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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 (Atsimo-Andrefana 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 misinterpretation
Charge Transfer Between Ce and Fe During Cooling of an Aluminosilicate Melt: An In Situ XANES Investigation
No full textInternational audienceMultivalent elements are often incorporated to silicate glasses to enhance specific properties to the final product. However, these properties strongly depend on the redox state of the multivalent elements. While the redox behavior of glasses containing a single multivalent element is well studied, research on the in situ interaction between multiple multivalent elements is scarce. In this study, in situ XANES spectroscopy was used to investigate the high temperature redox state of both Ce and Fe in an aluminosilicate melt. The results were compared to room temperature measurements. Our findings demonstrate that, at high temperature equilibrium, Ce and Fe act independently. However, upon cooling below 900°C, a charge transfer process occurs between the two elements as described by the reaction Ce4+ + Fe2+ → Ce3+ + Fe4+. The existence of such a charge transfer, observed even in melts doped with very low Ce and Fe amounts, could suggests that both elements are not randomly distributed in the melt. The intensity of the charge transfer process depends on the CeO2/FeO ratio, with the element present in excess showing minimal change in redox state upon cooling. This explains the difference of room temperature redox state between samples
Platinum and Rare Earth Elements distribution in costal sediments from French western Mediterranean Sea
No full textInternational audienceThis study presents the first assessment of Technological Critical Elements (TCE), specifically platinum (Pt) and rare earth elements (REE), in coastal sediments along the French western Mediterranean Sea. These trace elements, increasingly used in advanced technologies, raise particular concerns due to their potential environmental impact. Surface sediment samples were collected from 21 stations along the French Mediterranean coast (from Spain border to Italy including Corsica Island) to evaluate TCE concentrations and identify potential sources. Most of the REE concentrations fell within expected natural levels and were mainly influenced by the geological characteristics of local watersheds, indicating a dominant geogenic origin. When normalized to European Shale, REE distribution patterns exhibited convex shapes, typical of coastal environments. In contrast, localized Pt enrichment were detected at specific sites, particularly in port areas, which could be linked to anthropogenic emissions from vehicular catalytic converters. These results highlight platinum as a relevant emerging contaminant in urban coastal environments. However, unexpected REE and Pt concentrations at the mouth of the Hérault river call for further investigation. This study highlights the importance of integrating geological background and anthropogenic pressures in coastal sediment quality assessments and supports the inclusion of TCE in long -term environmental monitoring programs in the Mediterranean Sea
Atmospheric specifications for infrasound studies: 2. the added value of a high-top model, UA-ICON
No full textInternational audienceInfrasound monitoring activities that deal with long-range acoustic propagation, as within the Comprehensive Nuclear-Test-Ban Treaty’s (CTBT), need accurate and operational modeling of the atmosphere up to the lower thermosphere. Yet, operational meteorological products issued by weather services are topped at around 80 km altitude with a sponge layer starting in the stratosphere. This prevents reliable simulation of atmospheric dynamics where infrasound waveguides form. Hence, investigating higher-top atmospheric models enabling simulations at typical operational horizontal resolutions ( km) are of high interest to improve the description of the propagation medium, which is needed to localize and characterizes acoustic sources of interest. The extension of the ICOsahedral Non-hydrostatic (ICON) model to the upper-Atmosphere, UA-ICON with a model-top of 150km, is run at the ICON operational horizontal resolution. Simulations are compared with lidar observations at three different sites and with operational analyses. We demonstrate the better performance of the UA-ICON simulations compared to operational models in the mesosphere, especially for the temperature field while it is less clear for the winds. This is achieved by tuning the non-orographic gravity wave (GW) parameterization coefficient that drives the saturation and breaking of the waves. Additionally, infrasound propagation simulations are performed using UA-ICON atmospheric specifications. For the two case-studies, one at high latitudes and one in tropical regions, we demonstrate the added value of the UA-ICON with a tuned GW parameterization, while also illustrating how infrasound can contribute to model validation and tuning in the upper-atmosphere
Diffusive gradient in thin film for ultra-trace methylmercury measurements in the coastal and open sea
No full textInternational audienceMonomethylmercury (MMHg) is a potent neurotoxin causing neurodevelopmental delays and cardiovascular and immunological issues. Human exposure primarily occurs through seafood consumption due to MMHg bioaccumulation and biomagnification from seawater into marine organisms. Determining MMHg in seawater at ultratrace concentrations poses logistical and analytical challenges. Diffusive Gradient in Thin-film (DGT) samplers represent a promising solution, which captures time-averaged concentrations by preconcentrating in situ MMHg over a defined exposure time. DGT manufactured with 3-mercaptopropyl-functionalized silica (3MFS) in agarose and polyacrylamide gels were tested and compared for the determination of MMHg present in open ocean and coastal waters. Different elution methods using acidic thiourea were tested to reach precise, accurate and quantitative elution of MMHg from the binding gel. We found that polyacrylamide-3MFS binding gels display a higher elution efficiency (94 ± 3 %), precision and better handling compared to agarose-3MFS gels (41 ± 6 %). A unique mooring line installed in the South Western Tropical Pacific Ocean, provided monthly DGT-MMHg concentrations over a year showing potential seasonal differences in MMHg concentrations ranging between 18 and 106 fM. DGT were also deployed in shallow Peruvian coastal waters, exhibiting higher MMHg concentrations (170 ± 97, n = 26) with typical benthopelagic gradients. DGT-MMHg concentrations were in good agreement with discrete water samples analyzed by reference methods using isotope dilution. DGTs offer complementary advantages over oceanographic cruises, notably in situ preconcentration, low blanks, minimal logistical requirements and cost-effectiveness. DGTs represent a valuable tool for studying the marine MMHg cycle for evaluating the implementation of the Minamata Convention
Back to the suture: Bridge River−Hozomeen ribbon cherts reveal long-lived ocean plate stratigraphy and polarity of subduction in western North America
No full textInternational audienceOceanic sutures are important components of accretionary orogens. This study focuses on the Bridge River−Hozomeen terrane, which straddles the Canada-USA border in the Coast-Cascade mountains, and is involved in the debate on the number of oceanic sutures of western North America and their relationships to paleo-Pacific plates (i.e., Andean versus Archipelago models). Currently exposed as two paleo-accretionary complexes offset by Eocene strike-slip faulting, the terrane is dominated by large volumes of mafic rocks and radiolarian chert (ocean plate stratigraphy). Revising the age and distribution of 96 radiolarian localities bearing 350 taxa reveals a long-lived record from the Mississippian to the Middle or Late Jurassic, spanning 170−190 m.y. The radiolarian assemblages are characterized by open-ocean, mixed Tethyan and Panthalassan signatures, likely associated with low-latitude ocean transit scenarios. The distribution of chert ages within the restored accretionary complex suggests a west-younging polarity of the accreted oceanic rocks, which is more consistent with an east-dipping subduction. The Bridge River−Hozomeen suture appears to wrap around the Insular superterrane toward the western oceanic units of Washington state, USA, while another major suture represented by the Cache Creek terrane has more affinities with the Baker terrane in Oregon, USA, and the central Klamath terranes in California, USA. Though exposed on a relatively short segment of the Cordillera, the Bridge River−Hozomeen terrane stands out as a significant paleo-oceanic “window” of western North America
Comparative endocranial anatomy in the crocodylians Leidyosuchus canadensis and Stangerochampsa mccabei from the upper Cretaceous of Alberta, Canada
No full textInternational audienceAbstract Crocodylians evolved a high variety of rostral morphologies during their evolutionary history, highlighting the strong links between morphological plasticity and environmental and ecological parameters. Two Late Cretaceous alligatoroids, the mesorostrine Leidyosuchus canadensi s Lambe, 1907, and the brevirostrine Stangerochampsa mccabei Wu et al., 1996, from Alberta, Canada, preserve a large groove‐shaped recess on the posterior part of the maxilla that has not been documented in other alligatoroids. Despite the potential phylogenetic and paleoecological significance of this neurovascular feature, internal and endocranial structures remain under‐explored among stem alligatoroids. The endocranial morphology, including the paratympanic sinus system of Leidyosuchus canadensis and Stangerochampsa mccabei , was compared to those of extant crocodylians and of the extinct alligatoroid Diplocynodon ratelii based on computed tomography data. The Cretaceous alligatoroids share endocranial features, such as a posteroventral neurovascular projection of the labiolateral canal that connects to the groove‐like recess at the posterior edge of the maxilla and a paratympanic sinus system most similar to those of small‐bodied and young extant crocodylians, suggesting that these pedomorphic features may reflect the ancestral crocodylian condition. Future phylogenetic studies should consider internal and endocranial characters alike to improve our understanding on the relationships among crocodylians
Polarization of the CMB in the Standard Model Extension
No full textInternational audienceIn standard cosmology, Cosmic Microwave Background photons near the last scattering surface exhibit only linear polarization due to Compton scattering, leading to the assumption that primordial circular polarization is negligible. However, the physics of Lorentz violation (LV), associated with specific operators, can influence these polarization characteristics. This study employs the Boltzmann equation within the framework of the Standard Model Extension (SME) to explore how the background LV tensor can induce circular polarization in CMB radiation. By computing the transformation of linear polarization into circular polarization and utilizing the Faraday conversion angle, we derive a bound for on the order of , aligning with recent findings. Additionally, we consider the total pure photon terms within the SME, demonstrating that LV in the presence of scalar perturbations can also generate cosmic birefringence (CB) in the CMB radiation. Through analysis of best-fitting CB angles, we establish a more stringent bound of approximately for
Who’s coming home? Shorter early-life telomeres predict return to the natal colony in an Arctic seabird
No full textInternational audienceIn wild animals, the length of their telomeres, the non-coding DNA sequences protecting the ends of chromosomes, in early life has been shown to predict their performance (eg, survival, reproduction) later in life. However, literature has reported mixed relationships between telomere length (TL) and individual performance, possibly because many previous studies overlooked the effects of the resource-modulated trade-off between growth and telomere maintenance. We investigated the effects of early-life conditions, ie, sibling competition (one or two chicks) and trophic level (nitrogen isotopic values), on the TL of black-legged kittiwake (Rissa tridactyla) chicks while accounting for the growth-TL tradeoff. We also tested whether early-life TL was related to their return probability to the natal colony within six years after fledging (a proxy of survival to adulthood). Although there was no strong evidence for direct effects of the early-life conditions on TL, we found that in broods of two chicks, larger individuals tended to receive a higher-trophic-level diet and have shorter telomeres. This suggests that sibling competition might have imposed stronger resource constraints on the chicks, making them prioritize the limited resources towards growth at the expense of TL. Surprisingly, we found that chicks with shorter telomeres were more likely to return to their colony, whereas body size was not related to return probability, suggesting that TL may be a more comprehensive predictor of return probability than body size. Therefore, our study supports that early-life TL can be a predictor of later-life performance, but it should be used with caution by considering the effect of the resourceallocation trade-off with growth, which can influence the direction of prediction
Disentangling Eastern Pacific Warming: El Niño 2023–2024 vs seasonal Panamá Bay influence
No full textInternational audienceUnderstanding the drivers of coastal ocean warming in the eastern Pacific is critical for distinguishing local variability from large‑scale climate phenomena such as El Niño. This study tests the hypothesis that anomalous warming in northern Ecuadorian coastal waters during January 2024 was primarily driven by the seasonal intrusion of Panamá Bay waters rather than the developing 2023–2024 El Niño event. Oceanographic and meteorological data were collected aboard the Pourquoi Pas? research vessel and compared against climatology (1940–2024), the 1997–1998 El Niño, and satellite observations. Winds were predominantly south-westerly, exceeding climatological averages while sea surface temperatures showed a pronounced south–north gradient. Salinity and mixed‑layer depths remained within seasonal ranges. The Intertropical Convergence Zone persisted north. Comparative analysis revealed weak or absent El Niño signals, with no discernible climatic impacts, wind, rain, thermocline and 20 C depths, T/S relationships, which were within seasonal values corroborated with biological and meteorological indicators. Instead, the seasonal incursion of Panamá Bay waters was the dominant warming driver. These findings refine understanding of eastern Pacific variability and provide the first deep profiles from this region, including serendipitous evidence of Antarctic Intermediate Water at ~1000 m, thereby enhancing observational coverage in a historically undersampled area