New insights in benthic biodiversity of the saya de Malha Bank
(Deep Sea Research Part II: Topical Studies in Oceanography. vol. 222, n° 0967-0645, pp. 105500, 01/08/2025)
ISYEB, MNHN, EPHE, PSL, SU, CNRS, UA, AIM (UMR_7158 / UMR_E_9005 / UM_112), CEA, INSU - CNRS, CNRS, UPCité, LECOB, SU, CNRS, OOB, SU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, PSI
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
Evolución tridimensional del frente dunar de la playa de l’Auir (2008-2022)
Las dunas son espacios interrelacionados con las playas que presentan un elevado dinamismo y un gran interés ambiental y social. Su estudio a grandes escalas espaciales y temporales se encuentra limitado por la dificultad de obtener datos altimétricos precisos de forma eficiente. Su caracterización tridimensional empleando técnicas de teledetección resulta de gran interés para cuantificar los cambios sedimentarios y analizar el conjunto del sistema playa-duna. Los vuelos LiDAR, junto al reciente desarrollo métodos fotogramétricos de reaprovechamiento de fotografías aéreas, permiten la obtención de series históricas de datos tridimensionales de alta precisión del frente costero. Se ha caracterizado la evolución del frente dunar de la playa de l'Ahuir, en Gandia (Valencia), a partir de cambios volumétricos y caracterización morfométrica derivada de perfiles tomados, a su vez, sobre 9 modelos digitales de superficie entre 2008 y 2022. Los resultados muestran una fase de importantes ganancias sedimentarias durante el periodo 2009-2015 (más de 12000 m3), que aparece asociada a un periodo de relativamente baja intensidad en los temporales costeros. Posteriormente, y pese a la alternancia de ligeras ganancias y pérdidas de sedimento en la playa emergida entre los MDS anuales, el frente dunar se encuentra en una fase de estabilidad y ligeras ganancias, presentando una ganancia neta de cerca de 26000 m3 para el conjunto del periodo 2008-2022. A diferencia de otros cordones dunares de la costa valenciana, el sector de l’Ahuir no se ha visto erosionado de forma asociada al temporal Gloria en enero de 2020. El análisis aporta información morfológica de gran interés para la caracterizar el estado sedimentario de la playa de l’Ahuir y monitorizar sus cambios, demostrando su potencial para suministrar datos de gran precisión y con gran cobertura espacial y temporal.
(Revista de Teledetección, n° 1133-0953, 31/07/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
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
Lack of data and misperception of open science limit the scope of Cantabrian brown bear body mass studies, not misinterpretation of results: Reply to comment by García-Vázquez (2025)
This manuscript responds to the comment of García-Vázquez on our recent paper, especially regarding the decline in body mass of the Cantabrian brown bear during the Holocene. The observations of García-Vázquez are reviewed point by point, addressing methodological aspects, that is, the use of the Viranta equation, the mass estimation of the specimen SH5-97-T29-35 and radiocarbon dating, as well as her ethical questions about the use of previously published data. Re-evaluations show that (1) the errors noted do not significantly affect the original conclusions of Fidalgo et al. and, (2) the use of thirdparty data was carried out in compliance with both legal regulations and open science principles. The new analyses maintain the pattern of declining bear body size after 7000-4500 years ago, without any conclusive evidence to link this phenomenon to the introduction of firearms in historical times. Neither this nor any alternative hypotheses are discarded, though. The importance of integrative meta-analyses in data-poor contexts is highlighted, and their legitimacy in the framework of collaborative and open science is defended, provided that sources of data are cited.
(The Holocene. vol. 35, n° 0959-6836, pp. 1196 - 1199, 29/07/2025)
MNCN, CSIC, NMBU, IDEES, UNICAEN, NU, ULH, NU, UNIROUEN, NU, CNRS, IRIHS, UNIROUEN, NU, 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
Down in the dungeons: the hidden role of diatom biofilms and microbial activity in the biogeochemistry of a dynamic estuarine point bar
ABSTRACT In many estuaries, biogeochemical investigations have often focused on transient diatom biofilms that form on low‐energy intertidal flats. Studies on microphytobenthos in high‐energy sedimentary environments are unusual. The present investigation focuses on the biogeochemistry to a depth of 6 m of a fluvio‐estuarine point bar from the Garonne channel (SW France) impacted by both tidal current and tidal wave, where three sediment cores were taken. Porewater chemistry was analysed with microelectrodes (pH, oxygen and sulfide), ion chromatography and inductively‐coupled‐plasma spectrometry (for major elements) and colorimetric assays (for iron speciation). Porewater composition was compared to measurements of microbial activity including isothermal calorimetry and metabolic assays using triphenyltetrazolium chloride and fluorescein diacetate to determine the distribution of predominant microbial metabolisms in the sediment. Finally, bulk sediment chemistry was characterized through X‐ray fluorescence core scanning. Sediments are heterolithic, made of decimetre to meter thick alternating sand and mud. The uppermost 60 cm of the point bar sediment show a mostly classical vertical succession of microbial metabolisms: (i) oxygenic photosynthesis occurs mostly in diatom biofilm forming in the uppermost millimetres; (ii) aerobic respiration between 0 cm and 1 cm, (iii) nitrate reduction between 6 cm and 16 cm, partially overlapping (iv) sulfate reduction between 10 cm and 25 cm, (v) manganese oxide reduction below 2 cm and (vi) iron oxide reduction below 16 cm. Measurements of metabolic activity, elevated in areas showing significant geochemical changes, confirmed the impact of microbial metabolism on the composition of pore water. The highest metabolic activity coincides with areas where oxygen, nitrate and sulphate concentrations are decreasing. Hydrolytic activity peaked in the zone of aerobic respiration, possibly in part due to enzymatic degradation of organic matter (e.g., extracellular polymeric substances) produced in surface diatom biofilm. Low concentrations of nitrates and sulfates were measured in sands at 1.3 to 1.6 m and 3.2 m depth, coinciding with a renewed increase in hydrolytic activity and metabolically active cells. Because of the sediment heterolithic composition and the point bar architecture made of laterally accreting layers, subsurface advection of porewater through permeable horizons could explain the local increases of nitrate and sulfate reduction. Impacts of microbial metabolism on early diagenesis were modelled using PHREEQC software and outcomes predicted the potential precipitation of metastable iron and/or sulfides. This was confirmed by X‐ray fluorescence analyses showing a coinciding increase of sulfur, Fe and/or Mn at several depths (e.g., 15 to 60 or 560 to 580 cm). Based on our observations, we propose a biogeochemical model that links microbial metabolisms and early diagenesis to the complex vertical sedimentary architecture of an estuarine point bar. Our results show that high‐energy estuarine point bars are subject to an active biogeochemical cycling of C, S, N, Fe and Mn quite similar to that of intertidal mudflat, but locally altered by the sedimentary architecture of the point bar, resulting in lateral advection of porewater.
(Sedimentology. vol. 73, n° 0037-0746, pp. 1244-1270, 24/07/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, Unibas, GEOPS, INSU - CNRS, CNRS, UCONN
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