A Bayesian approach to estimate biodynamic model parameters: bioaccumulation of PCB 153 by the freshwater crustacean Gammarus fossarum
The first step to evaluate the effects of contamination on organisms is to study toxicokinetics. The bioaccumulation of contaminants by aquatic species is a variable phenomenon, since it depends on the characteristics of the environment, the properties of the contaminants and the species. Different toxicokinetic models have been developed to describe the accumulation of contaminants in aquatic food webs. In these models, the organism is often considered as a single compartment: the bioaccumulation is then described as the balance between uptake and elimination processes. The absorption process can involve both dissolved or trophic route. The diet of aquatic organisms is known to be an important route of bioaccumulation of contaminants. The elimination process includes excretion, metabolism and dilution by growth. To date, there are few models focusing on persistent organic contaminants. Furthermore, estimating models' parameters is generally done through a frequentist approach in two steps: first by estimating parameter(s) related to depuration and then estimating parameter(s) related to accucumulation. The problem by doing this is that depuration during the accumulation phase is neglected, while this process occurs in the two phases. The aim of our study is to propose a Bayesian framework to estimate the parameters of a biodynamic model together by considering simultaneously accumulation and depuration data. The posterior distribution obtained for all parameter will enable a more accurate assessment of bioaccumulation uncertainty. We illustrate our approach with the freshwater benthic invertebrate Gammarus fossarum exposed for 7 days to a sediment spiked with PCB153 and transferred to a clean media for 7 more days. The PCB153 concentrations in Gammarus fossarum increased from an initial concentration of 0.32 to 12.36 ng.g-1 ww (wet weight) at the end of accumulation step. When gammarids were transferred into a clean media, the PCB153 concentration in organisms decreased to 6.41 ng.g-1 ww at day 14. The bioaccumulation model assuming first-order kinetics was fitted to the data using Bayesian inference. The inference process quickly converged and thin posterior distributions were obtained for each parameter, meaning that data brough enough information to estimate preciselly each parameter. The median model predictions and their 95% credibility intervals showed a good fit of the model to the data.
(pp. 1, 28/04/2026)
IRSTEA, LBBE, UCBL, VAS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
FAME (v1.0): a simple module to simulate the effect of planktonic foraminifer species-specific habitat on their oxygen isotopic content
The oxygen-18 to oxygen-16 ratio recorded in fossil planktonic foraminifer shells has been used for over 50 years in many geoscience applications. However, different planktonic foraminifer species generally yield distinct signals, as a consequence of their specific living habitats in the water column and along the year. This complexity is usually not taken into account in model-data integration studies. To overcome this shortcoming, we developed the Foraminifers As Modeled Entities (FAME) module. The module predicts the presence or absence of commonly used planktonic foraminifers and their oxygen-18 values. It is only forced by hydrographic data and uses a very limited number of parameters, almost all derived from culture experiments. FAME performance is evaluated using the Multiproxy Approach for the Reconstruction of the Glacial Ocean surface (MARGO) Late Holocene planktonic foraminifer cal-cite oxygen-18 and abundance datasets. The application of FAME to a simple cooling scenario demonstrates its utility to predict changes in planktonic foraminifer oxygen-18 to oxygen-16 ratio in response to changing climatic conditions.
(Geoscientific Model Development. vol. 11, n° 1991-9603, pp. 3587-3603, 28/04/2026)
LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Wilkes Land Late Pleistocene diatom age model: From bio-events to quantitative biostratigraphy
A new method merges conventional and quantitative biostratigraphic approaches, supported by magnetic polarity data, to develop a chronological framework for sediment core MD03-2595 retrieved on the continental rise off Wilkes Land, East Antarctica before proceeding to paleoceanographic and paleoclimatic analysis. This combined method helped to identify climatic cycles, highlight stratigraphic discontinuities and reworking, and assess regional sedimentological and diatom biostratigraphic evolution. Core MD03-2595 spans the last 0.8 Ma, from the Mid Pleistocene Transition (MPT) to the Early Holocene. A hiatus including Marine Isotope Stages (MIS) 19, 18 and 17 was identified, and a decreasing trend in sediment accumulation rates from MIS 16 to the Holocene was observed. This quantitative diatom biostratigraphic dataset, placed in its own sedimentological and paleomagnetic context, provides new information regarding the paleobiogeographic distribution and ecological responses of biostratigraphically significant diatom species, such as Thalassiosira elliptipora and T. fasciculata, for the Matuyama-Brunhes (M-B) transition, and Actinocyclus ingens, Hemidiscus karstenii and Rouxia spp. for the middle and late Pleistocene diatom biozonation.
(Revue de Micropaléontologie. vol. 61, n° 0035-1598, pp. 81-96, 28/04/2026)
UniGe, INGV, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Bref panorama scientifique de l'estuaire de la Gironde 2018
L'intérêt pour cette synthèse s'est développé en réponse au constat partagé avec les acteurs de la société d'un besoin de bilan des connaissances. Ce document est le fruit d'une démarche pluridisciplinaire des « Sciences du milieu» et des « Sciences humaines et sociales». Cet ouvrage de synthèse des connaissances s'inscrivant dans une démarche globale de partage des connaissances (et des interrogations), nous espérons qu'il permettra d'identifier de nouvelles réponses, mais aussi des lacunes, qui conduiront à des développements ultérieurs tant du point de vue de la recherche que de la gestion.
(pp. 55, 28/04/2026)
UB, IRSTEA, UR ETBX, IRSTEA, UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Refining uptake and depuration constants for fluoroalkyl chemicals in Chironomus riparius larvae on the basis of experimental results and modelling
The aims of this study were to determine depuration rates for a range of per- and polyfluoroalkyl substances (PFASs) using Chironomus riparius, and to test a concentration-dependency hypothesis for the long-chain perfluorotridecanoic acid (PFTrDA) for this species. Midge larvae were exposed to field sediments collected downstream of a fluorotelomer plant, and to the same sediment spiked with PFTrDA. Elimination kinetics results indicated complete elimination of all PFASs by chironomids after 42 h. These data were used to develop two PFTrDA bioaccumulation models accounting for chironomid growth and for compound concentration dependency or not. There was much better agreement between observed and simulated data under the concentration-dependency hypothesis than under the alternative one (passive diffusion). The PFTrDA uptake rate derived from the concentration-dependency model equaled 0.013 ± 0.008 goc gww h−1, and the depuration rate 0.032 ± 0.009 h−1.
(Ecotoxicology and Environmental Safety. vol. 149, n° 0147-6513, pp. 284-290, 28/04/2026)
IRSTEA, EPFL, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, INERIS, ECOSYS, INRA
Réflexions sur deux pendentifs à “dent de requin” trouvés à Burdigala (Bordeaux)
(Aquitania, n° 0758-9670, pp. 357-364, 28/04/2026)
UBM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Omens of coupled model biases in the CMIP5 AMIP simulations
Despite decades of efforts and improvements in the representation of processes as well as in model resolution, current global climate models still suffer from a set of important, systematic biases in sea surface temperature (SST), not much different from the previous generation of climate models. Many studies have looked at errors in the wind field, cloud representation or oceanic upwelling in coupled models to explain the SST errors. In this paper we highlight the relationship between latent heat flux (LH) biases in forced atmospheric simulations and the SST biases models develop in coupled mode, at the scale of the entire intertropical domain. By analyzing 22 pairs of forced atmospheric and coupled ocean-atmosphere simulations from the CMIP5 database, we show a systematic, negative correlation between the spatial patterns of these two biases. This link between forced and coupled bias patterns is also confirmed by two sets of dedicated sensitivity experiments with the IPSL-CM5A-LR model. The analysis of the sources of the atmospheric LH bias pattern reveals that the near-surface wind speed bias dominates the zonal structure of the LH bias and that the near-surface relative humidity dominates the east–west contrasts.
(Climate Dynamics. vol. 51, n° 0930-7575, pp. 2927–2941, 28/04/2026)
LMD, INSU - CNRS, X, IP Paris, ENPC, SU, CNRS, ENS-PSL, PSL, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, MERMAID, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Photodegradation of novel oral anticoagulants under sunlight irradiation in aqueous matrices
Kinetics of photodegradation of novel oral anticoagulants dabigatran, rivaroxaban, and apixaban were studied under simulated solar light irradiation in purified, mineral, and river waters. Dabigatran and rivaroxaban underwent direct photolysis with polychromatic quantum yields of 2.2 × 10−4 and 4.4 × 10−2, respectively. The direct photodegradation of apixaban was not observed after 19 h of irradiation. Kinetics of degradation of rivaroxaban was not impacted by the nature of the aqueous matrix while photosensitization from nitrate ions was observed for dabigatran and apixaban dissolved in a mineral water. The photosensitized reactions were limited in the tested river water (Isle River, Périgueux, France) certainly due to the hydroxyl radical scavenging effect of the dissolved organic matter. The study of photoproduct structures allowed to identify two compounds for dabigatran. One of them is the 4-aminobenzamidine while the second one is a cyclization product. In the case of rivaroxaban, as studied by very high field NMR, only one photoproduct was observed i.e. a photoisomer. Finally, seven photoproducts were clearly identified from the degradation of apixaban under simulated solar light.
(Chemosphere. vol. 193, n° 0045-6535, pp. 329-336, 28/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CBMN, UB, ENITAB, INC-CNRS, CNRS, INERIS, UR MALY, IRSTEA
Observation and numerical modeling of tidal dune dynamics
Tidal sand dune dynamics is observed for two tidal cycles in the Arcachon tidal inlet, southwest France. An array of instruments is deployed to measure bathymetric and current variations along dune profiles. Based on the measurements, dune crest horizontal and vertical displacements are quantified and show important dynamics in phase with tidal currents. We observed superimposed ripples on the dune stoss side and front, migrating and changing polarity as tidal currents reverse. A 2D RANS numerical model is used to simulate the morphodynamic evolution of a flat non-cohesive sand bed submitted to a tidal current. The model reproduces the bed evolution until a field of sand bedforms is obtained that are comparable with observed superimposed ripples in terms of geometrical dimensions and dynamics. The model is then applied to simulate the dynamics of a field of large sand dunes of similar size as the dunes observed in situ. In both cases, simulation results compare well with measurements qualitatively and quantitatively. This research allows for a better understanding of tidal sand dune and superimposed ripple morphodynamics and opens new perspectives for the use of numerical models to predict their evolution.
(Ocean Dynamics. vol. 68, n° 1616-7341, pp. 589-602, 28/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Towards the Development of a Storm Erosion EWS for the French Aquitaine Coast
Towards the development of a storm erosion EWS for the French Aquitanian coast. The 230-km long Aquitaine sandy coast, SW France, is vulnerable to erosion hazards owing to its full exposure to Atlantic storm waves. Since 2015, the Observatory of the Aquitaine Coast and several academic and local partners have developed a network to better survey and forecast storm-driven morphological changes at regional scale. This paper presents the implementation of an early warning system (EWS) with the primary objective to alert the network members 2-3 days ahead in order to perform pre-storm and post-storm surveys. Regional bulletins are edited to identify the most exposed coastal sections. At local scale, tests are realized on two morphological indicators used to forecast qualitatively and quantitatively the likelihood of beach and dune erosion. The two indicators (namely the Collision Regime Indicator, CRI, and the Eroded Volume Indicator, EVI, were calibrated and further validated at two nearby beaches where extensive morphological data are collected regularly: bimonthly surveys from 2009 to 2015 at Truc Vert beach and surveys every 2 to 7 days during the winters since 2015 at Biscarrosse beach. Results indicate promising performance, with the CRI predicting collision regime when front dune erosion was indeed observed, and the EVI predicting fairly accurate eroded sediment volume on cross shore beach profile. Nevertheless, more extensive validation of the CRI and EVI is needed to extend the indicators to the entire Aquitaine coast and for a wide range single storms and storm clusters.
(Journal of Coastal Research. vol. SI 85, n° 0749-0208, pp. 5 p., 28/04/2026)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS