HAL-Université de Bretagne Occidentale
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Culturable macroplastic-associated potential human pathogens in coral reef lagoons, Madagascar
No full textInternational audiencePotentially human pathogenic bacteria (PHPBs) have been detected in plastic-associated marine microbiomes, primarily through DNA-based methods. However, data on their culturability and concentrations on plastics remain limited, yet are essential to assess actual health risks. To address this gap, 70 floating macroplastic and 20 seawater samples were collected from two human-impacted reef lagoons in southwestern Madagascar (AtsimoAndrefana region). PHPBs were cultured from their microbiomes using selective media and quantified. Macroplastics were predominantly polypropylene (34 %) and polyamide (31 %). In increasing order of concentration, four culturable PHPBs, Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, and Vibrio Harveyi clade species, were identified on both macroplastics and in seawater, across all sites and polymer types. Notably, 52 % of macroplastic samples harbored two PHPB species simultaneously, while only 7 % were PHPB-free. Concentrations of all PHPBs were consistently and significantly higher on macroplastics than in seawater, regardless of the measurement unit or polymer type, with the Vibrio Harveyi clade being the most abundant. No significant correlations were observed among PHPB species concentrations, suggesting limited interaction and independent colonization. These findings indicate that floating macroplastics may serve as reservoirs and fomites for viable PHPBs. However, their potential impacts on ecosystems and human health should be interpreted cautiously. We emphasize the need to contextualize PHPB concentration data by considering factors such as exposure pathways, environmental persistence, and bacterial virulence, rather than relying solely on concentration-based comparisons, which may lead to misinterpretatio
Domoic acid production by a Pseudo-nitzschia australis strain under zinc and copper exposure
No full textInternational audienceThe diatom species Pseudo-nitzschia australis can produce domoic acid (DA), a neurotoxin- responsible for amnesic shellfish poisoning. Copper (Cu) and zinc (Zn) are essential trace metals for marine phytoplankton, but they can become either limiting or toxic at pico- to subnanomolar ionic concentrations—levels that are can be reached in coastal ecosystems. The effect of exposure to these metals on DA production remains unclear for Cu and is largely unknown for Zn. In this study, we investigated the effects of toxic picomolar concentrations of Cu²⁺ and four non-limiting concentrations of Zn²⁺ on the metabolism and physiology of a toxic P. australis strain isolated from the coastal waters of North Biscay (France). Using principal component analysis, we observed changes in cell populations over time depending on metal exposure. Cu²⁺ toxicity was marked by a 35 % decrease in maximum cell density and a reduction in growth rate (µ₊Cu = 0.55 µₐₓ). DA production was differentially modulated by the two metals: toxic Cu²⁺ levels stimulated DA synthesis (+200 %), while elevated Zn²⁺ bioavailability significantly decreased it (by up to –85 %), including when Zn²⁺ was combined with toxic levels of Cu²⁺ (–65 %). We further discuss DA production by P. australis as a potential protective mechanism against oxidative stress. Additional data on intracellular glutathione (GSH) quotas—an important reactive oxygen species (ROS) scavenger and Cu²⁺ chelator— are presented and linked to Zn2+ bioavailability. GSH cell quotas were significantly correlated with DA production (p < 0.05) further supporting existing links between metal exposition, oxydative stress and DA production. This study suggests that ambient concentrations of Cu²⁺ and Zn²⁺ are critical factors regulating DA production in coastal marine systems
On the tropical nature of an intense Mediterranean cyclone in the ocean-atmosphere system
No full textInternational audienceThe Mediterranean basin hosts a large number of cyclones every year. Among them, some rare cases named medicanes present similarities with tropical cyclones but their dynamical characteristics are debated. The ocean-atmosphere dynamics of Medicane Ianos (2020) are studied here through km-scale fully coupled ocean-wave-atmosphere simulations. These allow investigating the tropical nature of Ianos in terms of both atmospheric circulation and thermal structure, and of oceanic cold wake response which feedbacks negatively onto the cyclone's intensity. Simulations match in situ and remotely sensed observations in the ocean and atmosphere well. Three life cycle phases can be distinguished with a mature phase during which the cyclone is compact and axisymmetric. Orographic acceleration is shown to induce asymmetry in the cyclonic winds and precipitation prior to landfall. These are expected to be common for medicanes given the small scale and steep orography of the Mediterranean basin. Ianos distinguishes itself from previous medicanes by its intense cold wake wherein the sea surface cooling exceeds 3\textdegree{C}. The wake results mainly from mixing at the base of the mixed layer, while surface fluxes play a secondary role as revealed by temperature budget analysis. The amplitude and dynamics of the wake are alike those found in tropical cyclones of category 2 or more. A deep warm core cyclonic eddy on Ianos' track is responsible for an interruption in the cold wake which coincides with the re-intensification of the cyclone during its mature phase. Such eddies are widespread in the Mediterranean but poorly constrained in models
Development and external validation of a FDG PET-based radiomics model predicting occult lymph node metastasis in non-small cell lung cancer patients
No full textInternational audiencePurpose/Objective(s) Accurate detection of occult lymph node metastasis (OLNM) in patients with localized non-small cell lung cancer (NSCLC) remains a clinical challenge. This study aimed to develop and validate a radiomics-based predictive model for OLNM. Materials/Methods A radiomics model (Model PET ) and a model (Model Combined ) combining radiomics and clinical features were developed using a retrospective monocentric cohort of localized NSCLC patients treated with surgery (Cohort A) and tested on an external cohort (Cohort B) of 112 localized NSCLC patients also treated with surgery (publicly available Radiogenomics cohort). The model was further assessed in an independent cohort of 488 patients with localized NSCLC who underwent definitive stereotactic body radiotherapy (SBRT) (Cohort C) using regional relapse free survival (RRFS) as a surrogate for OLNM. Radiomic features were extracted from pre-treatment FDG PET and combined to predict OLNM using a multilayer perceptron approach. Results In the training cohort, the Model PET and Model Combined achieved AUCs of 0.92/0.99 and balanced accuracies (Bacc) of 80.0%/85.3%, respectively. In the Cohort B, the Model PET and Model Combined resulted in AUCs of 0.73/0.67 and Baccs of 71.2%/51.7%, respectively. In the Cohort C, the predicted OLNM risk based on Model PET was significantly associated with worse RFFS (HR 1.60 95% CI 1.03-2.48, p = 0.04). The Model Combined was not associated with survival outcomes (p > 0.05). Conclusion This study presents a radiomics-based predictive model for OLNM in localized NSCLC, validated across several retrospective independent cohorts. Subject to a prospective evaluation, the model could be used to refine clinical decision-making
Analysis on workforce availability, education and training needs for medical physics experts to ensure quality and safety of medical applications involving ionising radiation in the EU – Status and recommendations from the EU-REST project
No full textInternational audiencePurpose The European Union Radiation, Education, Staffing & Training (EU-REST) study aimed to assess workforce availability and identify education and training needs related to the medical use of ionising radiation. The study also sought to develop guidelines on staffing and education/training for key professional groups, including Medical Physics Experts (MPEs), responsible for ensuring radiation safety and quality of medical radiation practice across the EU. Methods A survey was conducted to collect data about workforce availability, and education/training across the EU, as well as a literature review encompassing national, European, and international guidelines. Draft guidelines and recommendations were submitted for peer review and stakeholder consultation for assessment and identification of potential barriers to implementation. Results The survey revealed considerable variability in staffing and education/training across the EU, as well as a widespread lack of reliable data. The study highlights the need to reinforce the role of MPE as the qualified professional for advising and taking responsibility in matters related to radiation physics and radiation protection applied to medical exposures. Establishing national workforce registries, harmonising training standards, ensuring professional recognition, and mandating CPD are strategic recommendations for strengthening the MPE profession in response to emerging technological and regulatory demands. These represent essential steps toward a sustainable, competent, and mobile MPEs workforce across Europe. Conclusion The EU-REST project echoes the European Commission’s call for further harmonisation of the MPEs role across Member States, in accordance with the Basic Safety Standards Directive, and provides targeted recommendations to facilitate its consistent implementation throughout the EU. © 2026 Associazione Italiana di Fisica Medica e Sanitaria
Fine-scale fishery patterns reveal challenges and opportunities for coastal management and conservation in Madagascar
No full textInternational audienceThe blue economy agenda has generated tensions over marine space use, often marginalising small-scale fisheries in development policies. Boat tracking technology has only recently begun to be applied in these fisheries, but it offers a promising approach to accurately map fishing distribution. In this study, we explored how environmental, technological, and social factors influenced fishers’ spatial behaviour and catches at sea in one of the Madagascar's most heavily exploited coral reef fisheries. We recorded boat movements at 30 s intervals and reef fish catches simultaneously during a 12-month participatory survey. The spatial distribution of annual fishing effort (h·ha −1 ) and fish catch rates (kg·ha −1 ) was characterised by fishing community and gear type (beach seine, mosquito net trawl, gillnet, handline, and speargun) at 250−m resolution. A total of 75 reef fish families were recorded in catches (1,466 t·yr −1 ) across approximately 218 km 2 . Annual catch rates of the seven dominant families (comprising 62% of total catches) were highly variable and heterogeneous (mostly 1–391 kg·ha −1 ) across marine habitats. A total of 7,359 tracks by 521 boats were recorded. Fishing pressure was highly variable spatially (mostly 1−150 h·ha −1 ) among communities and gear types. The results revealed preferential target areas, informal marine tenure, limited travel distance to fishing grounds, and overexploitation patterns within the fishery, offering critical insights for fishery management and inclusive marine spatial planning. This study showed the usefulness and opportunities of deploying combined boat tracking and catch surveys in small-scale fisheries through participatory research
Transferts sédimentaires et de pesticides associés en contexte viticole : retours sur le projet PULSE
No full textInternational audienceL’érosion du sol et la pollution de l’eau par les pesticides sont des questions investiguées depuis longtemps dans les espaces agricoles. Les études portant sur le sujet ont fait le constat de l’ampleur du phénomène mais aussi de la complexité des transferts, liée à l’organisation spatiale des paysages (Le Bissonnais et al., 2002 ; Reulier, 2015). L’analyse de la structure paysagère et de ses évolutions permet donc de mieux comprendre l’organisation des processus mais aussi d’identifier les leviers d’action pour limiter les transferts (Catalogne et Le Hénaff, 2017 ; Fressard et Cossart, 2019). Dans ce cadre, le projet PULSE avait pour objectifs de progresser dans la compréhension de la dynamique des transferts sédimentaires et de pesticides associés dans le Beaujolais viticole (2020-2023). Il a reposé sur une démarche mixte, alliant mesure des flux sur le terrain et analyse spatiale / modélisation pour rendre compte du rôle de la structure paysagère dans les transferts. Pour donner des clefs de compréhension de l’organisation de la cascade sédimentaire et pour appréhender l’effet du changement d’échelle dans les transferts, les analyses ont porté sur trois échelles emboîtées : de la parcelle au bassin versant d’une centaine de km². Ce travail a permis de documenter la dynamique sédimentaire et de pesticides associés. Il en ressort des transferts sédimentaires cohérents avec la dynamique observée en contexte agricole et des taux de transferts de pesticides associés aux particules de sol conséquents. L’analyse de la structure paysagère à mis en avant l’importance de prendre en compte l’exhaustivité des éléments du paysage pour faire le lien avec les mesures de terrain, et de comparer différents scénarios d’évolution des paysages. À l’avenir, il s’agira notamment de creuser l’approche de modélisation prospective pour mieux prendre en compte les évolutions liées aux facteurs climatiques et anthropiques, à différentes échelles. BibliographieCatalogne C. & Le Hénaff G., 2017 – Guide d'aide à l'implantation des zones tampons pour l'atténuation des transferts de contaminants d'origine agricole. Elaboré dans le cadre du groupe technique "Intégration des zones tampons dans la gestion des bassins versants", Irstea-ONEMA, 68.Le Bissonnais Y., Thorette J., Bardet C. & Daroussin J., 2002 – L’érosion hydrique des sols en france.Fressard M. & Cossart É., 2019 – A graph theory tool for assessing structural sediment connectivity: Development and application in the Mercurey vineyards (France). Science of the Total Environment, 651, 2566 2584.Reulier R., 2015 – Structure paysagère et dynamiques spatiales des transferts hydro-sédimentaires. Approche par simulation multi-agents. Thèse de doctorat. Université de Caen Normandie
Experimental characterisation of breaking wave impact loads on a vertical cylinder
No full textInternational audienceThis article presents experimental measurements of breaking wave impact loads on a vertical cylinder. The focus is on the influence of some of the breaking wave properties on the measured force. These properties are the distance to breaking, δ, defined as the distance between the breaking location and the front face of the cylinder, and the breaking strength, characterised here by the Γ parameter proposed by Derakhti et al. (J. Fluid Mech., 2018, vol. 848, p. R2). The wave characteristics are obtained through numerical simulations of the breaking waves using a fully nonlinear potential flow solver. Seven breaking waves with different breaking strengths have been considered. For each wave, the distance to breaking has been systematically varied and the resulting impact force time-history was measured. It is found that except for the two less intense breaking cases, corresponding to values of Γ lower than one, there is a value of δ for which the magnitude of the impact force is maximum. Small variations of the distance to breaking δ strongly influence the impact force time-history and its maximum. A linear relationship is observed between the maximum force and the breaking strength Γ . For the wave cases with values of Γ higher than one, the maximum impact force is observed when the distance to breaking δ is close to 5 % of the wavelengt
An inquiry into Search Engine Neutrality: the case of movements against police violence in France and the U.S.
No full textInternational audienceThe digital transformation has revolutionized information consumption, with search engines playing a pivotal role in shaping user access to diverse media. Employing algorithms, these engines influence content visibility and aggregate news sources, significantly molding public opinion. As gatekeepers of information, search engines impact media outlet visibility, affecting online traffic, revenue, and journalistic diversity. In breaking news and societal issues, search engines expedite information dissemination, influencing initial narratives. Understanding their role is crucial for transparency and user access to diverse information. Focusing on movements against police violence, our paper conducts a comparative analysis across 12 search engines for terms "Black Lives Matter" and "Justice pour Adama". Our innovative methodology identifies biases in information diversity, providing insights into the dynamics shaping visibility of societal issues.</div