Impact des changements globaux sur le fonctionnement des tourbières‎ : couplage C-N-S et interactions biotiques

In a context of global change, peatlands "sink" function of carbon (C) is likely to switch to a "source" function, releasing into the atmosphere large quantities of C initially stored in the peat. This thesis aims to characterize and quantify at different levels of organization: i) the impact of global warming on Sphagnum-peatland biogeochemical functioning (CNS) and ii) the impact of restoration of peatland abandoned after harvesting of peat on the interactions between recolonizing plants (Eriophorum angustifolium), macrofauna (Lumbricus rubellus) and the microorganisms potentially involved in the regeneration process of peat forming. The peatland functioning and biotic interactions have been studied by coupling C-N-S and isotope tracing 13C-15N-34S. A moderate increase of + 1°C simulated by "Open Top Chambers" (OTCs) significantly reduces C fluxes at the ecosystem level, the primary production of Sphagnum and the microbes are most affected. At the community level, the activity of anaerobic bacteria, fungi and protozoa (estimated by SIP 13C-PLFAs) was significantly slowed. We showed that a soil engineer as the earthworm L. rubellus played a positive role in recycling organic matter indirectly by providing elements (C > N > S) to the plant. Transfers depend on the functional traits of the organism. At the individual level, we have characterized using NanoSIMS, "anticorrelated" NS transfers from earthworms to peat.Dans un contexte de changements globaux, la fonction de "puits" de carbone (C) des tourbières est susceptible de basculer vers une fonction "source", en libérant dans l'atmosphère de grandes quantités de C initialement stockées dans la tourbe. Cette thèse vise à caractériser et quantifier, à différents niveaux d'organisation, i) l'impact d'un réchauffement climatique sur le fonctionnement biogéochimique (C-N-S) d'une tourbière à Sphaignes et ii) l'impact de la restauration d'une tourbière abandonnée après exploitation sur les interactions entre les plantes recolonisatrices (Eriophorum angustifolium), la macrofaune (Lumbricus rubellus) et les microorganismes potentiellement impliqués dans la régénération du processus de tourbification. Le fonctionnement de la tourbière et les interactions biotiques ont été étudiées par couplage des cycles C-N-S et traçage isotopique 13C-15N-34S. Une augmentation modérée de + 1°C simulée par "Open Top Chambers" (OTCs) diminue significativement les flux de C à l'échelle de l'écosystème, la production primaire des Sphaignes et le compartiment microbien étant les plus affectés. A l'échelle des communautés, l'activité des bactéries anaérobies, des champignons et des protozoaires (estimée par SIP 13C-PLFAs) est significativement ralentie. Nous avons montré qu'un organisme ingénieur comme le ver de terre L. rubellus jouait un rôle positif dans le recyclage de la matière organique en fournissant indirectement des éléments (C > N > S) à la plante. Ces transferts seraient dépendants des traits fonctionnels de l'organisme. A l'échelle de l'individu, nous avons caractérisé par approche NanoSIMS, les transferts "anticorrélés" N-S ver de terre --> tourbe

Impact des changements globaux sur le fonctionnement des tourbières‎ : couplage C-N-S et interactions biotiques

In a context of global change, peatlands "sink" function of carbon (C) is likely to switch to a "source" function, releasing into the atmosphere large quantities of C initially stored in the peat. This thesis aims to characterize and quantify at different levels of organization: i) the impact of global warming on Sphagnum-peatland biogeochemical functioning (CNS) and ii) the impact of restoration of peatland abandoned after harvesting of peat on the interactions between recolonizing plants (Eriophorum angustifolium), macrofauna (Lumbricus rubellus) and the microorganisms potentially involved in the regeneration process of peat forming. The peatland functioning and biotic interactions have been studied by coupling C-N-S and isotope tracing 13C-15N-34S. A moderate increase of + 1°C simulated by "Open Top Chambers" (OTCs) significantly reduces C fluxes at the ecosystem level, the primary production of Sphagnum and the microbes are most affected. At the community level, the activity of anaerobic bacteria, fungi and protozoa (estimated by SIP 13C-PLFAs) was significantly slowed. We showed that a soil engineer as the earthworm L. rubellus played a positive role in recycling organic matter indirectly by providing elements (C > N > S) to the plant. Transfers depend on the functional traits of the organism. At the individual level, we have characterized using NanoSIMS, "anticorrelated" NS transfers from earthworms to peat.Dans un contexte de changements globaux, la fonction de "puits" de carbone (C) des tourbières est susceptible de basculer vers une fonction "source", en libérant dans l'atmosphère de grandes quantités de C initialement stockées dans la tourbe. Cette thèse vise à caractériser et quantifier, à différents niveaux d'organisation, i) l'impact d'un réchauffement climatique sur le fonctionnement biogéochimique (C-N-S) d'une tourbière à Sphaignes et ii) l'impact de la restauration d'une tourbière abandonnée après exploitation sur les interactions entre les plantes recolonisatrices (Eriophorum angustifolium), la macrofaune (Lumbricus rubellus) et les microorganismes potentiellement impliqués dans la régénération du processus de tourbification. Le fonctionnement de la tourbière et les interactions biotiques ont été étudiées par couplage des cycles C-N-S et traçage isotopique 13C-15N-34S. Une augmentation modérée de + 1°C simulée par "Open Top Chambers" (OTCs) diminue significativement les flux de C à l'échelle de l'écosystème, la production primaire des Sphaignes et le compartiment microbien étant les plus affectés. A l'échelle des communautés, l'activité des bactéries anaérobies, des champignons et des protozoaires (estimée par SIP 13C-PLFAs) est significativement ralentie. Nous avons montré qu'un organisme ingénieur comme le ver de terre L. rubellus jouait un rôle positif dans le recyclage de la matière organique en fournissant indirectement des éléments (C > N > S) à la plante. Ces transferts seraient dépendants des traits fonctionnels de l'organisme. A l'échelle de l'individu, nous avons caractérisé par approche NanoSIMS, les transferts "anticorrélés" N-S ver de terre --> tourbe

Impact des changements globaux sur le fonctionnement des tourbières (couplage C-N-S et interactions biotiques)

Dans un contexte de changements globaux, la fonction de "puits" de carbone (C) des tourbières est susceptible de basculer vers une fonction "source", en libérant dans l'atmosphère de grandes quantités de C initialement stockées dans la tourbe. Cette thèse vise à caractériser et quantifier, à différents niveaux d'organisation, i) l'impact d'un réchauffement climatique sur le fonctionnement biogéochimique (C-N-S) d'une tourbière à Sphaignes et ii) l'impact de la restauration d'une tourbière abandonnée après exploitation sur les interactions entre les plantes recolonisatrices (Eriophorum angustifolium), la macrofaune (Lumbricus rubellus) et les microorganismes potentiellement impliqués dans la régénération du processus de tourbification. Le fonctionnement de la tourbière et les interactions biotiques ont été étudiées par couplage des cycles C-N-S et traçage isotopique 13C-15N-34S. Une augmentation modérée de + 1C simulée par "Open Top Chambers" (OTCs) diminue significativement les flux de C à l'échelle de l'écosystème, la production primaire des Sphaignes et le compartiment microbien étant les plus affectés. A l'échelle des communautés, l'activité des bactéries anaérobies, des champignons et des protozoaires (estimée par SIP 13C-PLFAs) est significativement ralentie. Nous avons montré qu'un organisme ingénieur comme le ver de terre L. rubellus jouait un rôle positif dans le recyclage de la matière organique en fournissant indirectement des éléments (C > N > S) à la plante. Ces transferts seraient dépendants des traits fonctionnels de l'organisme. A l'échelle de l'individu, nous avons caractérisé par approche NanoSIMS, les transferts "anticorrélés" N-S ver de terre -> tourbe.In a context of global change, peatlands "sink" function of carbon (C) is likely to switch to a "source" function, releasing into the atmosphere large quantities of C initially stored in the peat. This thesis aims to characterize and quantify at different levels of organization: i) the impact of global warming on Sphagnum-peatland biogeochemical functioning (CNS) and ii) the impact of restoration of peatland abandoned after harvesting of peat on the interactions between recolonizing plants (Eriophorum angustifolium), macrofauna (Lumbricus rubellus) and the microorganisms potentially involved in the regeneration process of peat forming. The peatland functioning and biotic interactions have been studied by coupling C-N-S and isotope tracing 13C-15N-34S. A moderate increase of + 1C simulated by "Open Top Chambers" (OTCs) significantly reduces C fluxes at the ecosystem level, the primary production of Sphagnum and the microbes are most affected. At the community level, the activity of anaerobic bacteria, fungi and protozoa (estimated by SIP 13C-PLFAs) was significantly slowed. We showed that a soil engineer as the earthworm L. rubellus played a positive role in recycling organic matter indirectly by providing elements (C > N > S) to the plant. Transfers depend on the functional traits of the organism. At the individual level, we have characterized using NanoSIMS, "anticorrelated" NS transfers from earthworms to peat.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Visualization and quantification of C-N-S transfers by soil engineers using manoSIMs.

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Suitability of high-resolution mass spectrometry in analytical toxicology: Focus on drugs of abuse

International audienceHigh-resolution mass spectrometry (HRMS) is now the method of choice in several toxicology contexts. This paper reviews HRMS approaches for research and application in various toxicology fields, focusing on drugs of abuse in clinical and forensic toxicology. Papers concerning HRMS applications in screening, quantification and metabolism of drugs of abuse in biological and non-biological samples were included. Specific applications for new psychoactive substances in contexts such as online libraries, bioinformatic tools (molecular networking) and methods combinations were also included. (C) 2021 Societe Francaise de Toxicologie Analytique. Published by Elsevier Masson SAS. All rights reserved

Mise en évidence d’intoxications par ingestion de champignons supérieurs : expérience au CHU de Rennes

National audienceL'α- et la β-amanitine sont de puissantes toxines de champignons supérieurs responsables de cytolyses hépatiques graves pouvant menacer le pronostic vital. En France, les données des centres antipoison rapportent un nombre croissant d'intoxications aux champignons depuis 2016, justifiant le besoin de méthodes de diagnostic biologique robustes. En laboratoire de toxicologie hospitalière, l'objectivation d'une intoxication par les amanitines à partir de prélèvements sanguins ou urinaires constitue ainsi un élément important dans la prise en charge du patient intoxiqué. L'objectif de ce travail consiste à réaliser une mini-revue de la littérature sur le dosage des amanitines dans les fluides biologiques pour le diagnostic des intoxications aux amanitines. Les caractéristiques des amanitines, les méthodes analytiques, les données d'interprétation, les applications pratiques ainsi que les perspectives d'utilisation des techniques de dosage y sont présentées. À travers une comparaison de deux techniques analytiques de chromatographie liquide couplée à de la spectrométrie de masse en tandem utilisées au Centre hospitalier universitaire de Rennes (Waters Xevo TQ XSTM et Thermo Scientific Q ExactiveTM), cet article présente également le retour d'expérience de biologistes médicaux dans l'amélioration continue des méthodes de dosages des amanitines

Magic truffle intoxication: A case report

International audienceUnusual forms of hallucinogenic mushrooms are emerging, which may delay diagnosis and compromise optimal management. Here, we discuss clinical and biological findings in a case of "magic mushroom" intoxication in a 20-year-old man who was brought to hospital emergency department in a state of euphoria, disorientation, intense visual hallucinations, episodic amnesia and agitation requiring physical restraint. The patient's family brought intact specimens of the consumed product, without any health professional being able to identify it. Toxicological screening detected psilocin in urine and in the unknown mushrooms, allowing guiding the mushroom identification towards the Psilocybes genus. Ten hours post-ingestion, the patient was discharged asymptomatic. We believe that recognition of the unusual form of hallucinogenic mushroom presented here by emergency physicians might contribute to better diagnosis and subsequent optimal management, especially since hallucinogenic substances are not routinely tested in toxicological analyses

Effects of soil engineers in C-N-S coupling in a regenerating cutover peatland.

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Understanding the fate and linkage of N and S in earthworm engineered peat soil using nanoSIMS

International audienceEarthworms, by changing soil physical properties, are efficient engineers that play a key role on the soil nutrient dynamics but their biological processes at the micrometric scale are still misunderstood. The nano-scale secondary ion mass spectrometry (NanoSIMS) is a new tool in the study of biophysical interfaces in soils with its ability to operate at high mass resolution, while maintaining both excellent signal transmission and high spatial resolution (down 50 nm). Based on this new technology, the aim of this study was to visualize at the micrometric scale the burrow-linings of Lumbricus rubellus L. and to determine the fate and linkage of nitrogen (N) and sulphur (S) deriving from this soil engineer. Earthworms were triple labelled with isotopic tracers (15N and 34S) prior to introduction into unlabelled peat mesocosms for 24 days. Then, mesocosms were embedded in a polyester resin to carry out the NanoSIMS analysis (NanoSIMS 50™; Cameca, Gennevilliers, France). Burrow-linings were analysed with a transect of images increasingly far of the biophysical interface (from poral space to inner of the burrow-lining) and we assessed the linkage of 15N and 34S with the soil micro-architecture by using the linescan technique. Isotopic compositions were determined by using image processing with the ImageJ software (W.S. Rasband, US National Institutes of Health) and thus nutrients transfers from labelled earthworms to soil burrow-linings were detected. We had a visible gradient with a decrease of percentage of 15N and 34S (2.00 to 0.38 % and 10.0 to 4.4 % respectively) and no transfer was detected beyond 1mm, which defined clearly the area of earthworm's influence (i.e. the drilosphere). Interestingly, the occurrence of spatially anti-correlated hotspots of 15N and 34S suggested either i) two kinds of earthworm's excretions (an excretion rich in N and poor in S, and an excretion poor in N and rich in S) or ii) two kinds of microbial activity linked with N or S cycle (15N or 34S microbial uptake). The speciation of these enriched hotspots are currently under analyzes. By using the NanoSIMS tool coupled with isotopic tracers, we bring out new understandings of the impact of earthworms on the nutrients and thus their ability to sustain hot spots of microbial activity in cutover peat

Understanding the fate and linkage of N and S in earthworm-engineered peat soil by coupling stable isotopes and nano-scale secondary ion mass spectrometry

Document Type : Proceedings Paper Conference Date : SEP 19-23, 2010 Conference Location : FRANCE Conference Sponsor : Bioemco Lab (Biogeochemistry and Ecol Continental Ecosystems), Soil Organ Matter GrpInternational audienceEarthworm burrow-lining is a biophysical interface where the relationship between the spatial location of active soil microorganisms and the actual physical structure of the soil has a major influence on geochemical processes and nutrient cycling. Isotopic tracers and NanoSIMS were combined to highlight, at the nanometric scale, N and S transfers from earthworms to this non-destructured biophysical interface. Peat mesocosms were inoculated with double labelled earthworms (15N and 34S; Lumbricus rubellus H.) and then sampled for NanoSIMS quantitative measurements. The maximum enrichments of 15N and 34S detected in peat after 24 days were 1.6 and 5.6 APE (Atom % excess), respectively. NanoSIMS analyses, performed along a transect in peat at increasing distances from contact between the epidermis of an earthworm and its burrow-lining, revealed rapid and brief transfers of biogenic N and S into peat with two contrasted distributions i.e., decreasing 15N and patchy 34S. The sphere of influence of L. rubellus was clearly delimited after 24 days at 1 mm around the burrow, thus specifying the functional traits of this epi-anecic earthworm. The observed N inputs into peat were probably derived from oxidation of the labile products of earthworm metabolism, such as urea and/or ammonium, as shown by the strong linkage of 15N with oxygen measured as 16O−. The transfers of labile S products from earthworm to the surrounding soil are reported here for the first time and could be derived from mucoprotein secretion. The interesting spatially inverse relationship between 15N and 34S enriched-spots at increasing distances from the burrow-lining highlighted different fates of the biogenic N and S compounds excreted by earthworms and could reveal the activities of syntrophic partnerships in N and S cycling. The strategy of combining isotopic tracers with NanoSIMS demonstrated high potential for determining the fate of biogenic nutrient inputs occurring in a complex matrix such as soil. It opens up considerable opportunities to link the biological traits of specific soil engineers with geochemical processes operating at the microbial scale in the spatial structure created by earthworms