Influence de la morphologie dunaire sur les flux éoliens et le transport sédimentaire : Exemple sur la côte Aquitaine
L'évolution des dunes côtières est d'une importance stratégique vis-à-vis du risque de submersion dans un contexte d'érosion de nombreux littoraux sableux. Leur dynamique est contrôlée par les interactions complexes entre les facteurs biotiques et abiotiques, notamment le vent incident, la morphologie de la dune et la densité de végétation. La littérature décrit les caractéristiques du vent lors du franchissement d'un système plagedune ainsi que du transport sédimentaire associé pour de nombreux environnements. Toutefois, il n'est pas documenté à ce jour, comment deux systèmes à la morphologie contrastée répondent à une même tempête. Dans ce cadre, une campagne de terrain de 3 jours a été réalisée sur deux sites voisins de la côte Aquitaine (La Teste-de-Buch (S1) et Biscarrosse (S2)) en simultanée. Ils présentent des morphologies contrastées avec une dune fixée par la végétation au front dunaire abrupte (36°) en S1 et une dune libre, au profil doux (11°) en S2. L'étude repose sur l'acquisition de données de vent à l'aide de 21 anémomètres répartis sur les deux sites d'étude, complétée en plusieurs endroits par l'analyse qualitative de panaches de fumigènes capturés par vidéo. Enfin, des mesures de transport sédimentaire ont également été réalisées en différentes positions sur le long des profils. Les résultats mettent en évidence le rôle de la morphologie sur le comportement du vent lors du franchissement de la dune favorisant en S2 un transport sédimentaire pouvant atteindre 200 kg/m²/h au niveau de la crête. Les sédiments transportés proviennent de la plage et de l'érosion de la face marine de la dune. A contrario, l'impact de la face très abrupte de la dune de S1 sur le vent limite très fortement le transport sédimentaire de la plage vers le haut de la dune. Ainsi, la morphologie de S2 favorise le transfert sédimentaire de la plage vers les terres permettant sur des secteurs en érosion le maintien d'un milieu dunaire dans le temps.
(23/02/2026)
UPVD, CEFREM, UPVD, INSU - CNRS, CNRS, ISMO, CNRS, BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ONF
Incisocalliope aestuarius (Crustacea: Amphipoda: Pleustidae), an old introduced species in the Gironde Estuary (SW France)
The amphipod Incisocalliope aestuarius was recently collected since 2015 in the mesohaline part of the Gironde Estuary (SW France) with a van Veen grab and in the lower intertidal part in oyster bed by hand-picking. A look back at past studies showed that this species was present in this estuary since 1976, whereas the original description of this amphipod comes from Watling and Maurer in 1973, from the East coast of America. The validity of the Incisocalliope genus is herein questioned, and it is proposed to transfer species of the genus Inciscalliope to Parapleustes genus.
(Journal of the Marine Biological Association of the United Kingdom. vol. 104, n° 0025-3154, pp. e116, 23/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ISYEB, MNHN, EPHE, PSL, SU, CNRS, UA, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE
Sedimentology of Modern Bahamian Carbonate Slopes: Summary and Update
Slopes adjacent to the Bahamian carbonate platform revealed a large variety of depositional processes. In this study, we present a synthesis summarizing 109,000 km2 of bathymetric and reflectivity data with ∼7,900 km of seismic lines and 311 m of sediment cores that were obtained over the last 50 years. These data are used to develop a conceptual model of sedimentation patterns on Quaternary carbonate slope systems and their interaction with the adjacent shallow-water carbonate platforms. Our data highlight that during the Quaternary, factors controlling large-scale sedimentation on Bahamian slopes have numerous similarities as they have higher sedimentation rates during interglacials. At a small scale, every slope has its own characteristics that are contemporary controlled by two main characteristics: (a) facies on the adjacent shallow-water platform, and (b) the impact of shallow- and deep-water currents. Large-scale tectonics influence sediment deposition as it determines the position of the islands and impacts platform facies distribution.
(Geochemistry, Geophysics, Geosystems. vol. 25, pp. 6, pp. 265-290, 23/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, OSU PYTHEAS, IRD, AMU, INSU - CNRS, CNRS, INRAE, [Total Energies. Anciennement : Total, TotalFina, TotalFinaElf], CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE
Transport of microplastic debris in estuaries
This Chapter provides insight into the physical, hydrodynamic and biochemical processes governing the transport of microplastics in estuarine environments. The focus is mainly on the physical and hydrodynamical processes that control microplastic transport, although the role of biochemical processes on their dynamical behaviour is discussed. The chapter begins by describing the microplastic physical properties and their variability with the time spent in the environment due to weathering, biofouling, and flocculation. This variability makes them different from other suspended particulate matter and critically affects their buoyancy, deposition and erosion rates. The more prominent hydrodynamic processes driving the transport of microplastics are then discussed. Next, four case studies are presented to illustrate microplastic dynamics in different types of estuaries, from well-mixed to strongly stratified. Finally, sampling and numerical approaches for analysing the dispersion of microplastics in estuaries are reviewed.
(. vol. 2, 23/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UGR
Comparing the evolution of debris-free and debris-covered glaciers during the end of the Lateglacial and the Holocene in Dudh Koshi basin, Everest region, Nepal
Debris-covered glaciers are very frequent geomorphological features in Khumbu Himal (Nepal). Rock debris on the glacier surface play a significant role in glacier-climate relationships and glacier dynamics. These effects may cause an asynchronous evolution of debris-covered glaciers compared to debris-free glaciers at a multicentennial to millennial scale. Here, we explore this hypothesis by documenting and comparing the multi-millennial Holocene evolution of a debris-free glacier, Sabai glacier, and two debris-covered glaciers, Dig and Huuku glaciers, from adjacent catchments in Dudh Koshi basin (Everest region, Nepal). To do so, we dated rock samples collected from moraine boulders on both debris-covered and debris-free glaciers using the 10Be cosmic ray exposure (CRE) dating method. 10Be CRE ages obtained from 41 moraine boulder samples provide time constraints from ∼13.5 ka to 0.1 ka. While at Dig (debris-covered) and Sabai (debris-free) glaciers, no moraines from the Lateglacial and the Early Holocene are preserved, debris-covered Huuku glacier evidenced a large glacier extent during the Bølling-Allerød and Early Holocene with two moraines dated respectively to ∼13.5 ka and 11 ka, synchronously with most debris-free and debris-covered glaciers in this region. These two glacier advances are concomitant with enhanced monsoon precipitation supporting a qualitative relationship. The absence of debris landforms in the main valley question the nature of Huuku glacier during the Bølling-Allerød and Early Holocene, which could have been either debris-free or covered by a thin debris layer only. During the Mid Holocene, significant differences are observed in the evolution of the two glacier types. The two debris-covered glaciers recorded a significant advance at ∼4.8 ka, synchronous with that observed on other debris-covered glaciers in Khumbu valley. However, such glacier advance during the Mid Holocene was not evidenced on debris-free glaciers in the Dudh Koshi valley. Such a Mid Holocene glacier advance may have a spatial signature with frequent cases reported from both types of glaciers in the western part of High Mountain Asia, which are however infrequent in the arid and semi-arid southern and north-eastern Tibet. During the Late Holocene, both types of glaciers evolved similarly again, with moraines spanning the last two millennia, including the Little Ice Age, concomitant with enhanced monsoon precipitation.
(Quaternary Science Reviews. vol. 344, n° 0277-3791, pp. 108994, 23/02/2026)
CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE, IGE, IRD, INSU - CNRS, CNRS, INRAE, Fédération OSUG, UGA, Grenoble INP, UGA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Potential impacts of cable bacteria activity on hard-shelled benthic foraminifera: implications for their interpretation as bioindicators or paleoproxies
Hard-shelled foraminifera are protists able to build a calcareous or agglutinated shell (called a “test”). Here we study the impact of sediment acidification on calcareous test preservation. For this study, sediment cores were sampled in the macrotidal Auray estuary located on the French Atlantic coast. Living and dead foraminifera were quantified until 5 cm depth and discriminated using the Cell-Tracker™ Green vital marker. The pH and oxygen profiles combined with quantitative polymerase chain reaction (qPCR) suggested that cable bacteria were most likely to cause the acidifying process. Cable bacteria (CB) are filamentous bacteria coupling sulfide oxidation to oxygen reduction over centimetre distances, generating a strong pH gradient within the first few centimetres of the sediment that could affect the microhabitats occupied by benthic foraminifera. On two different intertidal mudflats, volumetric filament densities have been estimated. They were comparable to those observed in the literature for coastal environments, with 7.4 ± 0.4 and 74.4 ± 5.0 m cm−3 per bulk sediment, respectively. Highly contrasting sediment acidification (from low to very intense) was described from 1.0 to 2.4 ΔpH. This seems to lead to various dissolution stages of the foraminiferal calcareous test from intact to fully dissolved tests revealing the organic lining. The dissolution scale is based on observations of living Ammonia spp. and Haynesina germanica specimens under a scanning electronic microscope. Furthermore, dead foraminiferal assemblages showed a strong calcareous test loss and an organic lining accumulation throughout depth under low pH, hampering the test preservation in deep sediment. These changes in both living and dead foraminiferal assemblages suggest that cable bacteria must be considered in ecological monitoring and historical studies using foraminifera as bioindicators and paleoenvironmental proxies.
(Biogeosciences. vol. 21, n° 1726-4170, pp. 911-928, 23/02/2026)
LPG-ANGERS, LPG, UM, UA, INSU - CNRS, CNRS, Nantes univ - UFR ST, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Investigating beachgoer’s perception of coastal bathing risks in southwest France
Sandy beaches offer numerous health and well-being benefits, but engaging in water-based recreational activities also exposes beachgoers to risks from natural hazards, such as rip currents and waves that break at the shoreline (shore break waves), which can result in fatal drownings and surf zone injuries. A contributing factor to these incidents is that individuals often misunderstand the risks they are exposed to. This study used a unique multidisciplinary database combining beachgoer surveys, marine and weather data and lifeguard hazards assessments to examine beachgoer’s risk perception at a beach located in southwest France. We identified a number of factors that can have potentially contradictory influences on beachgoers’ perceptions. Beachgoers’ perceived risk of rip current and shore break hazards increases with increasing wave height and increasing wave period. Tide level has a significant statistical influence on individuals’ perceived risk of the shore break wave hazard only. Beachgoers familiar with La Lette Blanche beach had higher rip current and shore break risk perceptions although regular recreational beach users (in general) tend to underestimate risks. Similarly, males and younger people express lower perceived risks compared to others. For a large number of environmental conditions, beachgoers perceive rip currents to be a greater risk than shore breaks wave risks although they tend to overestimate beach hazards compared to lifeguards. These results create new avenues for preventive communication, in particular by emphasizing the danger of shore breaks, and the specific nature of the risks on the beaches of south-west France. Some of these safety messages should communicated well before the beachgoers arrive at the beach.
(Natural Hazards. vol. 120, n° 0921-030X, pp. 13209–13230, 23/02/2026)
UR ETTIS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNSW
Observation et modélisation de la dynamique pluriannuelle des cordons dunaires en Gironde
Considérées comme des réservoirs de biodiversité, les dunes côtières représentent également des barrières naturelles contre la submersion marine et de larges sources de sable modérant l'érosion du trait de côte. Leur évolution dépend de nombreuses interactions complexes entre des processus marins, éoliens et biologiques. L'analyse de données d'observation collectées le long de cordons dunaires à une échelle pluriannuelle, et leur utilisation pour calibrer et valider des modèles numériques, permettent de mieux comprendre ces interactions. Cette étude a montré que le modèle AeoLiS était capable de reproduire, de manière satisfaisante, la migration pluriannuelle de deux cordons dunaires peu végétalisés sur de la côte girondine. En revanche, la végétation joue un rôle prépondérant dans l'évolution de cordons dunaires et sera intégrée dans le cadre du modèle lors de futurs travaux.
(23/02/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB, BRGM
Modélisation à complexité réduite de l’impact du phénomène de bypass sédimentaire sur la dynamique des plages de poche
Le phénomène de bypass sédimentaire peut considérablement influencer la dynamique des plages de poche à moyen et long terme. Cependant, il n’est encore que partiellement inclus dans les modèles d’évolution du trait de côte à complexité réduite. Ici, une paramétrisation du flux de sédiments qui contournent (« bypass ») un obstacle rocheux est implémentée dans le modèle LX-Shore. Les simulations effectuées sur le cas académique d’une plage initialement rectiligne bordée par deux épis rocheux montrent que le transport des sédiments autour de l’obstacle dans la colonne d’eau (ou « full bypassing », FB) impacte significativement la forme moyenne et la variabilité spatiale du trait de côte par rapport au bypass se produisant uniquement lorsque le trait de côte franchit la pointe de l’ouvrage (ou « shoreline bypassing », SB). L’angle de rotation de la plage est réduit d’environ 1/3, en particulier en cas de climat de vagues peu obliques et asymétriques. La courbure de la plage est également significativement réduite, surtout en cas de forçage très oblique et asymétrique. Enfin, le maximum d’érosion en amont de l’ouvrage est surestimé jusqu’à 30% en configuration SB par rapport à FB. Ces résultats soulignent l’importance de l’influence du bypass sédimentaire sur la dynamique des plages de poche et la nécessité d’intégrer des paramétrisations de ce phénomène dans les modèles à complexité réduite.
(pp. 303-310, 23/02/2026)
BW-CGC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BRGM
Resource partitioning of a Mexican clam in species-poor Baltic Sea sediments indicates the existence of a vacant trophic niche
Invasive species are often generalists that can take advantage of formerly unexploited resources. The existence of such vacant niches is more likely in species-poor systems like the Baltic Sea. The suspension feeding wedge clam, Rangia cuneata, native to estuarine environments in the Gulf of Mexico, was sighted for the first time in the southeastern Baltic in 2010 and a few years later in the northern Baltic along the Swedish coast. To explore possible competition for food resources between R. cuneata and the three native clams inhabiting Baltic shallow soft bottoms, stable isotope and fatty acid analyses were conducted. There was no overlap between R. cuneata and any of the native species in either stable isotope or fatty acid niches. This suggests efficient partitioning of resources; multivariate analyses indicate that separation was driven mainly by δ$^{13}$C and by fatty acids reflecting diatoms and cyanobacteria, respectively (e.g. 16:1ω7 and 18:3ω3). R. cuneata reflected seasonal variation in phytoplankton more than other clams reflecting higher trophic plasticity. In conclusion, the addition of R. cuneata to the Baltic shallow soft bottoms suggests the existence of a vacant trophic niche in these sediment habitats, however the long-term effects on other species and nutrient cycling requires further studies focusing on the population dynamics of R. cuneata and its impact on the Baltic Sea ecosystem
(Scientific Reports. vol. 14, n° 2045-2322, pp. 12527, 23/02/2026)
FTMC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS