Use of solute concentration gradients in the benthic boundary layer to highlight sediment source-sink dynamics: a non-invasive \textitin situ study
Oxygen, nutrients, and pollutants fluxes at the sediment-water interface are involved in the water quality and ecological status of shallow coastal environments. The short-term variabilities of these fluxes, in response to hydrodynamic and benthic biogeochemical processes in the field, make it difficult to assess the net balance of these fluxes. Here we evaluate the ability of using concentration gradients in the benthic boundary layer to better understand temporal variations in these fluxes. Three shallow Mediterranean coastal lagoons (Berre, Thau and Prévost lagoons), affected by deoxygenation events and depicting contrasting water quality status, were investigated. A Benthic Oxygen Gradient Observatory System (BOGOS) was set-up and deployed for two weeks in each lagoon to obtain continuous oxygen gradient time-series. In addition, concentration gradients of nutrients (Si, NH4+, PO43−) and trace elements (Fe, Mn, Co, As, Cu, Mo, MeHg) were obtained using a specifically dedicated benthic water sampler (SUSANE) deployed under contrasting oxygenation conditions (oxic, hypoxic, anoxic, euxinic) and diurnal cycles (day and night). The results enabled us firstly to better define the limits of applying the gradient method in shallow coastal areas, considering environmental conditions (water stratification, intense water mixing, low flux intensity) as well as technical limitations (concentration uncertainty). This approach then allowed to accurately capture contrasted benthic oxygen dynamics: diurnal cycles in sediments colonized by macrophytes in Prévost and Thau lagoons, and a dominant high oxygen demand in bare sediments in Berre lagoon. Benthic solute gradients in Berre lagoon indicated release of nutrients from the sediment under normoxic conditions after a long-term anoxic event, as well as release of dissolved Mn, Fe, As and Co under anoxic conditions. Under euxinic conditions, gradients reversed for most trace elements that were trapped in sediment due to (co)precipitation with sulfide minerals, while nutrient gradients indicated continuing sizeable releases to the water column. The benthic concentration gradient approach can thus be seen as a promising approach in assessing the dynamics of benthic fluxes at an appropriate time scale in highly dynamic shallow coastal lagoons. This effort should be completed by vertical turbulent diffusivity measurements, to obtain time series of turbulent fluxes of various solutes.
(Estuarine, Coastal and Shelf Science. vol. 323, n° 0272-7714, pp. 109432, 24/05/2026)
CHROME, UNIMES, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UAG, INSU - CNRS, UM, CNRS, CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE, UMR Marbec - Station Sète, UMR MARBEC, IRD, IFREMER, CNRS, UM, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, LCE, AMU, INC-CNRS, CNRS, HSM, IRD, INSU - CNRS, CNRS, UM, CCEM, IFREMER
Geomorphological evolution in a medium macrotidal estuary across 88 years: shift from natural to human-influenced states
Since the 1970s, human activities such as navigational projects, land reclamations, sand mining, and upstream damming have significantly impacted the geomorphology of Oujiang River Estuary (ORE). This study utilized bathymetric surveys, river discharge data, tide records, historical current velocity and suspended sediment concentration, and historical satellite imagery to investigate the geomorphological evolution of ORE over the past 88 years. The results reveal a distinctive five-phase evolution: a period of pronounced erosion (1931-1964), followed by pronounced deposition (1964-1979), minor erosion/deposition fluctuations (1979-2007), rapid erosion (2007-2014) and fast back-siltation (2014-2018). In its natural state before the 1970s, the ORE exhibited 2 morphodynamics characterized by wandering, braided, and meandering channels interspersed with shoals. Meanwhile, its erosion and deposition pattern featured a dynamic equilibrium: high river discharge induced erosion, while dominant flood tides facilitated net upward sediment transport and deposition during low river discharge. However, post-1970s human activities disrupted this natural equilibrium and led to various geomorphological responses. Navigational projects stabilized shoals and channels, affecting local sedimentation. Dams reduced the frequency and peak of floods, thus reducing the potential for erosion. Land reclamations narrowed channels and reshaped the coastline. Sand mining and dredging for reclamation contributed significantly to erosion, especially during 1979-2014. The Empirical Orthogonal Function analysis revealed two primary morphodynamic patterns. The first mode indicates long-term continuous erosion in the channel and siltation over the tidal flat, identifying navigational projects and sand mining as the dominant causes of the main morphological changes. The second mode describes the transition from erosion to siltation, highlighting land reclamations and reservoir dams as the key factors driving this transition. Furthermore, human activities changed hydrodynamics and sediment transport, likely enhancing tidal pumping and strengthening longitudinal circulation. Consequently, the net up-estuary sediment transport had been intensified, ultimately resulting in fast back-siltation during 2014-2018. This insight is essential for sustainably managing medium-sized macrotidal estuaries, especially as they shift from natural to human-influenced states.
(Journal of Hydrology. vol. 655, n° 0022-1694, pp. 132933, 24/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Modeling the potential source routes of marine macroplastics on a beach adjacent to the Patos Lagoon Estuary, South Brazil
Cassino Beach, on the southernmost coast of Brazil, is especially vulnerable to plastic pollution due to its 220 km-long coastline and proximity to the Patos Lagoon Estuary, which is influenced by urbanization, industrial activities, and intense coastal fishing. This study investigates the aquatic origin (lagoon or ocean) of stranded macroplastics during the summer and winter of 2016 at two sites: one located 3-5 km from the estuary mouth and another approximately 40 km away. A backward particle tracking approach was applied, combining the TELEMAC-3D hydrodynamic model with the TrackMPD model. Model validation using a buoy experiment showed a maximum difference of less than 500 m between real and virtual particle trajectories. A total of 100 virtual particles (0.8 m LDPE sheets, ρ = 0.94 g•cm⁻³) were released per site and season. At the near-estuary site (S1), most particles (75% in summer, 68% in winter) originated from the central region of Patos Lagoon, while an additional 6% (summer) to 25% (winter) came from the São Gonçalo Channel. At the remote site (S4), particles mainly originated from marine regions: 98% (winter) and 43% (summer: 30% SW + 13% NE coastal domain) Simulated transport times ranged from 4.7 to 83 days, with shorter durations during winter due to stronger coastal currents. These results highlight the dominant role of estuarine outflow in transporting macroplastics to areas near the Patos Lagoon mouth, whereas remote areas are influenced by long-distance marine transport, particularly from fishing zones. The integration of numerical modeling with field data is the main contribution of this study to improve our understanding of debris sources and support more effective management strategies.
(Marine Pollution Bulletin. vol. 220, n° 0025-326X, pp. 118349, 24/05/2026)
FURG, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EABX, INRAE
Machine Learning Beach Attendance Forecast Modelling from Automatic Video-Derived Counting
Accurate predictions of beach user numbers are important for coastal management, resource allocation, and minimising safety risks, especially when considering surf-zone hazards. The present work applies an XGBoost model to predict beach attendance from automatically video-derived data, incorporating input variables such as weather, waves, tide, and time (e.g., day hour, weekday). This approach is applied to data collected from Biscarrosse Beach during the summer of 2023, where beach attendance varied significantly (from 0 to 2031 individuals). Results indicate that the optimal XGBoost model achieved high predictive accuracy, with a coefficient of determination (R2) of 0.97 and an RMSE of 70.4 users, using daily mean weather data, tide and time as input variables, i.e., disregarding wave data. The model skilfully captures both day-to-day and hourly variability in attendance, with time of day (hour) and daily mean air temperature being the most influential variables. An XGBoost model using only daily mean temperature and hour of the day even shows good predictive accuracy (R2 = 0.90). The study emphasises the importance of daily mean weather data over instantaneous measurements, as beach users tend to plan visits based on forecasts. This model offers reliable, computationally inexpensive, and high-frequency (e.g., every 10 min) beach user predictions which, combined with existing surf-zone hazard forecast models, can be used to anticipate life risk at the beach.
(Journal of Marine Science and Engineering. vol. 13, n° 2077-1312, pp. 1181, 24/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR ETTIS, INRAE, UR EABX, INRAE, EPOC, SMGBL
New records of the jellyfish Rhizostoma luteum (Scyphozoa: Rhizostomeae) in the Bay of Biscay, and update of its distribution area
The authors report new observations of the giant jellyfish Rhizostoma luteum based on field observations and photographic databases from citizen sciences from 2017 to 2023. These observations indicate the presence of this species in the south of the Bay of Biscay, where it has been observed on several occasions and at different locations, suggesting a regular presence in the area. These observations represent the most northerly reports for the North-East Atlantic and the first on the French coast. An update of its distribution has highlighted the presence of the species as far south as South Africa in the South-East Atlantic.
(Cahiers de Biologie Marine. vol. 66, n° 0007-9723, pp. 5-9, 24/05/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LERAR, COAST, IFREMER, IRSTEA, LERPAC, COAST, IFREMER
Main conclusions and perspectives from the collective scientific assessment of the effects of plant protection products on biodiversity and ecosystem services along the land–sea continuum in France and French overseas territories
Preservation of biodiversity and ecosystem services is critical for sustainable development and human well-being. However, an unprecedented erosion of biodiversity is observed and the use of plant protection products (PPP) has been identified as one of its main causes. In this context, at the request of the French Ministries responsible for the Environment, for Agriculture and for Research, a panel of 46 scientific experts ran a nearly 2-year-long (2020-2022) collective scientific assessment (CSA) of international scientific knowledge relating to the impacts of PPP on biodiversity and ecosystem services. The scope of this CSA covered the terrestrial, atmospheric, freshwater, and marine environments (with the exception of groundwater) in their continuity from the site of PPP application to the ocean, in France and French overseas territories, based on international knowledge produced on or transposable to this type of context (climate, PPP used, biodiversity present, etc.). Here, we provide a brief summary of the CSA's main conclusions, which were drawn from about 4500 international publications. Our analysis finds that PPP contaminate all environmental matrices, including biota, and cause direct and indirect ecotoxicological effects that unequivocally contribute to the decline of certain biological groups and alter certain ecosystem functions and services. Levers for action to limit PPP-driven pollution and effects on environmental compartments include local measures from plot to landscape scales and regulatory improvements. However, there are still significant gaps in knowledge regarding environmental contamination by PPPs and its effect on biodiversity and ecosystem functions and services. Perspectives and research needs are proposed to address these gaps.
(Environmental Science and Pollution Research. vol. 32, n° 0944-1344, pp. 2757–2772, 24/05/2026)
RiverLy, INRAE, ECOSYS, INRAE, IFREMER, ISA, UNS, CNRS, INRAE, UniCA, LMGE, CNRS, UCA, UMR BAGAP, ESA, INRAE, Institut Agro, LPED, IRD, AMU, INERIS, EMMAH, AU, INRAE, VAS, ICE, VAS, CRIOBE, UPVD, EPHE, PSL, CNRS, SEBIO, INERIS, URCA, ULH, NU, URCA, CNRS, CNELIAS, AU, AMU, MMSH, AMU, CNRS, CNRS, LBBE, UCBL, VAS, CNRS, LBBE, UCBL, VAS, CNRS, INRAE, Institut Agro, UBE, LCE, CNRS, UMLP, UBFC, UMR SAVE, UB, Bordeaux Sciences Agro, INRAE, DECOD, IFREMER, INRAE, Institut Agro, Institut Agro, OFB Service Santé Agri, OFB - DRAS, OFB, GREDEG, UNS, CNRS, UniCA, ENSFEA, LEREPS, UT Capitole, Comue de Toulouse, UT2J, Comue de Toulouse, ENSFEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR Eco&Sols, Cirad, IRD, INRAE, Institut Agro, IODE, UR, CNRS, UPR HORTSYS, Cirad, Cirad-PERSYST, Cirad, UMR MARBEC, IRD, IFREMER, CNRS, UM, AMURE, IRD, IFREMER, UBO EPE, CNRS, UR EABX, INRAE, IMBE, AU, AMU, CNRS, UdG, PHYTOX, IFREMER, CUFR, URAFPA, UL, INRAE, UR HYCAR, INRAE, DEPE, INRAE
Biological features for a minimum conservation reference size revision – case of Ruditapes philippinarum in Arcachon Bay (French Atlantic coast)
The Minimum Conservation Reference Size (MCRS) for marine resources ensure that individuals can mature and reproduce at least once before being caught. For management purposes, MCRS should be revised for specific populations in given areas. In Arcachon Bay (southwest France), fishers have repeatedly requested a review of the MCRS for R. philippinarum. In 2020, a joint recommendation, supported by France, was addressed to the European Commission suggesting a possible reduction in the MCRS of R. philippinarum from 35 mm to 32 mm for Arcachon Bay. This paper provides an overview of the biological features that need to be considered to support such a review, primarily focusing on sexual maturity, individual growth and natural mortality. The reproductive cycle and size at first maturity, estimated at 26.7 mm for the Bay, were found to be similar to other locations in France and in Portugal. The greatest length at which growth slowdown occurred ranges between 24.0 and 31.5 mm with few differences among sites and no significant differences within each site (at hypsometric levels). The natural mortality coefficients were high with 0.67 yr−1 and 0.51 yr−1 for juveniles and adults, respectively. Regarding productivity (resulting from growth and mortality processes) and all methods combined, the optimal balance between individual growth and natural mortality above 30 mm was found at a mean length of 32.2 mm for the intra-lagoon sites and at a mean length of 36.8 mm for the oceanic sites. Based on available information, reducing the MCRS to 32 mm would not threaten population viability. However, the European Commission has raised warning points, which are discussed in light of current regulations in Arcachon Bay.
(Estuarine, Coastal and Shelf Science. vol. 320, n° 0272-7714, pp. 109288, 24/05/2026)
LMAP, UPPA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Projet IMPEC : IMpact de la PEChe sur les écosystèmes benthiques du large - Evaluation des habitats benthiques du circalittoral du large dans le golfe du Lion au regard des pressions issues des activités de la pêche démersale aux arts traînants : approche multi-indicateurs - Note de synthèse
Ce projet s'inscrit dans le cadre de l'acquisition de connaissance nécessaire au développement et à la consolidation d'indicateurs DCSMM permettant de qualifier l’intégrité des fonds face aux pressions anthropiques sur le plateau continental. Parmi les indicateurs appliqués actuellement pour quantifier le pourcentage de surface impactée et plus précisément l’intensité de l’impact, aucun n’a été spécifiquement développé et/ou testé sur une perturbation physique telle que celle résultant des pêcheries démersales. Or, la pêche aux arts traînants (chaluts et dragues) est la source de perturbation majeure des fonds sur le plateau continental (e.g. Amoroso et al., 2018 ; Brivois et al., 2018 ; Jac et al., 2020). Cette tâche est rendue d’autant plus difficile qu’il est complexe de qualifier des états de référence, au sens « non-impacté » par les pressions d’origine anthropique. Le projet IMPEC propose d’étudier l’impact de la pêche aux arts traînants sur les fonds marins du plateau continental du golfe du Lion en Méditerranée. Le but du projet est de tester plusieurs indicateurs applicables à différentes composantes benthiques (méga-épifaune, macrofaune, méiofaune, foraminifères) pour évaluer l’état des habitats benthiques meubles au regard de l’impact de la pêche de type dragage et chalutage le long d’un gradient de pression d’abrasion.
(pp. 25, 24/05/2026)
LPG-ANGERS, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, LECOB, SU, CNRS, OOB, SU, CNRS, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, Nantes Univ, BIAF, UA, NOC, LPTC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR MARBEC, IRD, IFREMER, CNRS, UM
Assessment of Beach Slope and Sediment Grain Size Anywhere in the World: Review of Existing Formulae, Integration of Tidal Influence, and Perspectives from Satellite Observations
Grain size and beach slope are critical factors in coastal science and management. However, it is difficult to have information on their distribution everywhere in the world, as most of the coast has never been documented. For many applications, it is essential to have at least a rough estimate when local field measurements are not available. Here, we review the existing prediction formulas relating beach slope to grain size and wave conditions, using publicly available global datasets and comparing them with a benchmark dataset of ground measurements from different authors worldwide. Uncertainties arise from the input parameters, in particular coastal waves, a key parameter of all formulae, but also from empirical coefficients that are undocumented or inaccessible with the global dataset. Despite the recognized importance of tides, they are often overlooked in formulae relating beach slope to sediment grain size. We therefore present an improved formulation that incorporates tidal effects. Although satellites offer a promising alternative to predictive formulae for direct estimation of beach slope and grain size, the current accuracy and methodologies of satellite data are insufficient for global applications. Continued advances in satellite missions, including higher resolution and revisit frequency, as well as new sensors, are essential to improve predictive capabilities and facilitate wider implementation.
(Journal of Marine Science and Engineering. vol. 13, n° 2077-1312, pp. 58, 31/12/2024)
LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, Comue de Toulouse, IRD, UT3, Comue de Toulouse, CNES, CNRS, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SHOM
Study of intense pulsed light as a new remediation process for pesticides in water using mass spectrometry and ecotoxicological approaches
Pulsed light (PL) technology was investigated as a pesticide removal process. The degradation of 20 pesticides in water was monitored by mass spectrometry and revealed 74 photoproducts. Structure hypotheses were proposed for 47 photoproducts according to their fragmentation, isotopic pattern, and literature data. This work enabled the development of a LC-MS method for the relative quantification of photoproducts and for the absolute quantification of their parent pesticides.
This analytical method was then applied in optimizing the PL parameters. It was demonstrated that increasing voltage and fluence leads to more efficient pesticide degradation, with concentration reduction of 99 % for 14 pesticides. The compound sensitivity seems to be family dependent. Moreover, PL succeeded in degrading the photoproducts themselves.
Acute toxicity tests were performed on the bacteria Aliivibrio fischeri. A significant reduction in toxicity was observed for 10 out of 18 individual pesticides, while no increase was observed for the remaining seven. When applied to a cocktail solution, the toxicity decreased by 7.25-fold between the untreated and the most PL treated solution. This work demonstrates that PL is a promising process for removing pesticides from contaminated water. Further studies are needed to demonstrate the safety of treated wastewater on various trophic links.
(Journal of Hazardous Materials Advances. vol. 17, n° 2772-4166, pp. 100577, 26/12/2024)
OENO, UB, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS