Application of a data-model assimilation method to a 3D surf zone sandbar physical experiment
Video imagery recently arose as a low-cost alternative to direct measurement to estimate wave characteristics and then tackle the lack of actual updated bathymetries hydro-morphodynamic coupled numerical models typically face. Nonlinearities that are ubiquitous over complex three-dimensional surfzone sandbars are a key problem for observation relevance, and feed an increasing need of local wave information. Therefore, a close interaction between video imagery and modeling is highly required through observation assimilation. In this paper, we explore two bathymetry inversion methods related to an original experiment on nature-like beaches. Wave celerity was first video-estimated and depth inversion was performed to quantify the underlying bathymetry. While existing methods were previously tested over rather alongshore-uniform barred beaches, here we show that the efficiency of such method strongly decreases with increasing beach alongshore non-uniformity. A data-model assimilation, based on a Kalman filter, was further developed and applied to our experimental study using bathymetric data that derived from wave celerity estimates. Analytically set Gaussian-type covariance matrices were inverted to provide local correction. The method shows promising skills to correct bathymetry with the single source of bathymetric video proxy and now required further in-depth improvement.
(Journal of Coastal Research. vol. SI 64, n° 0749-0208, pp. 976-980, 28/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGI, UJF, Grenoble INP, CNRS
The ECORS-Truc Vert'08 nearshore field experiment: presentation of a three-dimensional morphologic system in a macro-tidal environment during consecutive extreme storm conditions
A large multi-institutional nearshore field experiment was conducted at Truc Vert, on the Atlantic coast of France in early 2008. Truc Vert'08 was designed to measure beach change on a long, sandy stretch of coast without engineering works with emphasis on large winter waves (offshore significant wave height up to 8 m), a threedimensional morphology, and macro-tidal conditions. Nearshore wave transformation, circulation and bathymetric changes involve coupled processes at many spatial and temporal scales thus implying the need to improve our knowledge for the full spectrum of scales to achieve a comprehensive view of the natural system. This experiment is unique when compared with existing experiments because of the simultaneous investigation of processes at different scales, both spatially (from ripples to sand banks) and temporally (from single swash events to several spring-neap tidal cycles, including a major storm event). The purpose of this paper is to provide background information on the experiment by providing detailed presentation of the instrument layout and snapshots of preliminary results.
(Ocean Dynamics. vol. 61, n° 1616-7341, pp. 2073-2098, 28/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LASAGEC, UPPA, LEGI, UJF, Grenoble INP, CNRS, IMAU, LSEET, INSU - CNRS, UTLN, CNRS, SHOM, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, IMAGES, UPVD, BRGM
HFNI Valvometry : a tool based on recording bivalve ethology to monitor environmental health in coastal seawaters
(28/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMBA, UBS, UBO EPE, CNRS
The 7–13 March 2006 major Saharan outbreak: Multiproxy characterization of mineral dust deposited on the West African margin
Mineral dust deposits were collected at Mbour, Senegal, throughout the spring of 2006 and especially during the well‐documented March 7–13 large Saharan dust outbreak. During this 7‐day period, significant changes in mass flux, grain‐size, clay mineralogy and Sr and Nd isotopic compositions were recorded, indicating distinct provenances for the dust transported and deposited during and outside the event. All these terrigenous proxies, as well as freshwater diatom taxa, also showed significant temporal variations during the outbreak, implying contributions from at least two different provenance regions. Tri‐dimensional back‐trajectories and satellite imaging enabled us to link those distinct signatures to regions increasingly to the southeast within a large area covering Mauritania, Mali and southern Algeria, identified by the Total Ozone Mapping Spectrometer (TOMS) as the main source of the prominent winter/spring plume over the tropical Atlantic. The multiproxy characterization of the March 7–13 dust fall therefore enables us to typify the terrigenous signature of two different regions supplying dust off West Africa, and provide valuable clues for the interpretation of Northeastern Tropical Atlantic Ocean dust sedimentary records in terms of changes in provenance regions and transport systems. Additionally, because dust deposition data are scarce, flux and grain size data obtained in this study, among other parameters such as clay assemblages, provide important constraints for atmospheric transport models and dust deposition budget estimates in this area.
(Journal of Geophysical Research: Atmospheres. vol. 116, n° 2169-897X, pp. D18210, 28/10/2026)
LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], CNRS, MPIC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, NIOZ, LOA, INSU - CNRS, CNRS, LISA (UMR_7583), INSU - CNRS, UPD7, UPEC UP12, CNRS, IMAGO
In situ giant clam growth rate behavior in relation to temperature : a one-year coupled study of high-frequency noninvasive valvometry and sclerochronology
The life history of 15 giant clams, Hippopus hippopus, was studied in situ in the southern lagoon of New Caledonia; growth rate and animal behavior were studied both by sclerochronology and high-frequency noninvasive (HFNI) valvometry. Electrodes glued on each valve of each specimen recorded the shell-gaping behavior at 0.6-Hz frequency. A nonparametric regression model was used to model clam behavior. The daily increment thickness in the inner layer of five representative clams was measured. H. hippopus has its valves open during the day and partly closed during the night all year round, and shell growth is continuous. The cumulative growth using both techniques was similar, as was the mean daily thickness increment. The occurrence of one increment per day in H. hippopus shell was measured by valvometry. The five sclerochronological profiles were highly similar. Shell growth was significantly correlated to rising sea surface temperature (SST), up to 27 degrees C. At the solar maximum, gaping behavior and increment thickness became erratic. SST- and solar irradiance-related stress could be related to physiological oxidative stress triggered by zooxanthellae symbionts. In the present context of globally increasing SST, our data indicate that the giant clams H. hippopus could live beyond their thermal comfort limits in summer in New Caledonia.
(Limnology and Oceanography. vol. 56, n° 0024-3590, pp. 1940-1951, 28/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, LMBA, UBS, UBO EPE, CNRS
Presence of Palaemon macrodactylus in a Europe estuary: evidence for a successful invasion of the Gironde (SW France)
Palaemon macrodactylus, an exotic shrimp native to the northwest Pacific Ocean, has been recorded in many estuaries along the Atlantic coast of Europe since the late 1990’s. In this study, a regular monthly survey, held since 1992 of the middle section of the Gironde estuary, revealed this species’ rapid and full colonization of the system since its appearance in samples during summer 1998. In the Gironde, the population of P. macrodactylus is self-sustaining and the species is now established there. Our study highlights two important elements that might explain its successful colonization: its ability to quickly invade a niche under-exploited by the similar native species and its greater reproductive output. The species’spatio-temporal distribution in relation to environmental variables was studied and compared with that of the native species P. longirostris. The exotic species was shown to mainly inhabit the polyhaline and mesohaline section of the estuary, which are sections generally under-exploited by females of the native species. Furthermore, fecundity analysis and larval abundance survey results revealed a higher potential fecundity and a greater proportion of larvae and juvenile stages for P. macrodactylus in the natural environment.
(Aquatic Invasions. vol. 6, n° 1798-6540, pp. p. 301 - p. 318, 28/10/2026)
UR EPBX, CEMAGREF, UR MALY, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Mesurer les micropolluants dans les eaux usées brutes et traitées. Protocoles et résultats pour l'analyse des concentrations et des flux
Le projet AMPERES a permis une évaluation des concentrations et des flux de 127 substances prioritaires et émergentes dans les eaux usées brutes, les eaux traitées et les boues pour différentes filières d'épuration représentatives du parc français par une démarche de prélèvement et d'analyse rigoureuse et validée. Au total, 21 stations d'épuration (STEP) ont été sélectionnées pour étudier les traitements biologiques secondaires, plusieurs procédés tertiaires et les filières de traitement des boues. Des prélèvements moyen-24h des eaux résiduaires ont été réalisés par temps sec au cours de 2 à 3 jours consécutifs en entrée et en sortie de STEP. Nous avons développé et appliqué des protocoles analytiques spécifiques pour la mesure des substances en phase dissoute et particulaire, sensibles et adaptés aux matrices des STEP qui présentent une forte complexité. Les substances présentes aux plus fortes concentrations (>1 µg/L) dans les eaux usées brutes sont le DEHP, certains composés organiques volatiles (COV), des retardateurs de flammes (diphényléthersbromés ou PBDE), les alkylphénols (4-NP et 4-t-OP et leurs produits de dégradation, et presque tous les métaux. Les niveaux de concentration dans les eaux usées brutes et les flux spécifiques montrent une spécificité des rejets des STEP de zone urbaine par rapport aux STEP de zone rurale pour certaines substances d'origine industrielle (alkylphénols, COV, chloroalcanes, dichlorophénol, bisphénol A et quelques métaux). Dans les eaux traitées par traitement biologique, même si une réduction significative des concentrations par rapport à l'eau usée brute est généralement observée, 12 substances prioritaires, 10 autres substances organiques et la plupart des métaux ont encore été retrouvées à des concentrations moyennes supérieures à 0,1 µg/L. Des concentrations supérieures à 1 µg/L ont été fréquemment mesurées pour plusieurs métaux, le DEHP et certains produits de dégradation (4-NP1EC et AMPA). Pratiquement toutes les substances qui ont été quantifiées dans les eaux usées brutes, l'ont aussi été dans les boues, même si elles sont parfois mesurées à de très faibles concentrations, en particulier pour les substances les plus hydrophiles (pesticides). Cet article présente également les données exploitées sous la forme de flux spécifiques (µg/j/hab) émis vers les milieux récepteurs.
(TSM. Techniques Sciences Méthodes. vol. 1-2, n° 0299-7258, pp. 25-43, 28/10/2026)
RiverLy, INRAE, UR MALY, CEMAGREF, UR REVERSAAL, INRAE, CNRS, LPTC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CIRSEE
Acoustic turbulence measurements of near-bed suspended sediment dynamics in highly turbid waters of a macrotidal estuary
Sediment-turbulence interactions near the bed are still poorly understood in highly turbid estuaries, especially in the presence of fluid mud layers. This results primarily from the difficulty in measuring colocated velocity and suspended sediment concentration (SSC) at sufficiently high rate to resolve small turbulent flow scales. In this paper, we show how a set of commercial acoustic and optical backscattering systems known as ADCPs, ADVs and OBSs, can be deployed and used in a complementary way to perform large-scale profilings of tidal current and SSC combined with high-resolution velocity and SSC measurements in the highly turbid near-bed zone. The experiment was done in the Gironde estuary (France) which is well known for its turbidity maximum zone characterized by high SSC values, above 1 g/l near the surface. A first simple inversion method is proposed to convert the backscattered acoustic intensity measured with ADV into SSC data in the highly turbid near-bed zone. Near-bed SSC data from the OBS are used to compensate for the important acoustic sediment attenuation effect at an acoustic frequency of 6 MHz. No a priori knowledge of acoustic backscattering properties of mud suspensions is required with this calibration procedure. We obtain an attenuation coefficient for mud suspensions of 0.28m2/kg at 6 MHz leading to a good agreement between the SSC timeseries from the three ADV receivers and the OBS over the entire tidal cycle. The obtained SSC data are then analyzed with respect to the near-bed velocity, Reynolds shear stress and turbulent kinetic energy (TKE) timeseries in order to identify the relevant sediment transport processes during the tidal cycle. Significant differences in bed shear stress and TKE levels are found between ebb and flood stages with effects on near-bed sediment dynamics. During the ebb, maximum levels of tidal current, bed shear stress and TKE are associated with a reduction of near-bed sediment concentration (from 400 g/l down to 100 g/l). Bed liquefaction process is assumed to occur at this moment with the presence of highly concentrated mud layer and a possible lutocline at a distance of less than 20 cm above the bed. During the first 1.5 h of flood, turbulent activity remains moderate. The near-bed flood current is then inhibited very abruptly while a sudden increase in SSC occurred above the bed. Assuming that the ADV is able to estimate relevant turbulent erosion fluxes, the co-located velocity and SSC are multiplied and compared with settling flux measurements made onboard under quiescent water conditions. The mean sediment settling fluxes (averaged over 3min) increase with SSC and are in relative good coherence with fluxes in quiescent water below the hindered regime, for SSC below 15 g/l. Reducing averaging time from 3 min to 30 s allows to increase the range of turbulent fluxes and SSC values, up to 99 g/l. At this scale, fluxes keep increasing quasi-linearly at higher SSC, suggesting the inhibition (delay or reduction) of the hindered settling regime as previously shown by Gratiot et al. (2005) from laboratory experiments. However, the 3-min averaged concentration field remained too low to conclude definitively on the effectiveness of such a process. Further analysis conducted at higher SSC regimes and under fully verified equilibrium are necessary.
(Continental Shelf Research. vol. 31, n° 0278-4343, pp. S36-S49, 28/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGI, UJF, Grenoble INP, CNRS, LTHE, OSUG, UJF, Grenoble INP, INSU - CNRS, IRSTEA, USMB [Université de Savoie] [Université de Chambéry], CNRS, IRD, INSU - CNRS, INPG, CNRS, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS
Distribution of parasites in their second intermediate host, the cockle Cerastoderma edule: community heterogeneity and spatial scale
We studied the spatial heterogeneity of infection of the marine bivalve Cerastoderma edule (cockle) by trematode parasites at 5 different scales in Banc d’Arguin, France. At the km-scale, the communities of trematodes differed among stations in terms of species composition and specific abundance. Infection heterogeneity was likely due to the occurrence of the definitive host and the conditions of transmission (water parameters). At the 100 m scale, trematode species richness was similar among stations, but specific trematode abundances differed. The most significant variable in terms of explaining trematode infection heterogeneity was the presence of the first intermediate host. At the 10 m scale, the distance at which parasite abundance diminished varied according to trematode species. When an intense source of trematode larvae (cercariae) emission was suspected, this abundance was maintained within ca. 20 m. Outside this area, parasite abundance progressively dropped. We found a higher aggregation in parasite distribution at the 100 m scale than at the 10 m scale using a community aggregation measure. At the cm-scale, the parasite species richness was similar in all cockles but parasite abundance differed in relation to distance when the parasites were shed by a sedentary host compared to a motile host. Observed differences of infection could also be due to intrinsic factors (life history, immune system) as suggested by an experimental infestation where cockles challenged in similar conditions displayed different parasite loads. We demonstrated that high heterogeneity of parasite infection in cockles should be taken into account in studies concerning the role of parasites in ecosystems.
(Marine Ecology Progress Series. vol. 428, n° 0171-8630, pp. 187-199, 28/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Capacités de décontamination métallique et évolution des formes tératogènes de Planothidium lanceolatum après une contamination expérimentale au cadmium
Cette étude vise à évaluer la viabilité des formes tératogènes et leurs capacités de reproduction après une contamination métallique afin de prédire un éventuel retour vers une population diatomique de forme normale. Nous avons travaillé sur une espèce fréquemment rencontrée dans les hydrosystèmes français : Planothidium lanceolatum. Une première phase expérimentale a consisté à contaminer des monocultures en Cd à 20 ou 100 ag/L pendant 21 jours. Cela a permis de mettre en évidence l'induction de formes tératogènes en réponse à la contamination en Cd. L'identification des tératologies indique que le Cd affecterait en premier lieu le raphé, les stries puis les valves. Les déformations de l'aire centrale et les tératologies multiples semblent se produire en second lieu. A la suite de la contamination, une seconde phase expérimentale s'est déroulée durant 28 jours en condition de décontamination. Elle a permis de démontrer les capacités de dépuration en Cd de Planothidium lanceolatum. Les demies-vies du Cd calculées sont apparues relativement courtes : environ 6 jours pour la condition initialement contaminée à 100 ag/L. Par ailleurs, la décontamination des monocultures a permis de mettre en évidence une disparition progressive des formes tératogènes, néanmoins restée incomplète en fin d'expérience. Ainsi, après 28 jours de décontamination, les déformations des stries et du raphé restaient encore statistiquement supérieures aux conditions témoins dans les deux conditions initialement contaminées à 20 et 100 ag/L. Des études complémentaires intégrant d'autres espèces de diatomées seraient donc nécessaires pour comparer les différentes capacités de dépuration métallique et de retour vers des formes normales. Enfin, une phase de décontamination plus longue et progressive permettrait d'estimer le temps nécessaire pour un rétablissement complet de la population et imiterait de façon plus représentative une éventuelle amélioration chimique du milieu comme observé in situ.
(pp. 1, 28/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR REBX, CEMAGREF