Three-dimensional numerical modeling of sediment transport in a highly turbid estuary with pronounced seasonal variations
Simulating sediment dynamics in a large and energetic estuary system remains challenging, primarily due to the spatial and temporal complexities of the interaction between flow and sediment transport, especially for sand-mud mixtures. This study uses a three-dimensional (3D) numerical model, based on the open TELEMAC system, to investigate the dynamics of suspended sediment concentration (SSC) in the Gironde Estuary, a complex estuarine environment characterized by an estuarine turbidity maximum (ETM) and significant variations in river discharge. The main contributions of this study include addressing the challenges of coupling bed friction with sediment transport of the sand-mud mixture for feedback on bed roughness and bottom depth changes and the ability of the model to capture the migration of ETM from high to low flow. Additionally, the current study analyzes the ability of the model to capture the migration of ETM from high to low flow, and it utilizes a calibration strategy that minimizes parameters by using in situ data and encompassing hydroemorpho-sedimentary interactions. A sensitivity analysis was done using different settling velocity approaches and sediment classes to establish an optimal model configuration and the uncertainty associated with the reduced model parameterization is discussed. The model satisfactorily reproduces the hydrodynamic features, particularly when the hydro-sedimentary feedbacks are taken into account, the seasonal trend of SSC, springneap variations, and the development of a well-defined ETM. The selection of a specific formulation for the settling velocity influences the location and magnitude of ETM. The van Leussen formula not only predicts a broad movement of ETM from high to low river flow, but also predicts high turbidity for extended periods during low river flow. Conversely, two empirical formulas from Le Hir and Defontaine predicted the highest turbidity during neap tides but sediment losses during prolonged simulations. The results of this study contribute to a deeper understanding of sediment dynamics in the Gironde Estuary, providing valuable information for future estuarine modeling and management.
(International Journal of Sediment Research. vol. 40, n° 1001-6279, pp. 333-347, 01/04/2025)
M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, RHITME, Cerema, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LHSV, EDF R&D, EDF [E.D.F.], ENPC, IP Paris
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
Simulating Shoreline and Nearshore Changes: The LX-ST Model
This paper presents LX-ST, a numerical model that simulates shoreline and nearshore evolution over medium-to long-term timescales across diverse sandy coastal environments. It combines the reduced-complexity shoreline model LX-Shore with the shoreface profile translation tool ShoreTrans, enabling it to capture shoreline changes and 3D nearshore morphology. LX-ST accounts for sea-level rise, sediment transport, complex features like artificial structures (e.g., seawalls, groynes), and natural morphologies (e.g., dunes and barriers). The model is tested on synthetic cases, demonstrating its ability to simulate complex coastal configurations. It is then applied to a 5-km beach-dune system in southwest France, which includes a 1.2-km-long seawall. Results show good agreement with observed past shoreline changes and reveal how LX-ST can predict future coastal trajectory shifts, including the eventual retreat and potential disappearance of the beach fronting the seawall. These findings underscore the model's utility in forecasting shoreline
(25/03/2025)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BW-CGC
Tide-dominated estuaries as gateways and filters of plastic pollution to the Ocean: insights from the PLASTINEST project
Around three-quarters of oceanic plastic waste come from land-based sources and is mainly transported via rivers and estuaries. However, not all plastics entering estuarine environments reach the open Ocean. Plastic litter and particularly microplastics, can accumulate in estuaries, creating pollution hotspots. This retention may be especially pronounced in macrotidal estuaries, where strong landward residual flows enhance trapping. The ANR PLASTINEST project aims to advance our understanding of the transport, trapping, and dispersion of microplastics within estuarine environments dominated by tides. Using innovative field measurements, controlled physical experiments, and enhanced numerical modeling, PLASTINEST offers new insights into the physical processes that govern particle transport under varying environmental conditions. Ultimately, this research contributes to the ongoing scientific debate on the assessment of plastic river input to the ocean and the existence of a “missing ocean plastic sink”, which to this day ignores the potential trapping role of tide-dominated estuaries. In this work, we present the methodology and key results of PLASTINEST, through three work packages:In the first work package, laboratory experiments provided insights into the erodibility, bottom trapping, and settling dynamics of microplastics in the presence of muddy sediments characteristic of estuarine environments. Both, bottom resuspension and settling behavior were primarily influenced by particles physical properties—shape, density, and size. The presence of cohesive sediment has a secondary influence on microplastics transport in turbid estuaries by increasing the critical shear stress of microplastics deposited on the bed and by promoting flocculation in the water column. These two processes favor the retention and accumulation of particles in turbid estuaries.In work package 2, the spatio-temporal variability of microplastics is evaluated across a macrotidal estuary, in relation to key physico-chemical parameters, through ongoing field campaigns. A novel protocol for sampling microplastics has been implemented in the Gironde estuary, using an innovative in-situ filtration system. Data post-processing will elucidate on the role of hydrodynamics (tides, river discharge, longitudinal tidal and salinity gradient, vertical mixing) on microplastic concentration variability and distribution patterns within the estuary.Numerical modelling tools for the transport of plastic debris were improved to include key microplastic transport processes in work package 3. The implementation of these in the Gironde Estuary provided key insights on the role of environmental factors and transport mechanisms on the trapping and dispersion patterns of microplastics across different temporal scales (from intratidal to seasonal) for floating and sinking particles. Beaching, convergent currents and tidal pumping were identified as key trapping mechanism retaining particles inside the estuary. Interestingly, during wet period, the high river discharge flushes important amount of floating particles into the Ocean , while settling particles remain in the estuary.By synthesizing insights from earlier findings, PLASTINEST will provide a comprehensive view of how plastic particles are transported, accumulate, and are periodically exported to the Ocean within tide-dominated estuarine systems.
(25/03/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UAS, RHITME, Cerema, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, SIAME, UPPA, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, HydEE, Département FTC, PPrime [Poitiers], UP, ISAE-ENSMA, CNRS, UP, Cerema Direction Est, Cerema, CBMN, UB, ENITAB, INC-CNRS, CNRS
How scientific networks can help advancing both scientific knowledge and public policies: the case study of the “Plastics, Environment and Health” network
The “Plastics, Environment and Health” research network (groupement de recherche, GDR) created in 2019 gathers the French scientific community working on plastic pollution in all environments (soil, air, water) and their impact on ecosystems and human health. The scientific objective is to rapidly increase knowledge on plastic pollution by supporting collaboration of researchers from different fields such as ecotoxicology, chemistry, physics, microbiology, oceanography and social science. Research is carried out at each stage of the plastic life cycle, (from resource extraction all the way to removal and remediation) and across the entire air-soil-water continuum, integrating transfers of both plastic particles (macro, micro- and nanoplastics) and plastic chemicals (e.g., additives) between different environmental compartments. In this context, the GDR supports the development of multi-scale and transdisciplinary approaches across three main axes: Axis 1 - Air-soil-water continuum: contamination levels and transfer between compartments; Axis 2 - Interactions and transformation of plastics in environmental compartments and living organisms; Axis 3. Plastic pollution risk assessment for ecosystems and human health. To do so, the GDR’s actions focus on (1) training and sharing of scientific knowledge, including developments towards innovation, (2) support for collaboration and interdisciplinarity between network members, (3) dissemination, structuring of the community and its national and international influence, and (4) support for public policy and/or decision-making by strengthening the link between scientists, decision-makers and the plastic industry. To date the research network includes more than 50 laboratories spread across France and over 300 scientists in the field of physics, chemistry, biology, ecology and social sciences. Such a network constitutes a powerful tool to build robust science-based knowledge significantly contributing to the international effort, to disseminate state-of-the-art scientific advances and research priorities needed to tackle plastic pollution to Society and to inform policy makers. This talk will present the French taskforce addressing 'Plastic, Environment, and Health' within the national research network, where the entire community works collaboratively to tackle the urgent challenges of plastic pollution, its environmental consequences, and the associated risks to human health. We will also discuss the importance of building a French-speaking community to support multilingualism in international political science interactions.
(25/03/2025)
LEMAR, IRD, IFREMER, UBO EPE, CNRS, IPREM, UPPA, INC-CNRS, CNRS, MMV, L2C, CNRS, UM, LSAl, ANSES, iEES Paris, IRD, SU, UPEC UP12, CNRS, INRAE, GERS-LEE, ToxAlim, ENVT, Toulouse INP, Comue de Toulouse, Toulouse INP, Comue de Toulouse, INRAE, EPE UT, Comue de Toulouse, EI Purpan, Comue de Toulouse, LOMIC, INSU - CNRS, SU, CNRS, OOB, SU, CNRS, Softmat, INC-CNRS, CNRS, EPE UT, Comue de Toulouse, ICT, IRD, INC-CNRS, CNRS, Toulouse INP, Comue de Toulouse, EPE UT, Comue de Toulouse, IMMM, UM, INC-CNRS, CNRS, IRDL, ENIB, UBO EPE, Bretagne INP, UBS, UBO EPE, CNRS, ENSTA, IP Paris, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR MARBEC, IRD, IFREMER, CNRS, UM
Gloves Standards and Occupational Exposure to Antineoplastic Drugs in the European Context
ABSTRACT Background and Aims Over 12 million healthcare professionals in Europe are exposed to hazardous medicinal products, including antineoplastic drugs. Dermal route is recognized as the primary route of exposure to antineoplastic drugs, emphasizing the critical importance of skin protection provided by gloves, which necessitates a careful and specific selection process. This study aims to compare the current European standard EN 16523‐1:2015 + A1:2018 with the ASTM D6978‐05(2023) standard used in the United States. Methods Firstly, the three main performance parameters to consider when selecting gloves are described: standardized breakthrough time, standardized permeation rate, and cumulative permeation. Subsequently, the current European and American standards are compared based on the following criteria: part of the glove tested, substances tested, standardized permeation rate, test duration, test temperature, and the information provided on the glove packaging. Additionally, and with a focus on safety, clear examples of how to interpret graphical symbols and indications available on glove packaging are provided to enhance the transferability of the information contained in this study to healthcare settings. Results There is a significant disparity between the requirements of the two standards. Indeed, the only European standard applicable in the context of glove permeation by antineoplastic drugs requires a standardized permeation rate 100 times less stringent than the American standard and does not include any hazardous drugs in its list of substances to be tested. By proposing a list of 24 antineoplastic drugs to be tested, a test temperature of 35 ± 2°C (compared with 23 ± 1°C in the European standard), and by specifically targeting the thinnest part of the glove, the American standard is closer to real‐world conditions of use compared to its European counterpart. Conclusion This study underscores the limitations of current European standard, advocating for regulatory updates to better protect healthcare professionals, while emphasizing the complexity of selecting appropriate gloves for antineoplastic and hazardous drug exposure. Clinical Trial Registration Not concerned.
(Health Science Reports. vol. 8, n° 2398-8835, 24/03/2025)
IRSET-ESTER, Irset, UA, UR, EHESP, INSERM, Biosit : Biologie - Santé - Innovation Technologique, BPH, UB, INSERM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
A Common Terminology to Unify Research and Conservation of Coralline Algae and the Habitats They Create
Linguistic uncertainty is a prime source of uncertainty pervading ecology and conservation. Coralline algae are a widespread and diverse group of calcifying red macroalgae that underpin coastal ecosystem function and service provision. Recent increasing interest in coralline algae in the scientific literature has revealed a diverse but confusing terminology at organism to habitat scales. Coralline algal research and conservation are international and multidisciplinary, so there are geographic and disciplinary imbalances in research and conservation efforts. To reach consensus and reduce uncertainty, we propose a unified terminology. We review trends in cultural and scientific use of coralline algal terms and propose a system based on six morphologies: (1) attached, (2) free‐living geniculate, (3) encrusting and free‐living nongeniculate coralline algae, the latter either being (4) nucleated or (5) non‐nucleated thalli or (6) fragments. We take inspiration from other coastal systems that have achieved consensus through umbrella terms, such as ‘coral’ and ‘kelp’, to accelerate global progress in coralline algal research and conservation. We characterise 14 coralline algae–dominated habitat global types, falling within seven functional groups, four biomes and four realms: (1) freshwater coralline streams; (2) coralline tide pools; (3) intertidal coralline rims and (4) turf; (5) coralline sea caves; (6) coral–algal reefs; (7) algal ridges; (8) coralligenous reefs; subtidal (9) carbonate crusts, (10) coralline barrens and (11) turf; and (12) articulith, (13) maerl and (14) rhodolith beds, which fall into the coralline algal bed functional group. We hope this unified terminology promotes data comparison, enables cross‐boundary and cross‐sector sharing of best practices, develops capacity for meta‐analyses and improves conservation strategies.
(Aquatic Conservation: Marine and Freshwater Ecosystems. vol. 35, n° 1052-7613, 24/03/2025)
LEMAR, IRD, IFREMER, UBO EPE, CNRS, UFRJ, IUEM, IRD, INSU - CNRS, UBO EPE, CNRS, DYNECO, IFREMER, UGR, NHM, CDPQ, INTECHMER, Cnam, LUSAC, UNICAEN, NU, IMR, UiB, UDC, UAlg, FIOCRUZ, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Plant Community Responses to Climate Change: The Importance of Ecological Context Dependencies
(Journal of Vegetation Science. vol. 36, n° 1100-9233, 21/03/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IB / CAS, CAS, EDYSAN, UPJV, CNRS
Records of vegetation and South Asian summer monsoon dynamics in the Bay of Bengal during the current and last interglacial periods
While it is accepted that the tropical hydrological cycle has intensified during past interglacial periods due to changes in insolation, greenhouse gases, and ice volume, variations in the intensity and spatial distribution of rainfall in the South Asian monsoon domain, as well as the respective influence of these forcings during past warm periods, remain uncertain. Here, we present a pollen record from the Bay of Bengal (IODP Site U1446, located off the Mahanadi river exit, outside the influence of the Bengal fan) that allows reconstruction of vegetation changes in the core monsoon zone of India during two warm periods, the current and last interglacial periods. We compare the data with numerical model simulations (HadCM3 and LOVECLIM1.3) to assess the influence of different forcing mechanisms on the response of summer monsoon rainfall during past interglacials characterized by different levels of warming (Clément et al., 2024). We also present a pollen record from cores (SO93) taken at 16°N from the Ganges-Brahmaputra-Meghna (G-B-M) river-fed Bengal fan, covering the current interglacial period.Results from IODP Site U1446 show tropical forest expansion between 11.7-5 ka and 127-120 ka, defining two Indian humid periods, with the last interglacial showing the strongest monsoon activity, consistent with salinity reconstructions. During the last five millennia of both interglacial periods, moist tropical forest largely declined in favor of savanna marking a significant decrease in summer monsoon rainfall. Although the pollen assemblages from sites SO93 and U1446 show substantial differences in Holocene vegetation cover between the basins, the maximum expansion of the evergreen component of the tropical forest is recorded contemporaneously in both sequences. This suggests a similar Holocene evolution of the summer monsoon from central to northern India. The model-data comparison highlights boreal summer insolation as the primary driver of vegetation dynamics and monsoon intensity during interglacial periods, with CO2 and ice-sheets having a limited effect. These results also show that vegetation remains unaffected by pre-industrial CO2 variations above 250 ppmv, a threshold value that characterizes most interglacials of the last million years.Clément, C., Martinez, P., Yin, Q., Clemens, S., Thirumalai, K., Prasad, S., Anupama, K., Su, Q., Lyu, A., Grémare, A., Desprat, S., 2024. Greening of India and revival of the South Asian summer monsoon in a warmer world. Commun. Earth Environ. 5, 685.
(pp. 9895, 18/03/2025)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ELI, UCLouvain, UL, CRPG, INSU - CNRS, UL, CNRS, IFP, MEAE, CNRS, UCLouvain, Bordeaux INP, WHOI