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, 21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LERAR, COAST, IFREMER, IRSTEA, LERPAC, COAST, 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, 21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
History of the Sedimentary Regimes of the Aquitaine Margin (Bay of Biscay, France) at the Outlet of its Main Tributaries During the Last Millennium: A Mirror of the North Atlantic and European Climates
(21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEO-OCEAN, UBS, IFREMER, INSU - CNRS, UBO EPE, CNRS
Manila clam (Ruditapes philippinarum) in France: Fishing activity, governance and present knowledge challenges regarding its biology and ecology
Originally introduced to France in the 1970s for aquaculture purposes, the clam Ruditapes philippinarum (Adam and Reeve, 1850) has thrived in favourable conditions across numerous sites along the Bay of Biscay, English Channel and Mediterranean coasts forming neo-naturalized populations. It is harvested by both recreational and professional fishers, with an estimated production ratio of 2.4 for both activities combined. Total French commercial fishing production is roughly estimated at around 2000 to 3000 tons per year. This activity is managed by three types of regulation at different scales: European (Minimum Conservation Reference Size - MCRS), national (licenses), and regional. Regional instruments govern fishing practices by setting spatial and temporal access rules to fishing grounds (also referred to as deposits), prohibiting certain gear types at the local scale, determining the minimum size of clam fishing (above MCRS) and setting fishing quotas. Not all of them are implemented everywhere; most often, they are based on stock assessment results and specific research programs, which are not available in every location. This article first provides a review of available information on current Manila clam production in France, and its regulation. Second, it offers an overview of recent knowledge mobilized for management purposes. This overview covers biological and ecological processes (i.e. population dynamics, reproduction and spawning, habitats considerations, biotic interactions and infectious diseases), and enables us to identify future research prospects of interest.
(Estuarine, Coastal and Shelf Science. vol. 317, n° 0272-7714, pp. 109206, 21/02/2026)
LERAR, COAST, IFREMER, LMAP, UPPA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR MARBEC, IRD, IFREMER, CNRS, UM, ASIM, IFREMER, DECOD, IFREMER, INRAE, Institut Agro, Institut Agro, SBR, SU, CNRS, AD2M, CNRS, SBR, SU, CNRS, LOV, INSU - CNRS, SU, CNRS, IMEV, INSU - CNRS, SU, CNRS, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, SMEL, LEMAR, IRD, IFREMER, UBO EPE, CNRS, UR ETTIS, INRAE
Wave Input-Reduction for Shoreline Modelling of a High-Energy Environment with Complex Geological Settings
The long-term (decades) evolution of shoreline change along coastline (O(15)Km) with complex offshore wave transformation challenges both, state of the art process-based morphodynamics and reduce-complexity shoreline models. A major limitation is the computational time required to simulate the detailed spatiotemporal evolution of the wave field, particularly in regions where offshore wave refraction induces localized energy focusing. This study focuses on a 15-Km sandy coast on the North Medoc, southwestern France, characterized by high-energy, macro-tidal conditions, severe erosion, and complex offshore bathymetry. Effective coastal management strategies for the coming decades require the implementation of a reduced-complexity (RC) shoreline model. However, oversimplification of wave transformations in such a complex hydro-morphodynamic environment can result in flawed predictions of alongshore wavebreaking parameters and, consequently, shoreline change. Thus, a full wave propagation model is required, but computational time reduction techniques must be implemented to minimize computational cost. To address these challenges, this study introduces an easy-to-apply input reduction (IR) methodology that integrates offshore wave clustering to reduce computational costs when modeling long-term shoreline change within RC shoreline models.
(21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
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, 21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR ETTIS, INRAE, UR EABX, INRAE, EPOC, SMGBL
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, 21/02/2026)
FURG, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EABX, INRAE
Highway runoff and wastewater effluents as drivers of platinum dynamics in an urban river: Insights from a comprehensive monitoring study
The contribution of a single rain event to daily and annual platinum (Pt) transport in an urban river (Jalle River, South-West of France), assessed from high resolution and annual monitoring, is discussed in terms of dissolved (Pt-d) and particulate (Pt-p) partitioning, sources and fluxes. In normal discharge conditions, the Jalle River Pt-d and Pt-p concentrations are respectively 1.90 +/- 1.62 ng L-1 and 19.8 +/- 6.9 mu g kg(-1) and Pt is mostly transported in the dissolved form (similar to 96 %, 110 +/- 123 mgPt(d) d(-1)), due to low sediment yield and urban discharges from a wastewater treatment plant (WWTP). The Pt-d flux in sewage (36-340 mgPt(d) d(-1)) was mainly attributed to excretions from patient undergoing chemotherapy with Pt-drugs (up to 480,000 mgPt(d) yr(-1) at the watershed scale). After a 2-months dry period, an intense rainstorm discharged >= 112 mg of Pt-p in 4 h from the urban highway, resulting in additional 295 mgPt(p) d(-1) exceptionally transported by the Jalle River. In contrast to normal conditions, during the rainstorm up to similar to 95 % of Pt was transported in particulate form during the first flush, and 80 % of the highway Pt-p flux during the first 40 min contributing to similar to one third of the annual Pt-p flux. Short, intense discharge events must be monitored at a high resolution to accurately estimate annual Pt fluxes in urban rivers.
(Applied Geochemistry. vol. 193, n° 0883-2927, 21/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, I2M-BX, UB, CNRS, INRAE
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, 21/02/2026)
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, UFC, 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
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, 21/02/2026)
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