Organotropism and biomarker response in oyster Crassostrea gigas exposed to platinum in seawater
Platinum (Pt) is a technology critical element (TCE) for which biogeochemical cycles are still poorly understood. This lack of knowledge includes Pt effects on marine organisms, which proved to be able to bioconcentrate this trace element. Oysters Crassostrea gigas were exposed to stable Pt isotope spiked daily in seawater for 35 days. Seawater was renewed daily and spiked (with Pt(IV)) to three nominal Pt concentrations (50, 100, and 10,000 ng L−1) for two replicate series. Organotropism study revealed that gills, and to a lesser extent mantle, are the key organs regarding Pt accumulation, although a time- and concentration-dependent linear increase in Pt levels occurred in all the organs investigated (i.e., digestive gland, gonads, gills, mantle, and muscle). In oysters exposed to Pt concentrations of 10,000 ng L−1, significant biomarker impairments occurred, especially at cellular levels. They reflect altered lipofuscin and neutral lipid contents, as well as intralysosomal metal accumulation. These observations were attributed to activation of excretion/detoxification mechanisms, including Pt elimination through feces and clearly support the importance of the digestive gland in the response to direct Pt exposure. Despite relatively constant condition index, the integrative biological response (IBR) index suggests a generally decreasing health status of oysters
(Environmental Science and Pollution Research. vol. 27, n° 0944-1344, pp. 3584-3599, 02/09/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UPV / EHU
Foraminiferal community response to seasonal anoxia in Lake Grevelingen (the Netherlands)
Over the last decades, hypoxia in marine coastal environments has become more and more widespread, prolonged and intense. Hypoxic events have large consequences for the functioning of benthic ecosystems. In severe cases, they may lead to complete anoxia and the presence of toxic sulfides in the sediment and bottom-water, thereby strongly affecting biological compartments of benthic marine ecosystems. Within these ecosystems, benthic foraminifera show a high diversity of ecological responses, with a wide range of adaptive life strategies. Some species are particularly resistant to hypoxia-anoxia, and consequently it is interesting to study the whole foraminiferal community as well as species-specific responses to such events. Here we investigated the temporal dynamics of living benthic foraminiferal communities (recognised by CellTracker™ Green) at two sites in the saltwater Lake Grevelingen in the Netherlands. These sites are subject to seasonal anoxia with different durations and are characterised by the presence of free sulfide (H 2 S) in the uppermost part of the sediment. Our results indicate that foraminiferal communities are impacted by the presence of H 2 S in their habitat, with a stronger response in the case of longer exposure times. At the deepest site (34 m), in summer 2012, 1 to 2 months of anoxia and free H 2 S in the surface sediment resulted in an almost complete disappearance of the foraminiferal community. Conversely, at the shallower site (23 m), where the duration of anoxia and free H 2 S was shorter (1 month or less), a dense foraminiferal community was found throughout the year except for a short period after the stressful event. Interestingly, at both sites, the foraminiferal community showed a delayed response to the onset of anoxia and free H 2 S, suggesting that the combination of anoxia and free H 2 S does not lead to increased mortality , but rather to strongly decreased reproduction rates. At the deepest site, where highly stressful conditions prevailed for 1 to 2 months, the recovery time of the community takes about half a year. In Lake Grevelingen, Elphidium selseyense and Elphidium magellanicum are much less affected by anoxia and free H 2 S than Ammonia sp. T6. We hypothesise that this is not due to a higher tolerance for H 2 S, but rather related to the seasonal availability of food sources, which could have been less suitable for Ammonia sp. T6 than for the elphidiids.
(Biogeosciences. vol. 17, n° 1726-4170, pp. 1415-1435, 02/09/2026)
LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, NIOZ
Quasagro - Gestion agronomique des sols et des résidus : quels impacts sur la qualité sanitaire des productions végétales de grande culture ?
En relation avec la qualité sanitaire des produits de la récolte, le projet Quasagro visait à valider des éléments de gestion globale des risques multicontaminants (mycotoxines, éléments-traces métalliques et résidus de pesticides) associés aux facteurs environnementaux et aux pratiques agronomiques en grandes cultures (blé tendre, blé dur et tournesol) par analyse multifactorielle : effets pédoclimatiques, résidus de culture, intrants et apports de matière organique. Il s’est appuyé sur le réseau national de parcelles Quasaprove, renforcé par des essais plein champ existants. Par une approche sans a priori, des modèles statistiques ont été testés sur le blé tendre, à partir de paramètres pédologiques ou climatiques. Aucun modèle ne s’est révélé suffisamment prédictif. Nous avons également cherché si certaines pratiques entraînaient des différences de concentration dans les végétaux. Il est apparu qu’il n’y a pas de différence entre les parcelles labourées et non labourées, en fonction du type de fertilisation, ou en fonction du précédent ou de l’usage d’un CIPAN. Aucune différence n’est apparue non plus entre les parcelles conduites en agriculture biologique ou en agriculture conventionnelle. Quelle que soit la culture, l'équilibre est déterminé par le type de fertilisation. Dans le cas de la fertilisation uniquement azotée (ammonitrate), le bilan est toujours négatif. Dans le cas de la fertilisation organique en agriculture biologique, le bilan est toujours positif et le sol accumule les éléments-traces. Dans le cas de l'agriculture conventionnelle avec fertilisation NPK, le bilan est positif pour l'arsenic, le cadmium et le plomb, et négatif pour le cuivre et le zinc. L’exportation des pailles, qui génère un flux d’exportation relativement faible, ne change pas ces conclusions. Sur les parcelles étudiées, les niveaux de concentration cumulés observés s’échelonnent du sub-ng/g à la centaine de ng/g (ps) dans les sols. Les concentrations cumulées maximales en agriculture biologique sont de l’ordre de la dizaine de ng/g. Par comparaison des itinéraires techniques conventionnel/biologique, les herbicides sont présents de façon marquée en conventionnel et quasi absents en biologique ; les fongicides sont présents en biologique à des concentrations supérieures aux limites de quantification et les niveaux de fongicides sont relativement similaires en biologique et en conventionnel dit raisonné. La présence notable de pesticides rémanents (e.g. époxiconazole dont les derniers traitements dataient de plusieurs années) a également été mise en évidence. Le devenir des pesticides dans l’environnement est conditionné par leur comportement dans les sols. L’interaction entre divers processus régissant leur devenir (rétention, dégradation, transfert) va conditionner entre autres leur persistance (ou rémanence). Plus particulièrement, les processus de dégradation des pesticides contribuent à diminuer cette persistance. Le potentiel de biodégradation microbienne dépend ainsi des molécules (toxicité intrinsèque, capacité d’adsorption au sol), de facteurs pédoclimatiques (type d’argiles, matière organique, température et humidité), de facteurs microbiens tels que la biomasse globale et la présence de micro-organismes adaptés à certaines molécules (ex: isoproturon, 2,4-D) et des historiques de traitement (fréquence de traitement). D’une manière générale, il semble que les systèmes bas intrants favorisent l’activité microbienne des sols, par rapport aux systèmes conventionnels.
(Innovations Agronomiques. vol. 79, n° 1958-5853, pp. 121-146, 02/09/2026)
Acta, UMR ISPA, Bordeaux Sciences Agro, INRAE, ECOSYS, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, MycSA, INRAE, ITAB, ARVALIS
A 14-Year Multi-sites and High-Frequency Monitoring of Salinity in the Tidal Garonne River (S-W France) Reveals Marked Inter-annual Variability in Marine Intrusion
With its 625 km2, the Gironde estuary (S-W France) is one of the largest European estuaries. The tidal Garonne and Dordogne Rivers, whose confluence is located at about 75 km from the mouth, form its fluvial section. The Tidal Garonne River (TGR) represents about 2/3 of the freshwater inputs to the Gironde. For a long time it has been accepted the limit of saline intrusion, identified by a salinity higher than 0.5, was nearly at the confluence. In the last decades, there has been a significant decrease of the annual mean TGR discharge, likely to influence marine intrusion. It is often difficult to establish changes in marine intrusion in estuaries due to the limited available data set. This work presents the interest of a multi-sites and high frequency monitoring system, called MAGEST, that records since 2004 four physico-chemical parameters, including salinity, to establish a reference database of water-quality of this large fluvio-estuarine system, in order to address current and future water-quality issues, including saline intrusion. This work presents in details the 14-year time series of salinity along the Garonne-Gironde continuum. Not surprisingly, there are large differences among the instrumented stations depending on their localization. High-frequency salinity chronic at Bordeaux is used to assess the occurrence of saline intrusion in the Tidal Garonne River, revealing marked inter-annual variability in marine intrusion depending of fluvial discharge. The ongoing regional changes suggest an increase of salinity in TGR in the next decades.
(pp. 3-11, 02/09/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Ecological succession and resilience of plankton recovering from an acute disturbance in freshwater marshes
The increase in extreme events such as storms is one of the major threats that coastal ecosystems will have to face in the near future. In such a context, both maturation and ecological successions processes remain at the core of ecology to better anticipate the changes to ecosystem biodiversity and functions facing environmental stressors. However, these concepts are mainly approached through closed experimental studies that oversimplify the mechanisms. A survey was carried out on a ‘natural’ and open ecosystem subjected to an acute disturbance, i.e. a marine submersion of freshwater drained marshes, occurring after a storm. Plankton biomass, production and taxonomic/functional phytoplankton diversity were followed weekly at four stations over 2 months. Most of the stations were disrupted by this acute disturbance and displayed gradual growth and development, as described in the classical maturation process. The main differences between stations were attributed to the heterogeneity of the communities before the storm, the intensity of the disturbance and the different human actions performed to recover the freshwater environment. The concept of ‘ecological resilience’ was thus better suited than ‘engineering resilience’ for such open systems facing constant fluctuations in environmental drivers. With regard to ecological succession, the more impacted stations were marked by a significant change in taxonomic beta-diversity, with numerous stochastic processes, due to taxa dispersion. They first exhibited a convergence in functional traits due to the increase in nutrient availability drained from the catchment basin and then an increase in divergence when nutrients became limited.
(Science of the Total Environment. vol. 709, n° 0048-9697, pp. 135997, 02/09/2026)
LIENSs, INSU - CNRS, ULR, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNIMA, DIACT
Sensitivity to cadmium of the endangered freshwater pearl mussel Margaritifera margaritifera from the Dronne River (France): experimental exposure
Margaritifera margaritifera is a critically endangered species in Europe. Among the causes explaining its decline, metal pollution had never been deeply studied. Thus, an ecotoxicological investigation was developed on this species which comes from the Dronne River (South-West of France). Cadmium (Cd) exposure of mussels at 2 and 5 μg/L for 7 days was conducted to test their vulnerability to this metal, and also the potential endocrine disruption power of Cd. Morphometric analyses, gonad histological observations, metal bioaccumulation, metallothionein (MTs) production, measures of malondialdehyde (MDA), and finally quantitative relative expression analysis of genes involved in various metabolic functions were performed. The main results showed Cd accumulation increasing in a dose-dependent manner, especially in the gills. The same trend was observed for gene expression relative to oxidative stress. Histological analysis of the gonads highlighted a predominance of hermaphrodite individuals, but after 7 days of exposure to Cd, the percentage of female was largely increased compared with controls, from 17 to 33%. These results demonstrate the endocrine disruption effect of Cd on freshwater pearl mussels.
(Environmental Science and Pollution Research. vol. 27, n° 0944-1344, pp. 3715-3725, 02/09/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Positive associations among rare species and their persistence in ecological assemblages
According to the competitive exclusion principle, species with low competitive abilities should be excluded by more efficient competitors; yet, they generally remain as rare species. Here, we describe the positive and negative spatial association networks of 326 disparate assemblages, showing a general organization pattern that simultaneously supports the primacy of competition and the persistence of rare species. Abundant species monopolize negative associations in about 90% of the assemblages. On the other hand, rare species are mostly involved in positive associations, forming small network modules. Simulations suggest that positive interactions among rare species and microhabitat preferences are the most probable mechanisms underpinning this pattern and rare species persistence. The consistent results across taxa and geography suggest a general explanation for the maintenance of biodiversity in competitive environments.
(Nature Ecology & Evolution. vol. 4, n° 2397-334X, pp. 40-45, 02/09/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Hydroclimate change in subtropical South Africa during the mid-Piacenzian Warm Period
The mid-Piacenzian Warm Period (mPWP, 3.264–3.025 Ma) of the Pliocene epoch has been proposed as an analog for future climate scenarios. Disagreement between the paleoenvironmental reconstruction and model simulations of the climate in subtropical regions for this period suggests that more investigation of the subtropical climate variability of the mPWP is needed. This study presents pollen, microcharcoal and benthic foraminifera oxygen isotope records generated from marine sediment cores of International Ocean Discovery Program (IODP) Exp. 361 Site U1479 from the Cape Basin offshore of South Africa for the period between 3.337 and 2.875 Ma. With an average sample resolution of 3 ka, this record represents the highest-resolution record of mPWP vegetation change from the region. Our results indicate that the vegetation during the mPWP was dominated by fynbos (species-rich heathy vegetation in the Cape Floristic Region) with variable proportions of Ericaceae. Moreover, the development of the Afrotemperate forest (tall, multilayered indigenous forests in South Africa) reflects shifts in the amounts of precipitation between winter and summer in the year-round rainfall zone. The vegetation variation is probably influenced by the latitudinal insolation gradient in response to precession forcing. Several glacials depicted by the benthic foraminifera oxygen isotope record were characterized by lower percentage values of Restionaceae, higher percentage values of ericoid fynbos and Afrotemperate forest. These events correspond well with cooler SE Atlantic sea surface temperatures driven by interactions of both atmospheric and oceanographic processes. The cooler sea surface temperatures attributed to Antarctic ice sheet expansion, reduced Agulhas leakage (heat and salt transfer from the Indian Ocean to the Atlantic Ocean) and/or intensified southern Benguela upwelling, resulted in less precipitation in the winter rainfall zone of South Africa.
(Quaternary Science Reviews. vol. 249, n° 0277-3791, pp. 106643, 02/09/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Acute Toxicity of Sodium Chloride, Nitrates, Ortho-Phosphates, Cadmium, Arsenic and Aluminum for Juveniles of the Freshwater Pearl Mussel: Margaritifera Margaritifera (L.1758)
The freshwater pearl mussel (FWPM) Margaritifera margaritifera (L.1758) is critically endangered in Europe and ecotoxicological studies on the species are scares. Here, 96 h acute toxicity tests were conducted at 16 °C with sodium chloride (NaCl), nitrates (NO3−), ortho-phosphates (PO43−), cadmium (Cd), aluminum (Al) and arsenic (As) on 13- to 28-month-old post-parasitic juveniles. The experimental protocol was developed according to conditions described in a standard guide and was modified in order to assess toxicity thresholds for the Dronne River. Results showed that juveniles were tolerant to concentrations of Al, Cd, As, PO43−, NO3− and NaCl, largely higher than those found in the Dronne river, since 96 h EC50s (effective concentrations) were >954 µg/L for Al; >110 µg/L for Cd; >127 µg/L for As; >5.01 mg/L for PO43−; between 1000 and 1500 mg/L for NO3− and were 1.19 and 1.33 g/L for NaCl. Moreover, the use of a substrate in experiments was found not to affect juvenile responses and younger juveniles seemed more sensitive than older individuals. This study thus provides new data about the tolerance of FWPM to environmental pollution and suggests that pollutant concentrations in the river are significantly lower than levels affecting them.
(Environments. vol. 7, n° 2076-3298, pp. 48, 02/09/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
AquaVIT Quand les plantes aquatiques invasives transcendent les frontières : approche pluridisciplinaire des relations entre espèces, milieux et gestionnaires
Le projet de recherche AquaVIT vise à accompagner l’évolution des modalités de gestion des grands lacs aquitains, confrontés à des enjeux environnementaux liés à la colonisation par les plantes aquatiques invasives. Ces plantes exotiques à caractère envahissant peuvent occuper une place importante au sein des écosystèmes lacustres et, par la même occasion, entraver de nombreux usages des lacs, notamment la pratique d’activités de loisirs. En Nouvelle-Aquitaine, ces macrophytes invasifs font l’objet d’une attention de la part des gestionnaires, élus et scientifiques depuis maintenant plus de trente ans. Néanmoins, un certain nombre d’interrogations demeurent. Les plantes présentent encore des dynamiques de colonisation importantes dans de nombreux plans d’eau et les opérations de gestion visant à les réguler sont menées localement. Le projet de recherche AquaVIT s’intéresse particulièrement aux questions suivantes : - Les plantes invasives constituent-elles un élément perturbateur du bon fonctionnement écologique lacustre ? - Comment "faire avec" les plantes au quotidien ? - Comment "faire ensemble" ? Le projet AquaVIT affiche une ambition pluridisciplinaire forte, qui associe, dès sa conception, les sciences humaines et sociales d’une part, et les sciences biogéochimiques et écologiques d’autre part. Ce projet propose une alternative à la vision quantitative et mesurable, strictement centrée sur la plante (i.e distribution et biomasse des plantes), vers une approche plus qualitative, orientée sur les relations entre la plante et son environnement, celui-ci étant considéré d’un point de vue écosystémique et social. Appropriée par chacune des disciplines, cette posture a donné lieu à des approches empiriques diverses et spécifiques. Dans le projet AquaVIT ont été déployées, entre autres, des enquêtes (qualitatives et quantitatives) auprès des acteurs, des études sociohistoriques basées sur des analyses de documents, mais aussi des prélèvements et mesures biologiques et physico-chimiques in situ, ainsi que des expérimentations en laboratoire. Le croisement de ces regards et de ces méthodes constitue une des richesses du projet. Les résultats obtenus invitent à s’éloigner d’une représentation univoque des conséquences potentielles de la présence d’herbiers denses de plantes aquatiques invasives, tout comme à contextualiser la problématique socio-environnementale de leur gestion. Ceci peut être illustré par le fait que les processus écologiques et biogéochimiques à l’œuvre dans les herbiers sont étroitement liés aux conditions hydrodynamiques locales, ou encore que les représentations et les attitudes à leur sujet dépendent pour partie des usages et des pratiques de terrain. Dans certaines conditions, une telle « contextualisation » de la problématique a favorisé l’émergence d’innovations organisationnelles, se traduisant, par exemple, par des dispositifs à caractère participatif. En dépit des motivations et des intentions à s’engager, dont témoignent les usagers des plans d’eau, les soutiens (humains, techniques et financiers) des pouvoirs publics, restent essentiels. Sur un plan spatial, ces innovations peinent toutefois à dépasser l’échelle des sites, de sorte que la mise en relation entre plusieurs secteurs, que l’on est parfois en mesure d’attendre compte tenu de la dynamique des plantes et des processus, repose encore très largement sur les réseaux sociotechniques des gestionnaires traditionnels des milieux, et peu sur les utilisateurs finaux.
(pp. 125 p., 02/09/2026)
UR EABX, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR ETBX, INRAE