Influence of meteo-marine forcings on groundwater level fluctuations of a coastal multi layer aquifer
A multi-layered aquifer made up of alluvial formations from the Quaternary, overlying levels of Pliocene sands and clays is located beneath the Roussillon plain (Perpignan, France). Covering an area of 800 km² and up to 300 m thick on land, this aquifer extends several dozen kilometres beneath the Mediterranean Sea. It contains a freshwater resource which, at a greater or lesser distance from the shoreline, is likely to be mixed with seawater. A hydrogeophysical observatory (Dem'Mer) has been set up along the coastline for monitoring the piezometric and physicochemical (conductivity, temperature) behavior of the groundwater flowing through the various permeable levels described within this multi-layer aquifer. The time series of groundwater levels obtained from this observatory for several years have been processed using spectral analysis to explore the seasonal to daily influence of meteomarine forcings (seawater level, tides, storms) on groundwater flows. Complementary, crosscorrelation and coherence analyses have been performed to identify how the different signals are organised over time. This work provides field evidence of the influence of storm waves forces at sea bottom, water level at the shoreline and tide on the piezometric fluctuations in the aquifer nearby the coast. The results obtained constitute constraints that can be incorporated into the modelling work currently underway on this aquifer.
(02/06/2025)
BRGM, UM, UMR G-EAU, Cirad, BRGM, IRD, INRAE, Institut Agro, UM, INSU - CNRS, CNRS, UA, UM, SMNPR, UNINE, UniFE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB
Numerical investigation of seasonal wind-wave responses to severe seagrass decline in a coastal lagoon
The intensification of environmental stressors and anthropogenic pressures has resulted in significant seagrass loss worldwide, reducing the capacity of vegetation to damp hydrodynamic energy. While the broad-scale impact of seagrass decline on wind waves has been partially investigated in coastal lagoons, the role of seasonal variations in seagrass characteristics in influencing these responses remains not fully understood. We propose to explore the seagrass-wave interaction through the implementation of a novel coupled wave-flow-vegetation model, which considers deflected canopy height in WAVEWATCH-III, and applied to the Arcachon lagoon. We perform a scenario analysis using different wind conditions and various maps of seagrass coverage (from 1989 to 2016) to provide new insights into how seasonality affects wind wave responses to Zostera noltei decline. Our results reveal that during the summer, when seagrasses are fully developed, seagrass decline significantly reduces the ability of Z. noltei to dissipate wave energy, leading to a wave height increase (reaching 30 %, for H m0 between 0.05 m and 0.35 m) in the areas where seagrass coverage is most reduced. However, during the winter, when canopy height and density are low, no significant changes in wave dissipation are observed due to Z. noltei decline. This study also shows that modifications of the ambient current within the canopy further decreases the capacity of Z. noltei to attenuate waves, as the intensification of flow conditions due to seagrass decline reduces canopy height
(Coastal Engineering. vol. 201, n° 0378-3839, pp. 104796, 01/06/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LERAR, COAST, IFREMER, BRGM
Shoulder to shoulder architecture of a salt-related rift basin at the onset of continental break-up: The Central High Atlas Jurassic diapiric province (Morocco)
Continental passive margins are often defined by early salt-related rift systems buried beneath thick sedimentary piles, with structural and sedimentary architectures only directly observable when inverted in orogenic systems where primary salt structures are overprinted by compression. The Central High Atlas diapiric province (Morocco) is an inverted salt-related rift basin with active salt tectonics since early Mesozoic times that provides an exceptional view of early syn-rift sediments and structure. We present the first regional balanced and restored cross-sections of the Central High Atlas evidencing the role of salt tectonics. The cross section includes seven salt walls and six minibasins, with associated Early Jurassic to Cenozoic halokinetic strata that indicates a shortening of 38 km (24%). The Jurassic rifting stage is characterized by shallow water sediments along the basin margins and around localized salt walls, separated by minibasins filled with deep-water sediments undergoing higher subsidence rates. Subsequently, a longitudinal deltaic system prograded eastwards coevally with shallow marine deposition associated with active salt walls. Thus, local diapir uplift enhanced shallow-water deposition and local aerial exposure in central parts of the basin throughout the whole rifting stage. These features provide insights for the study of rift basins and the early stages of continental break-up worldwide, and for the exploration and production of hydrocarbons in equivalent settings.
(Marine and Petroleum Geology. vol. 176, n° 0264-8172, pp. 107338, 01/06/2025)
UAB, UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Field measurements of wave and flow dynamics along a high-energy meso-macrotidal coast adjacent to a large estuary mouth
The North-Médoc coast, located to the south of the Gironde estuary, exhibits complex hydrodynamic conditions driven by high-energy incident waves and large tides, which are influenced by large-scale rocky outcrops, shoals, and tidal channels on the inner shelf. These wave- and tide-driven hydrodynamics result in rapid morphological changes, with shoreline erosion peaking locally at 5 m/year. In autumn 2022, an intensive two-week field campaign was conducted along three cross-shore transects distributed across the North-Médoc coast to, for the first time, document and analyze the hydrodynamics in this area. The campaign involved collecting measurements of waves and currents across both the inner shelf and nearshore regions, using six current profilers and 13 pressure sensors. Tides were found to predominantly modulate wave transformation and flow in both the nearshore and inner shelf regions of the North-Médoc coast. Strong alongshore currents were measured across the entire study site, increasing southward, which is linked to the overall morphology of a tidal channel. Tidal currents are flood-dominated in the northern part and ebb-dominated in the southern and central parts of the study area. Total currents and wave heights are modulated by tidal elevation, with, for example, increased wave height at the coast during higher tide levels. Nearshore waves, which undergo complex transformation across the inner shelf, such as wave refraction over shoals and rocky outcrops, also drive longshore currents in the surf zone, superimposed on the tidal current. These conditions result in a strong, net, northeastward longshore current, even during low-energy wave conditions. These observations provide new insights into the hydrodynamics of this rapidly evolving coastline and establish a comprehensive dataset that will be crucial for the development and validation of process-based and reduced-complexity models in this region
(Estuarine, Coastal and Shelf Science. vol. 317, n° 0272-7714, pp. 109205, 01/06/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM, LIENSs, INSU - CNRS, ULR, CNRS
PBK-TD modelling of the gonadotropic axis: Case study with two azole fungicides in female zebrafish
Endocrine disruptors (EDs) can disrupt the gonadotropic axis, which consists of the Hypothalamus-Pituitary-Gonads (HPG), notably by altering aromatase (cyp19a), a key enzyme regulating the endocrine system and reproductive function in fish. The effects of EDs can be predicted by integrating both toxicokinetic (TK) and toxicodynamic (TD) processes in order to relate adverse outcomes to external exposures. In this study, we developed a physiologically based kinetic-toxicodynamic model to simulate the disruption of the HPG axis (PBK-TD, hereafter named PBK-HPG) in female zebrafish exposed to either of two aromatase inhibitors, imazalil or prochloraz. The model was calibrated using Bayesian methods and supported by novel experimental data, including measurements of vitellogenin, 17β-estradiol, and 11-ketotestosterone levels, along with in vivo monitoring of the cyp19a1a gene in transgenic cyp19a1a-GFP ebrafish. Seamless integration of a PBK model within a TD model of the HPG-axis, provided the link between external exposure and internal levels of imazalil and prochloraz in key organs, allowing for mechanistic predictions of their inhibitory effects on gonadal aromatase. Our PBK-HPG model accurately predicted both baseline homeostasis and the effects of aromatase inhibition, with all endocrine endpoints including reproductive disruption, i.e., decreased egg production, falling within a twofold range of both experimental and literature data. Therefore, our PBK-HPG model could further support the development of a mechanistic qAOP with TK considerations. The model offers significant potential for improving environmental risk assessments of EDs and possibly other stressors across species.
(Aquatic Toxicology. vol. 283, n° 0166-445X, pp. 107337, 01/06/2025)
INERIS, SEBIO, INERIS, URCA, ULH, NU, URCA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Seamless nearshore topo-bathymetry reconstruction from lidar scanners: A Proof-of-Concept based on a dedicated field experiment at Duck, NC
Accurate observations of the nearshore bathymetry, including within the breaking wave region, are critical for the prediction of coastal hazards, and improved understanding of sandy beach morphological response to storms. In this paper, we implement the recent Boussinesq theory-based depth inversion methodology of Martins et al. (Geophys. Res. Lett., 50 (2023), Article e2022GL100498) to single-and multibeam lidar datasets collected during a dedicated field experiment on a sandy Atlantic Ocean beach near Duck, North Carolina. Compared with common approaches based on passive remote sensing technology (e.g., optical imagery), lidar scanners present several key advantages, including the capacity to directly measure the beach topography, waveforms and the cross-shore variations in mean water levels due to wave action (e.g., the wave setup), leading to the seamless reconstruction of a vertically-referenced beach topo-bathymetry. Given the potentially gappy nature of lidar data, particular attention is paid to the robust computation of surface elevation spectral and bispectral quantities, which are at the base of the proposed non-linear depth inversion methodology. Promising results on the final topo/bathymetry are obtained under contrasting wave conditions in terms of non-linearity and peak period, with an overall root-mean square error below 0.3 m obtained along a cross-shore transect covering both shoaling and breaking wave conditions. The accuracy of the final bathymetry in the shoaling and outer surf regions is generally found to be excellent, with similar skills as previously obtained in laboratory settings (relative error < 10 -15%). Under the most energetic conditions, an underestimation of the wave phase velocity spectra is observed within the surf zone with all theoretical frameworks, potentially owing to surf zone vortical motions not yet accounted for in the present methodology. This underestimation of the wave phase velocities results in a relatively large overestimation of the mean water depth, between 30% to 100% depending on the theoretical framework. With the methodology described herein, lidars bring new perspectives for seamlessly mapping the nearshore topo/bathymetry, and its temporal evolution across a wide range of scales. Although currently limited to a single cross-shore transect, we believe that opportunities exist to integrate multiple remote sensors, which could address individual sensor limitations, such as coverage (lidar) or the incapacity to directly measure waveforms (optical imagery).
(Coastal Engineering. vol. 199, n° 0378-3839, pp. 104748, 01/06/2025)
LIENSs, INSU - CNRS, ULR, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Distinct toxicity profiles of conventional and biodegradable fishing nets’ leachates after artificial aging
Fishing nets (FNs) represent a significant source of plastic waste, but their contribution to pollution by micro- and nanoplastics (MNPs) and associated additives is poorly understood. We studied the degradation of a highperformance- polyethylene-polypropylene (HPPE-PP) trawl net and two trammel nets made of polyamide 6 (PA6) or biodegradable polybutylene-succinate-polybutyrate-adipate-terephthalate (PBS-PBAT). Accelerated artificial ageing (AA) was performed using UV irradiation under environmental or extreme conditions followed by abrasion in water with glass microbeads. FN degradation and organic compound release were studied as well as the toxicity of leachates on the marine bacteria Allivibrio fischeri and larvae of the fish Oryzias latipes. AA of FNs under environmental conditions caused slight polymer degradation and did not produce significant MNPs. However, under extreme conditions, PA6 and PBS-PBAT FNs produced 9.1 × 104 MP/mL and 2.0 × 104 MP/mL, respectively. FNs released a total of 27 organic compounds in the leachates from which 7 were quantified at concentrations between 0.35 μg/L (Phthalimide) to 200 μg/L (Succinic-acid 2-methylallyl-undecyl-ester). Only the PBS-PBAT FN leachates induced significant toxicity on bacteria, bioluminescence inhibition ranging from26 % to 56 %. Exposure of fish larvae to leachates of AA FNs disrupted their behavior. PBS-PBAT FN leachates caused the highest behavior stress indicator at day 12 (8.5), followed by PA6 at day 25 (8) and HPPE-PP at day 12 (7). We concluded that the toxicity of FN leachates was related more to the release of organic compounds than to the release of MPs. The toxicity of bio-based and biodegradable FNs should be further evaluated before their wider implementation in the fishing sector.
(Journal of Hazardous Materials. vol. 489, n° 0304-3894, pp. 137609, 01/06/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CBMN, UB, ENITAB, INC-CNRS, CNRS
Record of trace organic contaminants in a river sediment core: From historical wastewater management to historical use
(pp. 117, 01/06/2025)
METIS, EPHE, PSL, INSU - CNRS, SU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LEHNA, UCBL, ENTPE, CNRS, GéHCO, UT
Study of aerobic and anaerobic cultivable sedimentary microbiota - Capability of isolates to produce and degrade extracellular polymeric substances and possible use in biotechnology
The thesis is part of a larger project aiming to analyze the Extracellular Polymeric Substances (EPS) contents of sediments from modern and ancient estuaries (ANR “EXODIA”). EXODIA aims to better define the composition and function of EPS in modern and ancient estuaries, and their interaction with clay and metals through diagenesis. The aim of the thesis is to isolate, characterize and identify the culturable microorganisms potentially involved in the estuarine sediment EPS cycle (anaerobic and aerobic bacteria), in particular strains able to produce high quantities of EPS and/or able to degrade EPS. A maximum of microorganisms from the most representative sediment horizons on 6-m deep cores will be isolated by a culturomics strategy relying on the use of 16 media and 2 temperatures of incubation as well as enrichment strategies to focus on EPS degrading and biofilm-forming strains. After isolation and constitution of a strain’s library, each strain will be grown as planktonic and sessile pure culture and their ability to produce EPS (mucoid character), to form biofilms and to produce EPS-modifying enzymes (DNAses, proteases, hydrolases, lyases) will be assayed. Antibiosis and antibiofilm activities of isolates against bacterial reference strains in biofilm research (Escherichia coli and Pseudomonas aeruginosa) will be carried out. All the information relative to the isolates will be listed in a publicly available database. The identification of isolates will be performed in first intention by mass spectrometry. In parallel, genomic identification of the microbiome in sediment samples will be performed. This will allow us to estimate if our isolates are representative of the global community.
(27/05/2025)
CBMN, UB, ENITAB, INC-CNRS, CNRS, ICMCB, UB, INC-CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A karst rather than periglacial origin for small enclosed depressions of the Landes Triangle, southwest France
Small topographic depressions offer insight into past and present groundwater recharge processes. The Landes Triangle (SW France) is dotted with over 2,400 such depressions, whose origins and hydrogeological implications remain unclear. This paper aims to disentangle their origin, with emphasis on the Villagrains-Landiras anticline sector: a key recharge zone, which also features the highest density of depressions. We first evaluate three historical hypotheses with open GIS data at the regional scale, then detail the near-surface structure of a depression near the anticline with electrical resistivity tomographies and ground-penetrating radar. We identify two groups of depressions based on their morphology, distribution and geological context. One aligns with an aeolian origin. The other (encompassing 97% of the depressions near the anticline) suggests a karst origin, with more circular shapes and proximity to karst, streams, faults and neighbouring depressions. However, 18% of these lie outside the crypto-karst area derived from GIS references and may rather be of periglacial origin. Yet, our geophysical survey revealed subsidence but no evidence of cryogenic sediment or solifluction. We conclude that a karst origin remains the best hypothesis in the anticline area, and highlight that sole reliance on GIS references may underestimate crypto-karst extent. Further geological investigation is therefore needed to map its full extent and related water pathways near the anticline.
(Earth Surface Processes and Landforms. vol. 50, n° 0197-9337, 25/05/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ULaval