From fixed to transgressive coastal dunes, the conditions and timing of the transition along the Aquitaine coast, France
Today most of the coastal dunes in temperate latitudes, especially in the northern hemisphere, are relatively stable. However, over the last decade, the Gironde coast has experienced substantial dune remobilization following a major marine erosion event. The qualities of the dataset used (continuity in time and space) based on annual airborne LiDAR and Satellite imagery (Sen-tinel-2) allow a detailed description of the morphological change and establish relations with forcing and controlling factors (vegetation cover, geomorphological descriptors). Between 2014 and 2023, about 10 km of the Gi-ronde dunes have switched from fixed dunes to transgressive dunes. The analysis showed that in the vast majority of the cases the dominant process involved was dune front cannibalism. However, there is considerable spatial and temporal variability in the transition to a transgressive dune along the coast, depending on the amount of sediment remobilized and the morphological parameters of the dunes (steepness of the front slope, width).
(07/04/2025)
BRGM, UB, UPVD, ONF, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Observations and modelling of coastal dune dynamics along the Gironde Coast, France
Considered as reservoirs of biodiversity, coastal dunes also represent natural barrier against coastal flooding and large source of sediment to mitigate coastal erosion. Dynamics of coastal dunes are forced and controlled by marine, aeolian and biological processes. A better understanding of the interactions between all these processes based on field observations or numerical modelling is crucial to define management strategies that aim to develop the resilience of coastal dune against sea level rise. The analysis of multi-annual topographic data collected along the Gironde coast in SW France show a strong landward migration of the coastal dunes caused by strong wind events and a decrease in vegetation cover. The same data were also used to calibrate and validate a numerical model, AeoLiS, that simulated Aeolian sediment transport. This model showed good performance to reproduce the landward migration of non-vegetated dune.
(07/04/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Modelling Microplastic Dynamics in Estuaries: A Comprehensive Review, Challenges and Recommendations
Abstract. The study of microplastic transport and fate in estuaries poses significant challenges due to the complex, dynamic nature of these ecosystems and the diverse characteristics of microplastics. Process-based numerical models have become indispensable for studying microplastics, complementing observational data by offering insights into transport processes and dispersion trends that are difficult to capture through in-situ measurements alone. Effective model implementations require an accurate representation of the hydrodynamic conditions, relevant transport processes, particle properties, and their dynamic behaviour and interactions with other environmental components. In this paper, we provide a comprehensive review of the different process-based modelling approaches used to study the transport of microplastics in estuaries, including Eulerian Idealized 2DV models, Eulerian Realistic Models, Lagrangian Particle Tracking Models, and Population Balance Equation Models. We detail each approach and analyze previous applications, examining key aspects such as parameterizations, input data, model setups, and validation methods. We assess the strengths and limitations of each approach and provide recommendations, good practices, and future directions to address challenges, improve the accuracy of predictions, and advance modelling strategies, ultimately benefiting the research field.
(Geoscientific Model Development. vol. 18, n° 1991-9603, pp. 7227-7255, 07/04/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SIAME, UPPA, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS
Impact of a pulsed light process on phytosanitary products and ecotoxicity of viticultural wastewaters
Pulsed light (PL) treatment of three viticultural wastewaters (WWs) was performed with increasing fluence from 0 to 91 J/cm 2 . The evolution of the concentrations of the pesticides was monitored by High-Performance Liquid Chromatography coupled with tandem Mass Spectrometry (HPLC-MS/MS). PL enabled a significant decrease in concentration of the majority of the pesticides present in the wastewaters (WW): 6 out of 12 pesticides were degraded by 62 to 92 % in WW1, 7 out of 10 by over 80 % in WW2, and the only pesticide observed, fluopicolide, was degraded by 87 % in WW3. Only four pesticides were not significantly affected by PL: ametoctradin, benalaxyl, dimethomorph and tebuconazole. PL treatment was found to be less effective on wastewater than on pesticide-spiked deionised water, likely due to the wastewater matrix components absorbing the radiation. Fifteen of the 36 targeted photoproducts were observed following PL treatment of wastewater. The main potential reactions of the halogenated compounds were dehalogenation or substitution of halogen by hydroxyl groups. A photoproduct and possibly natural metabolite of fenbuconazole (m/z 303) was observed in an untreated sample. Acute toxicity tests were performed on the bacteria A. fischeri. A significant reduction in toxicity was observed in the three tested wastewaters: by a factor of 4.1, 6.5 and 4.3 in WWs 1, 2 and 3 respectively. However, the wastewaters remained highly toxic even after the highest fluence applied, probably due to very high copper concentrations in the three wastewaters, and to the absorbance of the samples reducing the degradation efficiency of the PL. Further studies should focus on adapting PL treatment to wastewater; the first step should be a pilot study performed on a semi-industrial scale. Toxicity analyses should be carried out on various freshwater trophic levels to ensure the harmlessness of the process.
(OENO One. vol. 59, pp. 8346, 03/04/2025)
OENO, UB, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB
Global impoverishment of natural vegetation revealed by dark diversity
Anthropogenic biodiversity decline threatens the functioning of ecosystems and the multiple benefits they provide to humanity1. Besides causing species losses in directly affected locations, human influence might also reduce biodiversity in relatively unmodified vegetation if far-reaching anthropogenic effects trigger local extinctions and hinder recolonisation. Here, we show that local plant diversity is globally negatively related to the level of anthropogenic activity in the surrounding region. Impoverishment of natural vegetation was only evident when we considered community completeness: the proportion of all suitable species in the region that are present at a site. To estimate community completeness, we compared the number of recorded species with the dark diversity — ecologically-suitable species that are absent from a site but present in the surrounding region2. In the sampled regions with minimal Human Footprint Index, an average of 35% of suitable plant species were present locally, compared with less than 20% in highly-impacted regions. Besides the potential to uncover overlooked threats to biodiversity, dark diversity also provides guidance for nature conservation. Species in the dark diversity remain regionally present, and their local populations might be restored through measures that improve connectivity between natural vegetation fragments and reduce threats to population persistence.
(Nature. vol. 641, n° 0028-0836, pp. 917-924, 02/04/2025)
U of S, UNIBO, MU / MUNI, CSIC, UV, UC Davis, UC, NINA, UNSW, FUM, NRCan, UAM, JCU, UHasselt, UiB, UPV / EHU, UB, UNCG, UNC, NUM, ESALQ, USP, MMU, UdeS, IPE - CSIC, CSIC, UNIVAQ, UNIPR, EPHE, PSL, LEHNA P3E, LEHNA, UCBL, ENTPE, CNRS, Uninsubria, UR EFNO, INRAE, CEN, UC, CAS, UNESP, HUN-REN, SGGW, ZHAW, CREAF, CSIC, UAB, IMBIV, CONICET, FCEFyN, iDiv, IB-CAS, CAS, UNIBE, TRU, UFRGS, UMR Eco&Sols, Cirad, IRD, INRAE, Institut Agro, UMR ECOFOG, Cirad, UG, CNRS, UA, INRAE, CRBE, IRD, CNRS, Toulouse INP, Comue de Toulouse, EPE UT, Comue de Toulouse, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Opportunities for Earth observation to inform risk management for ocean tipping points
As climate change continues, the likelihood of passing critical thresholds or tipping points increases. Hence, there is a need to advance the science for detecting such thresholds. In this paper, we assess the needs and opportunities for Earth Observation (EO, here understood to refer to satellite observations) to inform society in responding to the risks associated with ten potential large-scale ocean tipping elements: Atlantic Meridional Overturning Circulation; Atlantic Subpolar Gyre; Beaufort Gyre; Arctic halocline; Kuroshio Large Meander; deoxygenation; phytoplankton; zooplankton; higher level ecosystems (including fisheries); and marine biodiversity. We review current scientific understanding and identify specific EO and related modelling needs for each of these tipping elements. We draw out some generic points that apply across several of the elements. These common points include the importance of maintaining long-term, consistent time series; the need to combine EO data consistently with in situ data types (including subsurface), for example through data assimilation; and the need to reduce or work with current mismatches in resolution (in both directions) between climate models and EO datasets. Our analysis shows that developing EO, modelling and prediction systems together, with understanding of the strengths and limitations of each, provides many promising paths towards monitoring and early warning systems for tipping, and towards the development of the next generation of climate models.
(Surveys in Geophysics. vol. 46, n° 0169-3298, pp. 443–502, 01/04/2025)
MOHC, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], LOCEAN-PROTEO, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, ISMAR, CNR, PIK, GEOMAR, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, JAMSTEC, NPS, GISS, GSFC, OCCR, UNIBE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Chaetoceros Resting Spores Do Not Significantly Bias Sedimentary Diatom‐Bound Nitrogen Isotope Records Despite Distinctly Low Values
Abstract The nitrogen isotopic composition of diatom frustule‐bound organic matter (δ 15 N DB ) is often used to study changes in high latitude biological pump efficiency across glacial‐interglacial cycles, but the proxy may be biased by species‐specific effects. The genus Chaetoceros is of particular interest because of its abundance throughout ocean basins, its shifting biogeography during glacial periods, and the ability of many species to form heavily silicified resting spores. Here we investigate how Chaetoceros resting spores (CRS) record surface nitrate conditions in their nitrogen isotopic composition, and thus impact δ 15 N DB records, using assemblage‐specific sedimentary δ 15 N DB measurements and laboratory culture experiments. We find that fossil CRS from ODP Site 1098 record δ 15 N DB values 1.1–7.8‰ lower than non‐CRS diatoms in sediment. CRS grown in culture yield consistent results, recording δ 15 N DB values 2.6–8.2‰ lower than vegetative Chaetoceros in the same cultures. Low values are attributed to assimilation of isotopically light ammonium, heavy silicification, and/or internal nitrogen allocation processes during sporulation. Applying these findings to published δ 15 N DB records, variable CRS relative abundance in open ocean glacial sediments does not significantly bias δ 15 N DB records across glacial‐interglacial cycles, despite the large δ 15 N DB difference observed in CRS versus non‐CRS diatoms, due to the spores' small size.
(Paleoceanography and Paleoclimatology. vol. 40, n° 2572-4525, 01/04/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Is the European regulatory model for predicting worker exposure conservative? Comparison of predicted and measured under usual working conditions exposures in fruit growing
Introduction: Pesticide exposure increases the risk of chronic disease among farmers. Understanding exposure is necessary for epidemiological and regulatory purposes. In Europe, worker exposure is assessed during the registration process using the OPEX model, which is based on a limited number of studies, often unpublished and carried out by pesticide companies. We assessed the conservativeness of OPEX for workers performing post-application tasks (re-entry, harvesting).Methods: In 2016-2017, dermal exposure to captan/THPI and dithianon was measured in French fruit farm workers during 65 re-entry (net folding and deployment, thinning, tying) and 58 harvesting days, using patches and cotton gloves. We used linear regression to compare measured and corresponding OPEX-calculated exposure using 1) default parameters; 2) field parameters (actual task duration, measured dislodgeable foliar residues) for 20 observations.Results: Workers were exposed several days after the last application, which is not considered in the pesticide registration process. We found that the model underestimated exposure calculated with field parameters in all observations for dithianon and 60% for captan, linked to an underestimation of OPEX transfer coefficients (ratio of 0.40 for captan and 0.26 for dithianon between default and measured transfer coefficients).Discussion: When observation occurred several days after application, OPEX tended to underestimate exposure. An industry study conducted under controlled working conditions found divergent results. It seems important to include field studies conducted under usual working conditions in the registration process to ensure a truly conservative approach and to consider cumulative exposure, since post-application tasks account for around 600 working hours a year.
(Environmental Research. vol. 271, n° 0013-9351, pp. 121042, 01/04/2025)
UNICAEN Santé, UNICAEN, NU, ANTICIPE, UNICAEN, NU, CHU Caen Normandie, NU, UNICANCER/CRLC, NU, INSERM, BPH, UB, INSERM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LABÉO, ANTICIPE, UNICAEN, NU, CHU Caen Normandie, NU, UNICANCER/CRLC, NU, INSERM, PRISMM, PLATON, UNICAEN, NU, UNICAEN, NU, UNICANCER/CRLC, NU
Enigmatic Deep‐Water Seafloor Depressions East of Tortue Island, Northern Haiti Margin
A widespread area of seafloor depressions -circular, arcuate to elongated-shaped -has been found along the Northern Haitian coast, at water depths between 600 and 2,000 m. Characterized by wavelengths spanning several hundred meters and heights of tens of meters, these depressions are linked with a series of narrow ridges boasting varied morphologies. Our analysis integrating multichannel seismic reflection, highresolution bathymetry data, and sedimentological and geochemical evaluations of surface sediment cores indicates that present-day seafloor morphology results from the interaction of slope bottom currents with the seafloor. The analyzed sediment cores exhibit hemipelagites, silty and sandy contourites, fine-grained turbidites and reworked sand layers, implying sedimentation in a contourite drift system. This is further corroborated by seismic reflection data depicting wavy reflectors and aggradational stacking features typical of contourite drifts. Seafloor depressions are likely erosional features formed on the top of a contourite drift formed by the interaction of bottom currents with an irregular seafloor morphology. The seafloor equilibrium was initially disturbed by mass-wasting events. Subsequently, the quasi-steady flow of along-slope bottom currents influenced sedimentary distribution and controlled the morphology of the seafloor depressions-constant reshaping through erosion on their flanks. The resulting rough seafloor could have facilitated the destabilization of bottom currents and the development of erosive eddies responsible for the current morphology of the seafloor depressions. This study highlights the interplay between sedimentary processes (accumulation and compaction) and bottom currents, showing how their combined effects influence slope sedimentation and seafloor geomorphology, forming unique erosional features.
Plain Language Summary Between 600 and 2,000 m of water depth, the seafloor of the northern Haiti margin presents a field of sub-vertical to elongated depressions. Scientific investigations dealing with the nature of the seafloor material and subsurface structure revealed that such peculiar seafloor morphologies are not related to fluid escape features but to the interplay between sedimentary processes and water masses currents. A submarine landslide triggered in the past has likely created a rough seafloor resulting in the destabilization of currents linked to the deep water masses, enhancing seafloor erosion and deposition.
(Geochemistry, Geophysics, Geosystems. vol. 26, pp. e2024GC012089, 01/04/2025)
iSTeP, INSU - CNRS, SU, CNRS, CY, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFPEN, UCM, UEH
Quantifying the relative contributions of forcings to the variability of estuarine surface suspended sediments using a machine learning framework
The influence of forcing mechanisms on the variability of suspended sediments in an estuary is, for the first time, synoptically quantified over prevailing ('normal') conditions and extreme events. This study investigates the complex and non-linear influence of tides, river discharge, and winds on the variability of suspended sediments in the macrotidal Gironde Estuary, France. Employing a machine learning-based framework, we integrated high-frequency field data, hourly numerical modeling outputs, and semi-daily satellite remote sensing to spatially quantify the relative contributions of forcing mechanisms. Our results reveal that tides are the primary driver of sediment variability (42.3–58.9%), followed by river discharge (21.2–34.7%) and wind (8.7–16.9%). Uncertainties range between 7% and 13.6%. In addition, the spatial variability of their contributions is consistent across numerical modeling and satellite remote sensing data, with differences not exceeding 10%. However, satellite data is limited by cloud cover and may miss extreme events. In contrast, hourly numerical modeling indicates tides are the dominant forcing mechanism under extreme events significantly affecting suspended sediment variability in the estuary. This study verifies the effectiveness of our machine learning approach against traditional Singular Spectral Analysis using field data. We demonstrate that machine learning techniques can effectively synthesize spatial distribution patterns of hydrodynamic and sedimentological variability, including the influence of winds. Our findings highlight not only the potential of satellite observations to analyze prevailing conditions despite data gaps but also that with hourly numerical modeling, the impact of forcings can be synoptically quantified under prevailing ('normal') conditions and extreme events.
(Continental Shelf Research. vol. 287, n° 0278-4343, pp. 105429, 01/04/2025)
DYNECO, IFREMER, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], FURG, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, NIOZ