Approche bayésienne pour estimer les paramètres d'un modèle biodynamique chez les invertébrés benthiques d'eau douce
Les modèles biodynamiques classiques ont été validés pour formaliser la variabilité de la bioaccumulation de contaminants par différentes espèces d'organismes. La bioaccumulation est alors décrite comme la résultante des processus d'absorption et d'élimination (Luoma et Rainbow, 2005). Chez les invertébrés benthiques, ces modèles ont été développés à l'origine pour les métaux, puis pour quelques contaminants organiques, en considérant l'organisme comme un compartiment unique et en ne prenant en compte généralement qu'une seule voie d'exposition. Toutefois, il est crucial de tenir compte dans de tels modèles de tous les processus impliqués dans la bioaccumulation de contaminants, tels que différentes voies d'absorption et notamment la voie trophique, la croissance de l'organisme, mais aussi les effets de saturation et/ou de biotransformation. Ces phénomènes sont d'autant plus importants à prendre en compte pour les invertébrés benthiques, dans la mesure où ils jouent un rôle clé dans le transfert des contaminants puisqu'ils se situent souvent à la base des réseaux trophiques aquatiques. Par ailleurs, l'estimation des paramètres de ces modèles est couramment effectuée par une approche fréquentiste, en deux étapes : premièrement en estimant les paramètres liés à l'élimination, et dans un second temps l'estimation des paramètres liés à l'absorption. Cette méthode nécessite la plupart du temps de fixer certains paramètres lorsque tous ne peuvent pas être estimés simultanément, induisant un biais puisqu'il n'est pas exclu que ces paramètres soient corrélés. L'inférence Bayésienne permet (i) de pallier le problème d'estimation simultanée de tous les paramètres d'un modèle à partir de données de nature différente ; (ii) d'utiliser l'information disponible sur les paramètres (à partir de la littérature, d'expériences préliminaires ou d'avis d'experts) ; et (iii) de fournir une estimation des incertitudes à travers les distributions a posteriori de chaque paramètre, issue de la distribution jointe de tous les paramètres estimés simultanément (incluant donc la corrélation éventuelle). L'objectif de cette étude est de développer un cadre Bayésien générique pour estimer simultanément les paramètres d'un modèle biodynamique chez des espèces d'invertébrés aquatiques variées exposées à divers contaminants, si possible peu connus ou émergents. La distribution a posteriori obtenue pour tous les paramètres permettra une évaluation plus précise de l'incertitude de la bioaccumulation. Nous illustrons cette approche avec des données expérimentales obtenues en conditions contrôlées de cinétiques d'accumulation et d'élimination chez Gammarus fossarum et Chironomus riparius exposés à des sédiments ou des feuilles contaminées en PCB 153 ou en hexabromocyclododécane (retardateur de flamme).
(pp. 20, 19/10/2026)
IRSTEA, LBBE, UCBL, VAS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Ocean as the main driver of Antarctic ice sheet retreat during the Holocene
Ocean-driven basal melting has been shown to be the main ablation process responsible for the recession of many Antarctic ice shelves and marine-terminating glaciers over the last decades. However, much less is known about the drivers of ice shelf melt prior to the short instrumental era. Based on diatom oxygen isotope (δ18Odiatom; a proxy for glacial ice discharge in solid or liquid form) records from western Antarctic Peninsula (West Antarctica) and Adélie Land (East Antarctica), higher ocean temperatures were suggested to have been the main driver of enhanced ice melt during the Early-to-Mid Holocene while atmosphere temperatures were proposed to have been the main driver during the Late Holocene. Here, we present a new Holocene δ18Odiatom record from Prydz Bay, East Antarctica, also suggesting an increase in glacial ice discharge since ~4500 years before present (~4.5 kyr BP) as previously observed in Antarctic Peninsula and Adélie Land. Similar results from three different regions around Antarctica thus suggest common driving mechanisms. Combining marine and ice core records along with new transient accelerated simulations from the IPSL-CM5A-LR climate model, we rule out changes in air temperatures during the last ~4.5 kyr as the main driver of enhanced glacial ice discharge. Conversely, our simulations evidence the potential for significant warmer subsurface waters in the Southern Ocean during the last 6 kyr in response to enhanced summer insolation south of 60°S and enhanced upwelling of Circumpolar Deep Water towards the Antarctic shelf. We conclude that ice front and basal melting may have played a dominant role in glacial discharge during the Late Holocene.
(Global and Planetary Change. vol. 166, n° 0921-8181, pp. 62-74, 19/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CERFACS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GLACCIOS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, IACT, CSIC, UGR, UCL-ASTR, UCLouvain, MERMAID, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
The balance of canopy and soil effects determines intraspecific differences in foundation species’ effects on associated plants
The impact of plant–plant interactions on species diversity patterns has been broadly addressed in stressful environments, such as alpine ecosystems, where foundation species promote species richness by creating habitat for other species. However, foundation species with contrasting phenotypes might modify the microhabitat differently, which would alter the subordinate community composition, and coincide with distinct feedback effects of those subordinate species on the foundation species. However, the precise interaction mechanisms that facilitate species are not fully understood, especially the relative contribution of above- and below-ground compartments of foundation species to subordinate species and the potential feedbacks they receive. We explored whether two contrasted canopy phenotypes (tight and loose) of the shrub Cytisus galianoi differed in their effects on the microhabitat and on subordinate plant community composition in a dry subalpine system. We also experimentally distinguished the relative contribution of above- (canopy) and below-ground (soil) effects of C. galianoi on the most frequent subordinate species, Festuca indigesta, as well as the reciprocal effects of F. indigesta on C. galianoi. We performed observational and manipulative experiments to assess the influence of phenotypic differences of the shrub on understorey microhabitat and subordinate plant community composition. Reciprocal effects were assessed by removing either F. indigesta from the understorey of the two shrub phenotypes or the C. galianoi canopy from the immediate vicinity of F. indigesta. The two C. galianoi phenotypes differed in mean values of functional traits (like stem density or plant height), modified their understorey microhabitats differently and hosted distinct subordinate communities. Loose phenotypes had more positive effects on community composition and diversity than tight phenotypes. In addition, tight phenotypes simultaneously showed both more positive above-ground and more negative below-ground effects on F. indigesta than loose phenotypes. There were no significant feedback effects of F. indigesta on C. galianoi. The two phenotypes of the foundation species C. galianoi showed contrasting effects on the subordinate plant community: Compared to the tight phenotype, the loose phenotype had higher associated species diversity and reduced reciprocal interaction intensities above- and below-ground with the subordinate species F. indigesta. This highlights the impact of phenotypic variation for plant interactions and community-level diversity.
(Functional Ecology. vol. 32, n° 0269-8463, pp. 2253-2263, 19/10/2026)
EEZA, CSIC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Geoarchaeology of the Roman port-city of Ostia: Fluvio-coastal mobility, urban development and resilience
Ostia is one of the most extensively excavated cities of the Roman period. The port-city of Rome, which today lies 4 km from the coastline, was established in a very constrained environment at the mouth of the River Tiber. Based on a review of the geoarchaeological and archaeological research at Ostia, 4 new cores analysed through palaeoenvionmental methods, and 21 new radiocarbon dates, we propose a new model of the fluvio-coastal landscape of Ostia from its origin: (1) the coastline shifted rapidly westward between the 8th and the 6th c. BCE followed by a slow progradation and possible erosion phases until the end of the 1st c. CE; (2) the castrum of Ostia (c. late 4th–early 3rd c. BCE) was founded away from the river mouth but close to the River Tiber; (3) between the 4th and the 1st c. BCE, the River Tiber shifted from a position next to the castrum, below the northern Imperial cardo of Ostia, to 150 m to the north; (4) a possible harbour was established to the north of the castrum during the Republican period; (5) the city expanded and a district was built over the harbour and the palaeochannel between the Republican period and the beginning of the 2nd c. CE, showing that Ostia was a dynamic and resilient city during that time. Finally, we suggest the possibility to combine urban fabric analysis (the orientation of the structures) and palaeoenvironmental analysis for reconstructing the evolution of the city in relation to the fluvio-coastal mobility.
(Earth-Science Reviews, n° 0012-8252, pp. 265-283, 19/10/2026)
LIVE, UNISTRA, CNRS, Archéorient, UL2, CNRS, ULiège, IGAG, CNR, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, INP, CEPAM, UNS, CNRS, BSR
Gestion et valorisation des carottes sédimentaires à but scientifique en France : vers un système intégré
Les carottes sédimentaires font l'objet d'un intérêt grandissant de la part des paléo-environnementalistes mais également d’écologues qui s'intéressent à la trajectoire des écosystèmes (Pansu et al., 2015; Perga et al., 2015). Les carottes marines ou continentales prélevées dans le cadre de consortiums internationaux (IODP, ICDP) donnent l’exemple depuis des décennies en terme de partage d’échantillons pour ce type d’étude ; plus récemment l’augmentation de ré-études massives de données publiées (Bolliet et al., 2016; Cartapan is et al., 2016) démontrent la valeur de ces échantillons et des données associées. De leur côté depuis quelques années, les législateurs et financeurs poussent à l’ouverture, au partage et à la traçabilité des données : on peut citer l’OCDE, l’UE, l’ERC... Comment notre communauté peut-elle s’inscrire au quotidien dans ces processus qui demandent de profonds changements culturels dans nos pratiques de recherche ? C’est pour tenter d’apporter une réponse à cette question que nous avons cherché à développer un système intégré de captation et de gestion des métadonnées des échantillons issus de forages scientifiques, qui puisse être implémenté au niveau national et connecté à des initiatives internationales, sur lequel pourront venir s’appuyer les futurs Plans de Gestion de Données. Par une approche bottom-up, pragmatique et au plus près des pratiques des équipes de recherche, nombreuses, dispersées, aux moyens inégaux, et en s’appuyant sur des initiatives existantes, nous tentons de répondre petit à petit à différents niveaux - de la mission de prélèvement jusqu'à leur stockage, en passant par la mise à disposition, le suivi et la valorisation des échantillons et des métadonnées qui leur sont associées. Des avancées rapides ont pu être obtenues par la rencontre entre une communauté de paléoécologues et des équipes techniques novatrices dans le domaine du partage et de l’interopérabilité mêlant des informaticiens, géomaticiens, curateurs d’échantillons et de données. Cette dynamique s’appuie sur 3 projets nationaux (Cyber-Carothèque nationale s/c Equipex CLIMCOR ANR-11-EQPX-0009 ; QR-Code LTSER- France ; ROZA LTSER-France) et s’inscrit dans le cadre du Centre de Carottage et de Forage National (C2FN), une cellule de la division technique de l’INSU. Nous présenterons dans cette intervention 4 outils qui seront à court terme interconnectés : i)CoreBOOK, une application mobile de terrain dédiée à la captation des métadonnées de forage ; ii) le portail de la cyber-carothèque national, un hub accueillant les données nouvellement acquises et les inventaires de carothèques ; iii) Collec-Science, outil générique de gestion de collections d’échantillons naturels adapté à nos besoins (s/c projet QrCODE); enfin iv) ROZA (Rétro-Observatoire des Zones Ateliers), un prototype de découvreur et visualiseur de données destiné à favoriser la réutilisation des échantillons et des données paléoenvironnementales en mettant à disposition les données essentielles à la capitalisation des connaissances d’études successives sur un même site. Les perspectives aujourd'hui sont grandes, le système modulaire qui commence à se dessiner doit permettre à chacun de trouver son compte, à son rythme, où opérationnel peut enfin rimer avec standardisation, traçabilité et interopérabilité tout en conservant une utilisabilité au plus proche des activités et besoins quotidiens des chercheurs et personnels d’accompagnement, afin d’opérer un virage en douceur vers des pratiques de la science dite « ouverte
(19/10/2026)
EDYTEM, USMB [Université de Savoie] [Université de Chambéry], CNRS, Fédération OSUG, DTI, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMD, INSU - CNRS, X, IP Paris, ENPC, SU, CNRS, ENS-PSL, PSL, OASU, UB, INSU - CNRS, ULR, CNRS, INRAE, LCE, CNRS, UMLP, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GEDI, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GRESE, UNILIM, DYNAFOR, INRA, ENSAT, INP-ENSAT, AgroToulouse, INP-AgroToulouse, Toulouse INP, Comue de Toulouse, Toulouse INP, Comue de Toulouse, LEHNA IPE, LEHNA, UCBL, ENTPE, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, UR EABX, IRSTEA, LETG - Brest, LETG, UNICAEN, NU, UA, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN, GEOTRAC, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GLACCIOS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
Seasonal variations of contamination and exoskeletal malformations in the white shrimps Palaemon longirostris in the Gironde estuary, France
Since the end of the 1980s, white shrimps (Palaemon longirostris) from the Gironde estuary have exhibited exoskeletal malformations, mainly involving cephalothorax, rostrum, scaphocerites and uropods. An 8-month study was carried out in 2015. Each month, 200 individuals were sampled and examined for exoskeletal malformations. Temporal variations in malformationfrequency were noted,particularlyduringthebreedingperiod, along withdecreases in the sizeof non-deformedshrimps related to the appearance of juveniles in breeding sites, and high mortality among deformed shrimps. A significant increase in proportions of deformed shrimp was observed, relating particularly to the size (and therefore the age) of individuals. No significant difference was found between shrimp proportions with different numbers of malformations (one to four) for a fixed size class, nor was there any variation in proportions within different size classes for a fixed number of malformations. This would appear toindicate thatthe number ofmalformations isacquiredand new malformations donot seemto appearduringthe lifecycle,exceptforthesmallest(youngest)shrimps.Themalformationspectrumshowednosignificantdifferencesbetweenthe biggest and smallest individuals for the different malformation associations, except for those involving cephalothorax, rostrum and uropods. This would suggest that some malformation associations lead to a higher mortality rate in shrimps subjected to them, due to greater impairment of feeding and/or swimming behaviour. Multiple component analysis of the different types of malformation showed correlations between exoskeletal pieces (rostrum and cephalothorax) and appendixes (scaphocerites and uropods). Regarding metal contamination in shrimp, no significant difference was highlighted between deformed and nondeformed shrimps. Organic pollutants were not measured in tissues. Certain herbicides such as metolachlore and chlortoluron.
(Environmental Science and Pollution Research. vol. 25, n° 0944-1344, pp. 22689-22701, 19/10/2026)
UR EABX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Modifications physiques du littoral
(pp. 305-329, 19/10/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SIAME, UPPA, LIENSs, INSU - CNRS, ULR, CNRS, UR ETBX, IRSTEA
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, 19/10/2026)
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, 19/10/2026)
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
Interaction of freshwater diatom with gold nanoparticles: adsorption, assimilation, and stabilization by cell exometabolites
The rising concern about the potential toxicity of synthetic gold nanoparticles (AuNPs) in aquatic environments requires a rigorous estimation of physico-chemical parameters of reactions between AuNPs and major freshwater microorganisms. This study addresses the interaction of 10-nm size, positively charged AuNPs with periphytic freshwater diatoms (Eolimna minima). The adsorption experiments on viable cells were performed in 10 mM NaCl and 5 mM NaCl + 5 mM NaHCO3 solution at a variable pH (3–10), at an AuNPs concentration from 1 µg/L to 10,000 µg/L, and an exposure time from a few minutes to 55 days. Three types of experiments, adsorption as a function of time (kinetics), pH-dependent adsorption edge, and constant-pH “Langmuirian” type isotherms, were conducted. In addition, long-term interactions (days to weeks) of live diatoms (under light and in the darkness) were performed. The adsorption was maximal at a pH from 3 to 6 and sizably decreased at a pH of 6 to 10. Results of adsorption experiments were modeled using a second order kinetic model, a Linear Programming Model, Freundlich isotherm, and a ligand binding equation for one site competition. The adsorption of AuNPs(+) most likely occurred on negatively-charged surface sites of diatom cell walls such as carboxylates or phosphorylates, similar to previously studied metal cations. Under light exposure, the AuNPs were stabilized in aqueous solution in the presence of live cells, probably due to the production of exometabolites by diatoms. The adsorbed amount of AuNPs decreased after several days of reaction, suggesting some AuNPs desorption. In the darkness, the adsorption and assimilation were stronger than under light. Overall, the behavior of positively charged AuNPs at the diatom–aqueous solution interface is similar to that of metal cations, but the affinity of aqueous AuNPs to cell exometabolites is higher, which leads to the stabilization of nanoparticles in solution in the presence of diatoms and their exudates. During photosynthetic activity and the pH rising above 9 in the vicinity of diatom cells, the adsorption of AuNPs strongly decreases, which indicates a decreasing potential toxicity of AuNPs for photosynthesizing cells. The present study demonstrates the efficiency of a thermodynamic and kinetic approach for understanding gold nanoparticles interaction with aquatic freshwater peryphytic microorganisms.
(Minerals. vol. 8, n° 2075-163X, pp. 99, 19/10/2026)
IOCAG, ULPGC, GET, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, TSU, FECIAR UrB RAS, RAS, IPGG SB RAS, SB RAS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ICMCB, UB, INC-CNRS, CNRS