Modelling Microplastic Dynamics in Estuaries: A Comprehensive Review, Challenges and Recommendations
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
Regional assessment using public webcams of the role of post-storm recovery in the seasonal variability of beach width
Understanding the mechanisms and times required for beaches to recover after extreme storms, as well as the effect of these episodic setbacks on long-term coastal erosion trends, is crucial for anticipating changes and implementing effective management strategies. A storm can have significant impacts on the coastline, resulting in retreats of several meters within hours. The natural recovery of the beach in the hours/days following a storm varies greatly between sites, ranging from a few days to several months. In this study, we examine the regional variability in coastal response during winter storms and post-storm recovery, using a beach width indicator obtained through the analysis of public webcam images on event, seasonal, and multi-year time scales. Video-derived shoreline positions were used to calculate weekly average beach widths at 11 sites along the coastline of Occitanie. The analysis demonstrated that storm responses and seasonal trends exhibit significant variability despite similarities in morphologies, and exposure to storm waves. Although post-storm recovery following the major events of 2021 and 2022 was nearly complete and very rapid for most sites, some beaches experienced prolonged recovery periods, requiring several months to return to their initial position. While the results indicated that storm events were sufficiently spaced to allow these beaches to recover, a series of events in autumn 2023 raises questions about this recovery capacity and underscores the potential impact of singular events on medium- and long-term coastal evolution trends.
(. vol. 2, 07/04/2025)
BRGM, UniFE, UM, 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 SHORELINE DYNAMICS IN COMPLEX MACROTIDAL ENVIRONMENTS USING NEURAL NETWORKS
The aim of this work is to test an artificial intelligence approach with basic hydrodynamic and morphological variables, in order to assess the effectiveness of such methods in modelling complex beach dynamics. A simple feedforward neural network is used to evaluate the impact of selected variables on the prediction of the dynamics of specific shoreline isocontour proxies extracted from beach profiles, and to build a predictive model that could simulate the position of the proxies. The model was trained on datasets from two sites from the French coastal monitoring program DYNALIT, Porsmilin and Vougot beaches, and their profile measurements, water levels and wave measurements over 20 years. These two sites were selected due to differences in their morphology and hydrodynamics, as a means to assess the performance of neural networks over a larger variety of situations. A range of temporalities encompassing 3 days, 7 days, 14 days, and 30 days of selected hydrodynamic and morphological variables were used to study the impact time scales can have on modelled shoreline positions. The shoreline proxies used for Porsmilin and Vougot beaches correspond respectively to the berm and the contact between the dune toe and the upper beach, which can be assessed and followed along each beach profile. The shallow feedforward network included 1 hidden layer and 5 nodes, and was ran 50 times in order to assess the models' performance. The models were generally successful, with a blind shoreline prediction R of 0.88 in Porsmilin and 0.72 in Vougot. This artificial neural network (ANN) approach showed all-around better performance than previous beach equilibrium models, which is very encouraging regarding the prediction of future beach morphodynamics and the use of Machine Learning algorithms therein.
(07/04/2025)
UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS, LGO, UBS, IFREMER, UBO EPE, CNRS, LETG - Brest, UBO EPE, UR2, CNRS, LETG, UBO EPE, UR2, CNRS, Nantes Univ - IGARUN, LHSV, EDF R&D, EDF [E.D.F.], ENPC, IP Paris
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
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
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
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
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