Characterization of barchanoid dune systems on the Cap Ferret spit (Aquitaine)
The Cap Ferret spit (Atlantic coast, France) is defined by barchanoid dune systems formed by a large input of sand remobilized by aeolian dynamics. GPR investigations have revealed distinct internal architectures within the barchanoid dunes, mainly characterized by eastward-dipping reflectors and complex structures illustrating sand remobilization. These structures highlight a progressive evolution in dune morphology, from west to east, i) low topographic and interconnected dunes without specific morphology (proto-barchans), ii) interconnected dunes with crescent-shaped morphology (barchanoid ridge) and iii) isolated dunes with a well-defined crescent-shaped morphology (isolated barchans). This study investigates these distinct stages of development, linking internal stratigraphy and geomorphological evolution, and provides insights on the dynamics of coastal barchanoid dune formation and migration.
(. vol. 84, pp. 1-4, 11/07/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
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, 11/07/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LERAR, COAST, IFREMER, IRSTEA, LERPAC, COAST, IFREMER
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, 11/07/2026)
FURG, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EABX, INRAE
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, 11/07/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
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
Long‐Term Tectono‐Stratigraphic Evolution of a Propagating Rift System, L’Aquila Intermontane Basin (Central Apennines)
AbstractUnderstanding the long‐term tectono‐stratigraphic evolution of active extensional faulting is crucial for unraveling the mode through which continental rifting propagates in space and time. The Pliocene‐Quaternary L’Aquila Intermontane Basin (AIB) in central Apennines offers a natural laboratory for studying a propagating continental rift. Seismicity is related to NW‐SE‐striking normal faults that have been accommodating crustal stretching since the Late Pliocene. Through a multidisciplinary approach integrating field, mineralogical, geochemical (C‐O stable and clumped isotopes) and geochronological (40Ar/39Ar, U‐Th) analyses, this study focuses on the structural connection between the Mount Pettino Fault (MPF) and the Paganica Fault, two active, left‐stepped basin boundary faults of the AIB. A two‐stage tectono‐stratigraphic evolution is proposed during transition from localized to delocalized deformation and fault linkage. Stage‐1 (pre‐Middle Pleistocene) corresponds to nucleation and growth of the MPF, characterized by a ∼5 m thick exhumed fault core, consisting of an isotopically closed cataclasite (T (∆47) ∼33–50°C). Stage‐2 corresponds to the development of a distributed zone of NW‐SE and E‐W extensional faulting in the overlay zone with the Paganica Fault, which is interpreted as a transfer zone linking the basin boundary faults, with maximum long‐term slip rates comparable to those of the connected faults. Structurally controlled circulation of meteoric fluids promoted carbonate veining and travertine formation (T (∆47) ∼8°C). U‐Th carbonate dating of Stage‐2 mineralizations constrains the tectonic activity in the transfer zone at least at ∼182–331 ka. Implications on the tectono‐stratigraphic evolution and on the seismotectonic scenario of the AIB are discussed, providing geodynamic inference at regional scale.
(Tectonics. vol. 43, n° 0278-7407, 23/12/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Field investigation of spatio-temporal change of sediment grain size and beach slope on wave-dominated sandy beaches
Beach slope is a critical parameter which is usually assumed constant in time and to depend on a single time-invariant median grain size. In the present work, we conducted a three-year intensive in situ biyearly monitoring of the 3D distribution (surface and depth across a 50-cm profile) of sediment grain size and beach topography at five sandy beaches in France. These five beaches are representative of the diversity of the metropolitan France beaches in terms of wave climate, tide range, and anthropogenic pressure. Results show that, generally, average sediment grain size and beach slope are finer and more gently sloping at the end of the winter and at the end of the summer, respectively. Results also show a large spatial and temporal variability of both sediment grain size (horizontally and vertically) and of the sandy beach morphology. Sediment grain size shows a consistent vertical gradient, with finer sand closer to the surface. The spatial and temporal patterns of beach slope and beach sediment variability are found to be linked with beach state (dissipative, intermediate, reflective) and anthropogenic pressure at the engineered beaches. Our results also suggest that tide range and modal wave conditions must be considered to improve empirical models linking beach slope and sediment grain size.
(Journal of Coastal Research. vol. 113, n° 0749-0208, pp. 432-437, 20/12/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SHOM
Field Investigation of Spatio-Temporal Change of Sediment Grain Size and Beach Slope on Wave-Dominated Sandy Beaches
Beach slope is a critical parameter which is usually assumed constant in time and to depend on a single time-invariant median grain size. In the present work, we conducted a three-year intensive in situ bi-yearly monitoring of the 3D distribution (surface and depth across a 50-cm profile) of sediment grain size and beach topography at five sandy beaches in France. These five beaches are representative of the diversity of the metropolitan France beaches in terms of wave climate, tide range, and anthropogenic pressure. Results show that, generally, average sediment grain size and beach slope are finer and more gently sloping at the end of the winter and at the end of the summer, respectively. Results also show a large spatial and temporal variability of both sediment grain size (horizontally and vertically) and of the sandy beach morphology. Sediment grain size shows a consistent vertical gradient, with finer sand closer to the surface. The spatial and temporal patterns of beach slope and beach sediment variability are found to be linked with beach state (dissipative, intermediate, reflective) and anthropogenic pressure at the engineered beaches. Our results also suggest that tide range and modal wave conditions must be considered to improve empirical models linking beach slope and sediment grain size.
(Journal of Coastal Research. vol. 113, n° 0749-0208, 20/12/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Dynamique de la composition de la matière organique particulaire à l’interface continent-océan
La matière organique particulaire (MOP) joue un rôle clef dans le fonctionnement des écosystèmes constituant le continuum aquatique continent-océan. La MOP peut être composée de plusieurs sources produites in situ (phytoplancton, microphytobenthos, macroalgues) ou importées depuis les écosystèmes adjacents (MOP terrestre, MOP anthropique, phytoplancton fluvial, estuarien ou marin). Le long du continuum fluvio-estuarien, les proportions de chaque source dans la composition de la MOP varient au cours des saisons et entre les écosystèmes, fortement influencées par des processus environnementaux (ex. production primaire, sédimentation / remise en suspension, reminéralisation). L’objectif de cette thèse est d’améliorer (1) la caractérisation des signatures isotopiques et élémentaires des sources de MOP, (2) la quantification de la composition de la MOP provenant des fleuves et étant transformée dans les systèmes estuariens, (3) la description de la variabilité spatio-temporelle de la MOP et (4) la compréhension des forçages environnementaux à cette variabilité. Pour ce faire, la composition de la MOP a été estimée à l’aide de modèles de mélanges sur vingt-quatre systèmes fluvio-estuariens tempérés en utilisant les rapports isotopiques et élémentaires du carbone et de l’azote (δ13C, δ15N et C/N), ainsi que de l’hydrogène comme travail méthodologique prospectif (δ2Hn). La variabilité spatio-temporelle de chacune des sources de la MOP a ensuite été liée à des paramètres environnementaux à l’aide de statistiques multivariées pour en déterminer les forçages. Enfin, une comparaison des systèmes au regard de la dynamique de la composition de la MOP a été proposée. Quatre types ont été identifiés parmi les vingt-trois fleuves étudiés : (1) les fleuves à la MOP dominée par du matériel terrestre labile sur le cycle annuel, (2) les fleuves dont la MOP est composée de matériel terrestre labile et de phytoplancton, avec une saisonnalité marquée due à des efflorescences saisonnières ou bien (3) sans saisonnalité marquée, et enfin (4) les fleuves à la MOP composée de MOP terrestre labile, réfractaire et de phytoplancton, en lien avec des conditions saisonnières contrastées. Les cinq estuaires étudiés présentent des dynamiques de compositions de MOP contrastées. Dans l’Elorn et la Leyre la MOP fluviale est remplacée aux faibles salinités par du phytoplancton produit dans l’estuaire toute l’année. L’Aulne fonctionne de manière similaire mais transporte plus en aval la MOP fluviale dans des conditions hivernales. L’estuaire de la Loire présente une MOP composée uniquement de MOP autotrophe, vivante au printemps ou dégradée en hiver. Enfin, l’estuaire de la Gironde présente une MOP dominée par du matériel terrestre réfractaire sur tout le cycle annuel. Le long du continuum fluvio-estuarien, la MOP fluviale présente une composition et une dynamique spatio-temporelle contrastée. Cette MOP apportée par les fleuves voit sa composition ensuite transformée le long de l’estuaire sous une forme réfractaire par dégradation et/ou est additionnée de MOP vivante autotrophe produite in situ.
(17/12/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS