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Decline and status of natural pearl oyster (Pinctada margaritifera) stocks in two French Polynesia black pearl farming lagoons
No full textInternational audienceIn French Polynesia, the pearl oyster Pinctada margaritifera has allowed black pearl production since four decades. The production remains dependent on spat collections in atoll lagoons. Through their reproduction, the oysters of the natural stock are contributors of spats, and possibly the only contributor. After an assessment in 2013, natural stocks of Takaroa and Ahe atolls were revisited in 2022 and 2024 respectively. Results show a sharp decrease of the densities at almost all field sites, with average lagoon-wide losses by factors of 2.35 and 8.87 for Ahe and Takaroa respectively. Takaroa was impacted in 2013–2014 by a massive harmful phytoplanktonic bloom and the decrease was expected, but the population size structure shows recruitment, providing hope for farmers. Conversely, the reason for Ahe's population decline remains unclear. Likely suspects are increased periods of high temperature and predation that affect oysters at their different life stages and impact recruitment and survival
Quelle place pour le plurilinguisme et les approches plurielles au sein des curricula des Master FLE en France ?
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Sooty terns as large-scale bioindicator of mercury contamination in marine ecosystems: A pantropical approach
No full textInternational audienceMercury (Hg) is a toxic contaminant, which poses serious threats to both wildlife and humans worldwide. Although tropical oceans receive half of the world’s atmospheric Hg depositions, its biomonitoring is largely overlooked in these ecosystems. This study provides a comprehensive, pantropical assessment of Hg contamination of marine ecosystems, using the sooty tern (Onychoprion fuscatus) as bioindicator. Total Hg concentrations were measured from feathers collected in 28 colonies across all tropical oceans (2003–2022), from adults (n =564) and chicks (n =407), to evaluate longer- and shorter-term contamination. To investigate the role of bird trophic ecology on Hg contamination, bulk stable isotopes of carbon (δ13C) and nitrogen (δ15N) were also analysed, as respective proxies for feeding habitat and diet. Because baselines of stable isotopes may vary at large spatial scales, compound-specific nitrogen stable isotope analyses of amino-acids were performed on a subset of adults (n =91, 19 colonies), to calculate their trophic position (TP), accounting for both baseline and trophic effects. As expected, Hg concentrations were higher in adults than chicks, because of their shorteraccumulation period. Overall, colonies from the Northern Hemisphere exhibited the highest Hg concentrations, consistently with higher historical anthropogenic emissions of Hg in the North. Models revealed that Hg contamination was driven by environmental contamination (colony location, feeding habitat) rather than diet (TP), which remained similar across the pantropical range. Our findings provide important baseline data for tropical marine ecosystems and underscore the need for enhanced monitoring in regions, where gold-mining and changing oceanographic conditions will likely modify future Hg exposure
Comparative Analysis of Urinary Electrolyte Profiles among Populations in Grand Sido and Kouh-Est in Southern Chad
No full textInternational audienceUrinary electrolytes play a key role in assessing hydration status, metabolism and renal function. This study aims to characterise and quantify the major urinary electrolytes (Na⁺, K⁺, Ca²⁺, Cl⁻) in two rural areas of southern Chad: Grand Sido and Kouh-Est. Urine samples were collected and analysed according to rigorous biochemical protocols. The results reveal significant disparities between the two areas, highlighting the influence of dietary habits, access to drinking water and environmental conditions. These data provide an important basis for the implementation of targeted public health and nutrition strategies. This is a cross-sectional, descriptive, and analytical study conducted among 783 volunteer participants aged 5 to 90 years residing in the localities of Grand Sido and Kouh-Est. Morning urine samples were collected under aseptic conditions and then transported to the laboratory in accordance with storage conditions. Urinary concentrations of sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), and chloride (Cl⁻) were determined using standardized biochemical methods (colorimetric methods). Statistical analysis was used to compare electrolyte profiles between the two areas and according to age groups, with a significance threshold set at p < 0.05. This study highlights significant differences in urinary electrolyte profiles between Grand Sido and Kouh-Est, reflecting the influence of nutritional factors, access to drinking water, and local environmental conditions. The results obtained provide a useful reference for monitoring hydration status and renal function in these rural populations. They can also guide the development of prevention, nutrition, and public health strategies tailored to the context of southern Chad
Elimination du manganèse par une lagune construite pour le traitement passif d'une eau de mine : Facteurs environnementaux et communautés microbiennes
No full textInternational audienceManganese (Mn) removal in passive mine water treatment remains a challenge due to its slow oxidation kinetics,requiring specific biogeochemical conditions. Constructed wetlands are often the key functional units enablingMn removal in full-scale passive treatment plants. This study examines the key biogeochemical factors influencing Mn removal in a full-scale passive mine water treatment plant located in Al`es (South-East France). Overone year, monitoring of physicochemical parameters, microbial communities, and Mn speciation in solid phaseswas conducted every two months. Results highlight temporal variations in Mn removal efficiency, with two mainmechanisms identified: (1) Mn carbonate (MnCO₃) precipitation, likely influenced by high carbonate concentrations in mine water, and (2) Mn oxide (δ-MnO₂) formation, mainly associated with reed rhizosphere, where itaccumulates as mineral plaque. In mine water, Mn removal correlates with Fe particle concentrations, suggestinga catalytic effect, as well as with alkalinity and the abundance of microorganisms affiliated to Alteromonadaceae,suggesting a microbial influence. Mn removal appears to be primarily abiotic, driven by favourable pH andalkaline conditions that promote Mn carbonate precipitation, by autocatalytic oxidation reactions occurring onrhizosphere surfaces and by plant’s design including surface area and hydrological conditions. Microbial communities may facilitate certain Mn removal processes depending on environmental conditions.L'élimination du manganèse (Mn) dans le traitement passif des eaux de mine reste un défi en raison de sa cinétique d'oxydation lente, nécessitant des conditions biogéochimiques spécifiques pour atteindre une élimination efficace. Cette étude examine les principaux facteurs biogéochimiques influençant l'élimination du Mn dans une station de traitement passif des eaux de mine à grande échelle située à Alès (Sud-Est de la France). Pendant un an, le suivi des paramètres physico-chimiques, des communautés microbiennes et de la spéciation du Mn dans les phases solides a été effectué tous les deux mois. Les résultats mettent en évidence des variations saisonnières de l'efficacité d'élimination du Mn, avec l'identification de deux principaux mécanismes : (1) la précipitation du carbonate de Mn (MnCO3), probablement influencée par la forte concentration en carbonates dans les eaux de mine, et (2) la formation d'oxyde de Mn (δ-MnO2), principalement associée au rhizosphère des roseaux, où il s'accumule sous forme de plaque minérale. Dans les eaux de mine, l'élimination du Mn est corrélée avec les concentrations de particules de Fe, suggérant un effet catalytique, ainsi qu'avec l'alcalinité et l'abondance de micro-organismes affiliés à Alteromonadaceae, ce qui suggère une influence microbienne. L'élimination du Mn semble être principalement abiotique, entraînée par un pH favorable et des conditions alcalines qui favorisent la précipitation du carbonate de Mn ainsi que par des réactions d'oxydation autocatalytiques se produisant à la surface de la rhizosphère. Cependant, les communautés microbiennes peuvent faciliter certains processus d'élimination du Mn selon les conditions environnementales. La dynamique saisonnière des communautés microbiennes en réponse aux changements environnementaux peut influencer les mécanismes d'élimination du Mn
Conservacionismo, protesta ambiental y emergencia del ecologismo político en España, del Franquismo a la Democracia (Galicia, Aragón y Andalucía)
No full textInternational audienceThe aim of this article is to provide an approach to the history of environmentalism and to bring new perspectives to the study of Francoism and the Spanish transition by analyzing environmental conflicts on a regional scale. In response to the industrial, energy and urban planning policies of the regime, the main environmental conflicts of the period between 1960 and 1986 have proved to be a perfect historical laboratory for understanding in all their complexity the profound social and political transformations of the period. The methodology employed consists of consulting municipal, regional and national archives, press analyses and subsequently comparing our case studies (Galicia, Aragon and Andalusia). Through in-depth case studies of Aragon, Galicia and Andalusia, we observe the path from popular protest against environmental injustice to the subsequent formalization of an environmentalist political ideology in the 1980s. The article aims to highlight the links between popular environmentalism, social memory and processes of politicisation of the territory during the late Franco era and the TransitionEl objetivo de este artículo es dar un enfoque a la historia del ecologismo y aportar nuevas perspectivas al estudio del franquismo y la transición española, analizando los conflictos ambientales a escala regional. En respuesta a las políticas industriales, energéticas y urbanísticas del régimen, los principales conflictos ambientales del periodo compren-dido entre 1960 y 1986 se han revelado como un laboratorio histórico ideal para comprender en toda su complejidad las profundas transformaciones sociales y políticas del periodo. La metodología empleada consiste en la consulta de archivosmunicipales, regionales y nacionales, análisis de prensa y una posterior comparación en nuestros casos de estudio (Galicia, Aragón y Andalucía). A través de los estudios en profundidad de estos casos de Aragón, Galicia y Andalucía, analizamos el camino desde la protesta popular contra la injusticia ambiental hasta la posterior formalización de una ideología política ecologista en los años ochenta. El artículo pretende poner de relieve los vínculos entre ecologismo popular, memoria social y procesos de politización del territorio durante el tardofranquismo y la Transición
Variable Order Fractional Creep Model of Wood Material: Case of Tropical Pericopsis Elata Species
No full textInternational audienceA rheological model based on the new formulation of fractional calculus with variable order is developed to study the viscoelastic behavior of wood. The model, which uses only two rheological elements, exhibits an enhanced memory effect, demonstrated by a satisfactory fit to the experimental deformations observed in four-point bending tests on Pericopsis elata samples. By determining the parameters of the linear function of the fractional order used, a physical significance emerges that explains the changes occurring within the material during the tests. This type of model, therefore, provides wood engineers with additional information about the behavior of the material under stres
Apprentissage par renforcement profond pour le trading algorithmique multi-actifs : une approche multi-agent basée sur les processus de décision markoviens
No full textInternational audienceThis study proposes a deep reinforcement learning (DRL) approach for algorithmic trading within a multi-agent framework. The trading problem is formulated as a partially observable Markov decision process (POMDP), where each agent interacts with a market environment corresponding to a specific currency pair. To capture temporal dependencies in financial time series, a recurrent neural network (RNN) is combined with a Dueling Double Deep Q-Network (DDDQN). Market states incorporate historical prices and standard technical indicators. An extensive experimental evaluation is conducted on Forex data from Yahoo Finance covering the 2022–2025 period, using a rigorous out-of-sample protocol with baseline strategies and ablation studies. The results indicate that the proposed model achieves superior risk-adjusted performance compared to reference methods, while maintaining improved stability under volatile market conditions.ResuméCette étude propose une approche de trading algorithmique fondée sur l'apprentissage par renforcement profond (Deep Reinforcement Learning, DRL) dans un cadre multi-agent. Le problème de trading est formulé comme un processus de décision markovien partiellement observable (POMDP), dans lequel chaque agent interagit avec un environnement de marché spécifique à une paire de devises. Afin de capturer les dépendances temporelles inhérentes aux séries financières, une architecture à base de réseau de neurones récurrent (RNN) est combinée à un algorithme Dueling Double Deep Q-Network (DDDQN). Les états du marché intègrent des prix historiques ainsi que des indicateurs techniques standards. L'évaluation expérimentale est conduite sur des données Forex issues de Yahoo Finance couvrant la période 2022-2025, selon un protocole hors échantillon rigoureux incluant des stratégies de référence et une étude d'ablation. Les résultats montrent que le modèle proposé surpasse les baselines en termes de rendement ajusté du risque, tout en présentant une meilleure stabilité face à la volatilité du marché.</div
Appréciation de l’entomophagie par les ménages de Kananga
No full textInternational audienceThis study confirms that the majority of surveyed households (94%) consume insects in the city of Kananga, with the most commonly consumed insects being termites and crickets (93% each) according to their consumption frequency. The degree of appreciation, defined as the overall satisfaction level and acceptance of households regarding insect consumption, is rated as very good by most households. This high level of consumption is primarily explained by the availability of insects in the market as well as factors associated with their consumption, such as nutritional and cultural perceptions.Cette étude atteste que la majorité des ménages enquêtés (94%) consomment les insectes dans la Ville de Kananga, avec les insectes les plus consommés (93% chacune) étant les termites et grillons conformément à leurs fréquences de consommation. Le degré d’appréciation, défini comme le niveau de satisfaction globale et d’acceptation des ménages vis-à-vis de la consommation d’insectes, est jugé très bon par la plupart des ménages. Cette forte consommation s'explique principalement par la disponibilité des insectes sur le marché ainsi que par les facteurs associés à leur consommation, tels que les perceptions nutritionnelles et culturelles
Hisser le drapeau palestinien sur un édifice public est-il légal ?
No full textInternational audienceUne question juridique qui varie selon la réponse politiqu