events.
(Depositional Record, n° 2055-4877, 28/07/2025)
UGent, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ICT
Benchmarking shoreline prediction models over multi-decadal timescales
Robust predictions of shoreline change are critical for sustainable coastal management. Despite advancements in shoreline models, objective benchmarking remains limited. Here we present results from ShoreShop2.0, an international collaborative benchmarking workshop, where 34 groups submitted shoreline change predictions in a blind competition. Subsets of shoreline observations at an undisclosed site (BeachX) over short (5-year) and medium (50-year) periods were withheld from modelers and used for model benchmarking. Using satellite-derived shoreline datasets for calibration and evaluation, the best performing models achieved prediction accuracies on the order of 10 m, comparable to the accuracy of the satellite shoreline data, indicating that certain beaches can be modelled nearly as well as they can be remotely observed. The outcomes from this collaborative benchmarking competition critically review the present state-of-the-art in shoreline change prediction as well as reveal model limitations, facilitate improvements, and offer insights for advancing shorelineprediction capabilities.
(Communications Earth & Environment. vol. 6, n° 2662-4435, pp. 581, 24/07/2025)
UNSW, USGS, TU Delft, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, UC / UniCan, CSIRO, ULISBOA
Effects of high overvoltages on the treatment of PFAS in water
The chemical structure of per-polyfluoroalkyl substances (PFAS), based on strong C-F bonds makes them extremely stable in the natural environments. Plasma technologies have a strong potential for degrading PFAS in water. Understanding of the plasma removal mechanisms is necessary to improve the efficiency and to better control the by-products. Here three types of discharges with the same deposition energy were investigated for plasma removal of PFAS. An AC and a nanosecond high voltage pulse discharge were used in a wire-to-water surface configuration, whereas an atmospheric pressure fast ionization wave was generated in a 3-pins configuration over the water surface.
(20/07/2025)
EM2C, CNRS, LSPM, USPC, CNRS, LPTC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Water Wars: competition between native and exotic isoetid species
Among several global changes, invasion by exotic species is often pointed out as responsible for the decline of native species. Indeed, in the competition for space and resources, fast-growing species are generally more efficient than native ones. The natural lakes along the Aquitaine coast are home to unique and protected populations of isoetid macrophytes, which are declining in the last decades. The present study aims at testing the potential competition between the native isoetid Lobelia dortmanna and the exotic isoetid Sagittaria graminea, both coexisting in Lake Cazaux-Sanguinet, France. To achieve this, we set up a multi-year monitoring program across 1x1m quadrats, with three conditions: native species only, exotic species only, and mixed condition when both species occurred. Each individual in the quadrat was spatially mapped and its photosynthetic activity was measured, as well as its leaf length and width. Sediment samples were also collected to analyze differences in organic matter content and granulometry between the quadrats. Preliminary results show that, while substrate analysis indicates similar biotopes for both species, their co-occurrence triggered significant physiological and morphological responses. Additionally, the native and exotic species appeared to follow different patterns of spatial distribution. However, these first results did not necessarily indicate a negative effect of the exotic species on the native one. Further field sampling in the coming years will help clarify the temporal spatial dynamics of the two species.
(20/07/2025)
UR EABX, INRAE, ECLA, USMB [Université de Savoie] [Université de Chambéry], INRAE, OFB, LPTC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Persistence of a wind-driven fire regime in Mediterranean France over the past 8200 years revealed by a marine paleoecological record
Data on paleofire activity in southeastern France during the Holocene are still lacking thus limiting our capability to anticipate fire regime shifts under climate change. Here, we present a 8.2 ky-long high-resolution time-series of microscopic charcoal (microcharcoal) particles from a marine sediment core retrieved from the Rhone prodelta, in the Gulf of Lions (NW Mediterranean Sea). Fire frequency, episodes, size and types of burnt vegetation were determined by quantifying microcharcoal and analysing its morphometry. Our results indicate an increase in biomass burning and fire frequency combined with a decrease in the mean elongation ratio from the Northgrippian (8.2–4.2 ka) to the Meghalayan (4.2–0 ka) stage. This pattern is interpreted as reflecting a shift from the burning of graminoids in closed mesophytic forests during the Northgrippian to the burning of shrub communities in open Mediterranean habitats during the Meghalayan. We also identified 20 fire episodes over the past 8.2 ka, occasionally coinciding with human occupations. Large fires occurred during cold events and summer droughts conditions of the Northgrippian. We relate this finding to negative phases of the North Atlantic Oscillation (NAO) and increased fuel load under wet winter conditions and fuel flammability under dry and strong summer winds. Besides climate and vegetation, human activity is likely to be an additional driver of fire during the Meghalayan. Southeastern France is currently identified as a region with a high wind-driven fire risk, although its fire regime analysis is biased by intensive fire suppression. We suggest that wind-driven large fires is an inherent element of fire and weather patterns in this area rather than the result of fire suppression strategies leading to uncontrollable large fires.
(The Holocene. vol. 35, n° 0959-6836, pp. 961-976, 13/07/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEFE, EPHE, PSL, CNRS, IRD [Occitanie], INRAE, Institut Agro, UM, UMPV, IMBE, AU, AMU, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, UMLP, LCE, CNRS, UFC, UBFC, LOCEAN-VOG, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, EPOC