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Tara Polaris expeditions: Sustained decadal observations of the coupled Arctic system in rapid transition
No full textThe coupled Arctic system is in rapid transition and is set to undergo further dramatic changes over the coming decades. These changes will lead most likely to an ice-free ocean in summer, expected before mid-century. The Arctic will become more strongly influenced by atmospheric and oceanographic processes characteristic of mid-latitudes, increasing the prevalence of contaminants and new biological species. This ongoing transition of the Arctic to a new state necessitates systematic monitoring of all sentinels (variables that make an essential contribution to characterizing the Earth's state) to improve our understanding of the system, enhance forecasting and support knowledge-based decisions. Here, we describe a sustained multi-decadal observation program to be implemented on the Tara Polar Station between 2026 and 2046. The monitoring program is designed as a series of year-long drift expeditions, called Tara Polaris, in the central Arctic Ocean, covering all seasons. The multidisciplinary data will bridge ecological, geochemical, biological, and physical parameters and processes in the atmosphere, sea ice and ocean. In addition, data collected with consistent methodologies over a 20-year period will make it possible to distinguish long-term trends from seasonal and interannual variability. In this paper, we discuss specific measurement challenges in each compartment (i.e., atmosphere, sea ice and ocean) along key sentinels and the most pressing scientific questions to be addressed. The expected outcomes of the Tara Polaris program will enable us to understand and quantify the main feedbacks of the coupled Arctic system, with their seasonal and interannual trends and spatial variability.</div
Microplastic impacts on soil and sediment bioturbation: insights from microcosm experiments across diverse ecosystems
No full textInternational audienceEcosystem engineering by bioturbation shapes ecosystems by physically modifying soil and sediment habitats, affecting microbial communities and biogeochemical processes. Although bioturbation is a key process for ecosystem health and functioning, its response to contaminants like microplastics (MPs) remains poorly explored. To address this gap, we conducted three microcosm experiments across terrestrial, freshwater, and marine ecosystems, using three species of ecosystem engineers: Aporrectodea caliginosa (earthworm), Tubifex tubifex (freshwater worm), and Hediste diversicolor (marine worm). Each ecosystem was contaminated by a mixture of polystyrene and polyamide MP fragments and fibers, ranging from 10 to 1000 μm, at two MP concentrations: 0 and 100 mg kg− 1 soil/sediment dry weight. Tracer particles (luminophores) were used to quantify soil/sediment reworking activities of ecosystem engineers. After 21 days of exposure, distinct bioturbation proxies (i.e., maximum penetration depth, surface reworking, particle displacement coefficient, cast production, biodiffusion-like and non-local reworking coefficients) were measured in each microcosm experiment. Our results demonstrated contrasted effects of MPs on bioturbation across ecosystems/ecosystem engineer species. In the terrestrial ecosystem, surface sediment reworking by earthworms remained unaffected by MP contamination although the cast production by A. caliginosa tended to increase (+26 %) with MP contamination. Conversely, in the freshwater ecosystem, the presence of MPs significantly reduced bioturbation activity of tubificid worms, resulting in a nearly fourfold decrease in particle displacement and a substantial reduction in maximum penetration depth of the luminophores. In the marine system, although H. diversicolor maintained effective particle reworking activities with MP contamination, gallery-biodiffusion activity tended to decrease in presence of MPs. Overall, the impact of MP contamination on bioturbation process was context-dependent. It can be hypothesized that the impact of MPs on bioturbation process was dependent on the size of the ecosystem engineering species, with the strongest effect observed on the smallest organism (T. tubifex)
In vitro production of (+)-catechin and (−)-epicatechin glucuronides to better understand the in vivo metabolism of a polyphenol-rich extract (Memophenol™)
No full textInternational audienceConsumption of (+)-catechin and (−)-epicatechin is associated with beneficial effects on human health. However, their limited systemic circulation in native form suggests that their metabolites may contribute to these effects. The aim of this study was to produce and structurally characterize glucuronide metabolites of (+)-catechin and (−)-epicatechin, which are not commercially available, and to assess their presence in plasma from volunteers who consumed a blend of grape and wild blueberry extracts. Firstly, four monoglucuronides of each flavanol were produced using rat liver microsomes and characterized by UHPLC-DAD-MS/MS and NMR. Using these compounds, we were able to confirm the presence in human plasma of three glucuronides: one known (−)-epicatechin glucuronide and two previously unidentified (+)-catechin glucuronides. Further research is needed to understand their biological role
Electron paramagnetic resonance (EPR) spin trapping applied to Chardonnay wines: impact of phenolic content and ethanol
No full textInternational audienceChemical oxidation is the main cause of damage during the bottle aging of white wines. It is due to Fenton-type reaction mechanisms, i.e., a radical oxidation cascade which leads to the formation of 1-hydroxyethyl radicals (1-HER) from ethanol. An optimized electron paramagnetic resonance (EPR) approach, using the Fenton reaction and N-tert-Butyl-α-(4-pyridyl-1-oxide) nitrone as spin trap, was used to study the formation kinetic of 1-HER. Important parameters of the reaction were identified and optimized, i.e., temperature, dissolved oxygen and free bisulfite content. We found that acetaldehyde removed bisulfite without artifacts on 1-HER kinetics, making the protocol suitable for routine laboratory analysis. We then validated the log-normal model to describe the complex formation/degradation kinetic of 1-HER and used it to rank 69 Chardonnay wines in four categories. Low levels of phenolic acid, in particular the cinnamic acids such as caftaric acid, seemed to correspond to a specific formation kinetic of 1-HER (high level produced slowly). In addition, ethanol concentration (0-100 % vol.) greatly impacted its formation kinetics, whereas it had non-significant effect within the white wine range (12-15 % vol.). These results demonstrate that the response of white wines to radical oxidation in controlled and tuned conditions is a promising approach to evaluate aging potential and suggest that maturity level might modulate the 1-HER formation in Chardonnay wines.</div
NRT-GSF: A novel near-real-time ground-satellite fusion algorithm to retrieve daily green area index at field scale
No full textInternational audienceNear-real-time (NRT) daily crop monitoring at the field scale is crucial for precision agriculture, yet remains challenging due to limitations in the spatial or temporal resolution of existing remote sensing methods. While Sentinel-2 provides adequate spatial resolution for field-level applications, its temporal resolution is insufficient for capturing rapid crop dynamics, especially in cloudy regions. Existing spatiotemporal fusion techniques require multiple clear-sky images and lack true NRT capability, while ground-based sensors offer continuous monitoring but with limited spatial coverage. To address these limitations, this study develops the Near-Real-Time Ground-Satellite Fusion (NRT-GSF) algorithm, a novel approach based on a Bayesian dynamic linear model and Kalman filtering. The algorithm uniquely integrates Sentinel-2 imagery with continuous measurements from Internet of Things for Agriculture (IoTA) systems to generate daily 10-m Green Area Index (GAI) products. Its recursive framework supports both forward prediction in NRT mode following satellite overpasses and backward updating to refine historical profiles. Implemented over French wheat fields using 34 IoTA systems and Sentinel-2 time series from 2019, the algorithm effectively enhanced spatiotemporal completeness and accuracy (R = 0.75–0.98, RMSE = 0.1–0.49). A comprehensive leave-one-out Sentinel-2 evaluation demonstrated its superiority over the current Consistent Adjustment of the Climatology to Actual Observations (CACAO) algorithm. Ground validation using handheld RGB cameras further confirmed the accuracy of the GAI products from the new algorithm (RMSE = 0.5). The NRT-GSF framework offers a robust and operationally solution for daily, high-resolution crop GAI mapping in NRT mode, and it can be extended to other traits or applications in the near-real-time context
Artificial selection of suppressive or conducive rhizosphere microbiota circumvents the growth-defense trade-off due to a foliar pathogen
No full textInternational audiencePlant-pathogen interactions are influenced by physiological responses and rhizospheric microorganisms, which can create disease-suppressive or disease-conducive soils affecting pathogen dynamics. This study used artificial selection to shape soil microbiota conditioned by Arabidopsis thaliana to either suppress or promote the foliar pathogen Pseudomonas syringae DC3000 (Pst). Over successive iterations, plants were inoculated with Pst, and soils were selected based on plant symptoms: enhanced resistance (suppressive), increased susceptibility (conducive), or no selection (control). A non-inoculated group (non-conditioned) was also included. Disease symptoms, Pst proliferation, and rhizosphere microbiota were monitored each iteration. Selection for suppressive soils reduced disease severity and Pst levels, while conducive soils showed the opposite. Each soil type was enriched in distinct bacterial communities. A growth-defense trade-off was evident in control soils but less so in selected soils. Gene expression analysis revealed that plant hormone homeostasis, especially salicylic acid (SA) and jasmonic acid (JA) played key roles with SA linked to local defense and JA to systemic responses. This work highlights artificial selection as a promising strategy to modulate soil microbiota, influencing plant-pathogen interactions and microbial dynamics
Feeding a persistent laying hen: Effect of dietary amino acid levels in rearing and dietary energy source and level in laying on body composition and metabolism
No full textInternational audienceThe level and source of dietary protein and energy provided during rearing and laying might influence body composition and metabolic functions of laying hens. We therefore studied the influence of a low or high Apparent Fecal Digestible (AFD) Lys level in all rearing diets and constant or reduced ME level and source during laying (Reducing Energy over time with High Oil = REHO; Constant Energy High Oil = CE; Reducing Energy over time with Low Oil = RELO) on body composition and metabolism in a 2 x 3 factorial design. Dekalb White pullets were randomly divided over 8 pens per treatment and housed until 110 wk of age. Body composition (relative breast, abdominal fat pad and liver weights and total body chemical composition of crude fat, CP, ash and moisture) and liver crude fat levels were measured 4 times during rearing and at 8 wk intervals during laying. Plasma metabolic markers (triglyceride, free fatty acids) were measured 5 times and adipokines 3 times during laying. Data were subjected to mixed model analyses. Hens fed RELO compared to REHO diets had elevated plasma free fatty acid and triglyceride levels in some weeks, heavier relative liver weights with higher liver crude fat levels in most sampled timepoints, indicating de novo lipoprotein synthesis. Segmented regression models showed that relatively less body fat was directed towards abdominal fat in hens fed RELO diets, with a greater proportion accumulating in other fat depots, such as the liver. Correlations showed that hens with higher relative abdominal fat pad weights between wk 52 and 84 had lower ADFI and FCR in wk 52 to 110. This indicates abdominal fat is needed to supply sufficient ME in the final phases of laying. Higher plasma chemerin levels correlated to a lower BW, egg weight, abdominal fat deposition but higher liver crude fat levels. Adiponectin showed opposite effects. Feeding REHO diets indicated better fat utilization to support egg production in longterm producing hens
Access to agricultural lands influences the effects of seasonal drought on early growth and juvenile body mass in a large herbivore
No full textInternational audienceIncreasing rainfall deficits threaten the persistence of terrestrial large herbivores, yet, very few studies have investigated the effects of droughts on populations inhabiting anthropized areas, which dominate European landscapes. We investigated how rainfall deficits (measured using the Standardized Precipitation Index, SPI) and local agricultural land use shaped the early growth of fawns and the body mass that they attained by their first winter in a population of European roe deer (Capreolus capreolus) in southwestern France. Using data on 155 new-born fawns, we found that early growth decreased as local woodland availability increased, irrespective of spring rainfall conditions. In contrast, based on data from 218 GPS-monitored juveniles, aged 8-10 months, we found that local landscape composition and seasonal rainfall deficits had interacting effects on winter body mass. The juveniles were generally heavier with higher proportions of meadows in their predicted home range (mean 0.4 kg +/- 0.2 SE), but this difference disappeared following dry summers (SPI < 1). Juveniles with low access to summer crops (e.g., 5%) were significantly lighter following dry autumns (mean -0.9 kg +/- 0.3 SE), whereas this was not the case for those with higher access to these crops (e.g., 20%). Although populations of large herbivores may respond to harsh climatic conditions by exploiting anthropogenic resources, our results suggest that any compensation effects are strongly dependent on the type of anthropogenic land use and the timing of rainfall deficits, calling for explicitly considering how local climatic conditions and human practices may interact in shaping individual performance and, so, population dynamics
Du serment doctoral d'intégrité scientifique à un serment personnel : un atelier d'écriture et de réflexion sur la responsabilité et le rôle des scientifiques dans la société
No full textNous présentons un atelier de réflexion sur le serment doctoral d’intégrité scientifique et d’écriture d’un serment personnel, destiné aux doctorantes et doctorants, et plus généralement au personnel de la recherche. L’atelier est proposé depuis 2025 comme formation à l’éthique de la recherche dans quelques écoles doctorales en France. Avec un dispositif original, il permet d’examiner plusieurs aspects de la pratique et des enjeux sociaux-environnementaux de le Recherche : la responsabilité des scientifiques, l’engagement, le rôle des sciences dans l’anthropocène, la place de l’éthique et de l’intégrité dans la pratique du doctorat et des sciences en général
Biofouling in milli-labyrinth channels of drip irrigation systems using reclaimed wastewater: A review of optical methods and numerical modelling
No full textInternational audienceDrip irrigation systems are known for their high water-use efficiency due to the combination of using milli-labyrinth channels to optimise flow distribution and reusing reclaimed wastewater. However, clogging andbiofouling remain significant challenges that affect system performance and lifespan. This review provides acomprehensive overview of biofouling in drip irrigation systems, with a focus on how hydrodynamic conditionsand nutrient availability in reclaimed wastewater influence the attachment, growth, detachment, and decayof biofilm. The ability of advanced optical techniques, including particle tracking velocimetry, industrialcomputed tomography, and optical coherence tomography to visualise, measure, and analyse biofoulingprocesses in drip irrigation systems is discussed, along with their strengths and limitations. Additionally, theability of current biofilm modelling approaches, including both continuum and discrete methods, to simulatenutrient transport, microbial activity, and biofilm–fluid interactions are discussed. By combining insights fromexperimental data and computational models, this review also identifies key research gaps and presents a newframework for applying biofilm modelling to drip irrigation systems. Future research directions are suggestedto improve our understanding of drip irrigation biofouling and to predict it, to optimise emitter design, andincrease the overall reliability and sustainability of drip irrigation system