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La valorisation agronomique de fertilisants organiques est une source majeure de contamination chronique en cuivre (Cu) et en zinc (Zn) des sols agricoles. La littérature scientifique ne permet pas de trancher sur l'évolution à long-terme de la biodisponibilité pour les organismes du sol de Cu et Zn apportés par les fertilisants organiques. L'objectif de ce travail de thèse a été d'évaluer les déterminants biogéochimiques de la biodisponibilité de Cu et Zn pour les plantes et les vers de terre. Les sols étudiés provenaient d'essais de terrain décennaux conduits à La Réunion, comparant une fertilisation minérale à une fertilisation organique. La biodisponibilité a été déterminée à l'aide de biotests de laboratoire. L'évolution de propriétés chimiques (pH, MOD) ainsi que la disponibilité de Cu et Zn (i.e. concentration totale, activité de l'ion libre et DGT) ont été mesurés dans la solution des sols bio-influencés ou non par la présence des plantes (rhizosphère) et des vers de terre. En l'absence de bio-influence, l'apport de fertilisants organiques a augmenté le pH et la concentration en MOD, diminuant ainsi la disponibilité de Cu et Zn malgré l'augmentation du niveau de contamination du sol. La présence des vers de terre a peu modifié l'effet de l'apport de fertilisants organiques sur les propriétés chimiques et la disponibilité de Cu et Zn. Dans la rhizosphère en revanche, la gamme de variation de pH, de concentration en MOD et donc la disponibilité de Cu et Zn a été réduite par rapport aux sols non bio-influencés et ce entre les modalités de fertilisation. L'effet protecteur induit à la fois par l'apport répété et à long-terme de fertilisants organiques et la bio-influence des organismes, en particulier des plantes dans la rhizosphère, a permis d'expliquer pourquoi la biodisponibilité de Cu et Zn pour les plantes et les vers de terre n'augmentait pas malgré l'augmentation du niveau de contamination du sol.

Les effets de contexte dans la perception de la parole reposent aussi bien sur des sources acoustiques que sémantiques. Le contexte acoustique fournit des informations essentielles pour l’adaptation au locuteur et aux variations dialectales. En parallèle, le contexte sémantique contribue à prédire un ensemble de mots éligibles pour une interprétation licite des énoncés. Afin d’étudier plus précisément les interactions entre ces effets de contexte, nous avons créé une base de données de phrases courtes conçues pour observer ces phénomènes dans des protocoles expérimentaux. Cette base de données est constituée de 28 triplets de phrases porteuses terminées par des cibles de paires minimales de mots CV ou CVC, autour de voyelles acoustiquement proches associées à 4 contrastes vocaliques. Afin d’évaluer la validité des 3 catégories de contexte sémantique considérées, des mesures de similarité sémantique et de fréquence lexicale ont été réalisées à partir de différents corpus de langue française.

L’hypothèse du codage efficace prédit que les systèmes perceptifs sont optimalement adaptés aux propriétés statistiques des signaux naturels. Ce caractère optimal a été récemment évalué sur la base d’analyses statistiques réalisées sur des décompositions spectrales de signaux de parole représentés comme des modulations d’énergie. Ces travaux pourraient trouver des applications directes dans l’amélioration du codage des signaux acoustiques par des implants cochléaires. Cependant, les recherches sur la perception de la musique par des personnes sourdes portant un implant cochléaire mettent en avant des limites qui semblent discordantes avec les performances observées concernant certaines propriétés fondamentales de la parole. Nous comparons les résultats d’analyses statistiques de signaux musicaux avec ceux qui ont été réalisés sur de la parole dans le but d’évaluer les impacts respectifs de ces deux gammes de signaux sonores pour évaluer leurs contributions à cette proposition théorique. Des résultats préliminaires et les perspectives futures sont discutés.

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International audience; Organism activities in soil are able to alter drastically physical-chemical properties, such as pH and dissolved organic matter (DOM) in the bio-influenced area such as rhizosphere for plants and drilosphere for earthworms. These modifications may drive trace element (TE) availability in soil and their bioavailability to soil organisms but with no consistent trends as shown by a literature overview. In this work we studied the effects of plant-earthworm interactions on the copper (Cu) availability in rhizosphere and its consequences on Cu phytoavailability in soils receiving either mineral fertilizers or organic inputs. Plant-earthworm interactions were studied with the RHIZOtest, a biotest that enables to grow plants with their roots in contact with the soil layer (considered as the rhizosphere) but not prenetrating it. The RHIZOtest was deployed here in an original manner: (i) without plant and earthworm (i.e. bulk soil), (ii) with plants (Festuca arrundinaceae) only (i.e. rhizosphere), (iii) with epi-endogeic earthworms (Dichogaster saliens) only (i.e. drilosphere), and (iv) with both plants and earthworms (i.e. rhizo-drilosphere). Two soil samples from the same decadal field experiment were studied, one amended with mineral fertilizers that led to a strongly acidic pH (5.0) and a low organic carbon content (2.0%) and the other amended with cow slurries that led to a ca. neutral pH (6.5) and much higher organic carbon content (2.9%). In order to study the pH as a key parameter, the pH was manipulated and controlled in the rhizosphere, drilosphere, and rhizo-drilosphere either by favoring alkalization or by maintaining the initial bulk-soil pH. Copper availability was determined in bulk soils, rhizospheres, drilospheres and rhizo-drilospheres following (i) a kinetic approach based on the diffusive gradient in thin films (DGT) and (ii) an equilibrium approach based on the measurements of total Cu concentration and Cu2+activity in soil solution. The drivers of Cu speciation in soil solution were assessed by modelling using the windermere humic aqueous model (WHAM). Copper phytoavailability was determined by estimating Cu uptake flux in plants.Results showed that plants and earthworms respectively increased rhizosphere and drilosphere pH when the bulk-soil pH was initially strongly acidic, and decreased rhizosphere and drilosphere DOM concentration. Overall, such physical-chemical changes in the rhizosphere and the drilosphere led to a decrease in Cu availability compared to the initial bulk soil. Results of the biotests are discussed taken into account the hypothesis that plants and earthwormsact synergistically to further reduce Cu availability in the rhizo-drilosphere.

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International audience; Amendments with organic residues (OR) are a major source of copper (Cu) contamination in agricultural soils. The chronic soil contamination with Cu raises the problem of potential toxic effects of Cu on soil organisms and then the long-term sustainability of OR recycling in agriculture. Contrary to heavy soil contaminations, Cu availability in soil and bioavailability to soil organisms remain poorly documented in the context of long-term OR recycling where soil contamination is moderate. The ecotoxicity of Cu depends both on its availability in soil and its bioavailability for soil organisms. In the case of long-term OR applications, Cu availability will be driven by the level of contamination and by temporal evolution of key soil physical-chemical properties such as pH and organic matter content. In the meantime Cu ecotoxicity will depend on the bio-influence of soil organisms on the soil volume they explore i.e. the rhizosphere for plants and the drilosphere for earthworms. The aim of this study was to assess the effect of long-term OR applications on Cu availability in soil and Cu bioavailability to plants and earthworms. A hundred soil samples were selected from four decadal field trials (chronosequences) receiving either no fertilization, mineral fertilization, or organic fertilization and then exhibiting contrasted soil properties. In addition to soil properties we determined Cu availability in each soil sample following (i) a kinetic approach based on the diffusive gradient in thin films (DGT) and (ii) an equilibrium approach based on the measurements of total Cu concentration and Cu2+ activity in soil solution. The drivers of Cu speciation in soil solution were assessed by modelling using the windermere humic aqueous model (WHAM). On the hundred soil samples a sub-selection of thirty soil samples were then exposed to plants (Festuca arrundinaceae) and earthworms (Dichogaster saliens) in biotests. Copper availability in the rhizosphere and drilosphere was measured as detailed above and Cu bioavailability was determined by measuring Cu uptake flux in plants and earthworms. The soil chronosequence analysesrevealed a temporal increase of pH and dissolved organic matter (DOM) that led to an increase in Cu total concentration and a decrease of Cu2+ in soil solution, while DGT-available Cu was not significantly altered. The action of soil organisms, as compared to bulk soil, led to pH further increased while DOM decreased in the rhizosphere and the drilosphere. These evolutions of pH and DOM in the rhizosphere and the drilosphere led to a decrease in total Cu concentration and Cu2+ in soil solution compared to the bulk soil. Copper uptake flux in plants and earthworms revealed that Cu bioavailability to earthworms and plants were not significantly different under long-term organic or mineral or no fertilization. All these results were consistent with the hypothesis that long-term applications of OR, while inducing a chronical soil Cu contamination, still have a protective effect towards Cu ecotoxicity in soil by decreasing Cu availability in soil under physical-chemical and biological control.

Organic wastes (OW) are used as soil amendments and fertilizers but they are alsothe major source of copper (Cu) and zinc (Zn) contamination in agricultural soils.The potential ecotoxicological effects of this contamination on soil organismsdepend on Cu and Zn availability in soils. The availability of Cu and Zn itselfdepends on their chemical speciation and consequently to the temporal evolution ofsoil parameters such as pH and organic carbon content and reactivity. These soilparameters are key parameters both influenced by the application of OW and theactivity of soil organisms on the surrounding soil, i.e. the rhizosphere for plants.However, the concomitant influence of OW applications and rhizosphere effect arepoorly documented when taking into account long-term impacts. Accordingly, weaimed at studying the relationship between the availability in soil and thephytoavailability of Cu and Zn in four decadal field trials that received differenttypes of OW for more than ten years. Soils in the four field trials exhibited verydifferent pH and organic carbon content. Copper and Zn availability wasdetermined on 102 soil samples from the four field trials by (i) an equilibrium-basedmethod using cupric ion selective electrode and the windermere humic aqueousmodel (WHAM) to quantify Cu2+ and Zn2+ activities in soil solutions (pCu2+ andpZn2+) and (ii) a kinetic method using the diffusive gradient in thin films (DGT)directly on soil samples. We measured key soil parameters in soil solutions to assessthe relationship with pCu2+ and pZn2+. Copper and Zn phytoavailability is currentlydetermined using the RHIZOtest which is a standardized biotest that will enable tomeasure the uptake flux of Cu and Zn in plants and the related availability of Cu andZn in the rhizosphere that is physically separated from roots. The results alreadyachieved showed no clear relationship between pCu2+ and pH or dissolved organiccarbon among the four field trials altogether. When studying each trial separately,we observed a pH gradient as a function of the type of fertilizer (mineral or OW)applied, which influence substantially the speciation of Cu in soil. The on-goingmeasurements will enable to test whether Cu and Zn availability in unplanted soilsdetermined Cu and Zn phytoavailability or whether root-induced chemical changesin the rhizosphere additionally determined it.

L’écotoxicologie fait aujourd’hui face à des enjeux qui concernent une meilleure connaissance des effets différés dans le temps et l’espace de mélanges de composés en faibles doses, sur des communautés d’organismes non cibles. Des approches classiquement basées sur l’abondance, a diversité et l’activité des organismes montrent des limites d’interprétation, car souvent soumises à des facteurs confondants ou à des interactions dans un contexte de changements globaux. C’est notamment le cas dans les agroécosystèmes où les pratiques agricoles, la couverture du sol peuvent masquer des effets spécifiques liés à l’apport de contaminants. Nous présentons ici quelques approches en émergence en écotoxicologie terrestre. Elles concernent une meilleure évaluation des dangers, l’amélioration de l’étude des expositions, et, également, la prise en compte d’effets évolutifs et adaptatifs chez les organismes exposés. Des approches intégratives seront également présentées.

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Unrecognized soil algal and cyanobacterial communities as a model, for herbicide risk assessment in agricultural soils. 1ère conférence internationale d’Ecotoxicologie Microbienne, EcotoxicoMic

Exposures of soil microbial communities to realistic antibiotics concentrations: key parameters for environmental risk assessment. 1ère conférence internationale d’Ecotoxicologie Microbienne, EcotoxicoMic

National audience; L'usage des pesticides est une menace pour la biodiversité et l'activité des communautés microbiennes présentes dans les agrosystèmes. L'altération des communautés microbiennes peut avoir des conséquences sur des fonctions écosystémiques conduisant à la diminution de la fertilité et des capacités épuratrices des sols contribuant à diminuer les rendements des cultures et à augmenter la pollution des sols et des eaux, respectivement. Il reste toutefois difficile d'estimer l'impact des pesticides sur des fonctions écosystémiques et de suivre leur résilience suite à des changements de pratique agricole. Dans ce contexte, le projet IMPEC visait à tester et à développer de nouveaux indicateurs microbiens pour estimer l'impact des pesticides sur des fonctions écosystémiques liées au (i) cycle des nutriments et (ii) service épuration des compartiments terrestres et aquatiques. Ces nouveaux indicateurs ont été utilisés pour évaluer a priori et a posteriori l'impact écotoxicologique de pesticides sur la composition taxonomique et sur des traits fonctionnels microbiens des sols et des sédiments. Ils ont été pour partie transférés via le développement de normes ISO pouvant être utilisées pour évaluer l'impact écotoxicologique a priori et a posteriori des pesticides sur les microorgansimes du sol. Une synthèse des principaux résultats du programme IMPEC ainsi que les perspectives en termes de transfert et de recherche seront présentées.

National audience; The consortium AnaEE-France (http://www.anaee-s.fr) aims at understanding and predicting the biodiversity and ecosystems dynamics in a context of global change. It will allow improving the understanding of biotic processes/environment interactions, mobilizing experimental and modelling platforms devoted to the biology of continental ecosystems, both terrestrial and aquatic. In this context, the objectives of the platform Biochem-Env (http://www.biochemenv.fr) are to provide skills and innovative tools for biochemical characterizations of soils, sediments, and micro-macro-organisms living in terrestrial and aquatic ecosystems. These approaches aim to assess ecosystems functioning. The scope of the platform Biochem-Env includes: -the technology intelligence and the development of tools used for the biochemical characterization of solid environmental matrices and macrofauna, -the development of an Environmental Information System (referential for functional biodiversity) for managing the traceability of samples and data, and improve our ability to characterize the biological status of environmental matrices. Available as a scientific partner in the frame of collaborative research projects, the platform’s abilities ranges from advice providing (sampling, protocols and data analysis), to technical training, including analysis and experimentation in regional, national and international research programs. The tools of the platform have been deployed in programs targeted at assessing the sensitivity and restrictions of biological indicators of soil quality, subjected to various constraints (waste landfilling, farming practices, contaminated sites and soils…). For example, long-term experimental sites provide opportunities to assess the effects of pressures and threats on soils and their functioning. In a context of soil contamination, we can conclude using global soil enzymatic activities that soil functioning is enhanced in biological farming comparatively to conventional practices.

Assessment of ecotoxicological impact of pesticides on microbial functions in agroecosystems: how to define suitable indicators and for what purposes?. 7th edition of the International Conference on Pesticide Behaviour in Soils, Water and Air

The significance of soil algae and cyanobacteria in agricultural soils, as a model of soil microbial communities, for the pesticide risk assessment. 7ème Conference on Pesticide Behaviour in Soils, Water and Air

Changement climatique et sols pollués : impact sur les seuils de reponse des organismes du sol. Congrès de la SEFA, 2017

Effets de melanges antibiotiques et elements traces metalliques sur la nitrification dans des sols agricoles: approche experimentale et modélisation. Congrès de la SEFA, 2017

National audience; L’analyse de la parole implique deux dimensions perceptives distinctes : l’identification des propriétés de la voix (caractéristiques vocales, identité du locuteur, genre, état émotionnel…) et la classification en catégories linguistiques (classes phonémiques / traits distinctifs). Ces deux dimensions interagissent largement dans les mécanismes d’identification. Or la perception de parole vocodée peut donner lieu à des baisses de performance dans des contextes multi-locuteurs. Si ces interactions semblent poser relativement peu de problèmes dans la communication quotidienne des auditeurs normo-entendants, indiquant l’existence de mécanismes adaptatifs performants, il est possible que ces phénomènes expliquent les difficultés que peuvent éprouver les patients qui utilisent un implant cochléaire à comprendre la parole dans des situations sonores complexes. Nous avons mis en place une série d’expériences dont l’objectif est d’étudier les mécanismes d’adaptation au changement de longueur du tractus vocal avec de la parole vocodée. Dans le poster, nous décrirons les analyses acoustiques des voyelles du Néerlandais et leur organisation dans un espace formantique en fonction du nombre de canaux de vocodage en nous intéressant aux variations inter-locuteurs et aux manipulations acoustiques qui permettront d’évaluer nos hypothèses, ainsi qu’une expérience d’adaptation au contexte en cours de préparation sur la base de ces analyses.

The stable oxygen isotope composition of atmospheric CO2 and the mixing ratio of carbonyl sulphide (OCS) are potential tracers of biospheric CO2 fluxes at large scales. However, the use of these tracers hinges on our ability to understand and better predict the activity of the enzyme carbonic anhydrase (CA) in different soil microbial groups, including phototrophs. Because different classes of the CA family (α, β and γ) may have different affinities to CO2 and OCS and their expression should also vary between different microbial groups, differences in the community structure could impact the ‘community-integrated’ CA activity differently for CO2 and OCS. Four soils of different pH were incubated in the dark or with a diurnal cycle for forty days to vary the abundance of native phototrophs. Fluxes of CO2, CO18O and OCS were measured to estimate CA activity alongside the abundance of bacteria, fungi and phototrophs. The abundance of soil phototrophs increased most at higher soil pH. In the light, the strength of the soil CO2 sink and the CA-driven CO2-H2O isotopic exchange rates correlated with phototrophs abundance. OCS uptake rates were attributed to fungi whose abundance was positively enhanced in alkaline soils but only in the presence of increased phototrophs. Our findings demonstrate that soil-atmosphere CO2, OCS and CO18O fluxes are strongly regulated by the microbial community structure in response to changes in soil pH and light availability and supports the idea that different members of the microbial community express different classes of CA, with different affinities to CO2 and OCS.

Etudes après études, les pesticides sont identifiés comme une menace pour la diversité et l’activité des microorganismes des sols. Bien que cette menace soit identifiée, nous restons démunis pour estimer l’impact écotoxicologique des pesticides sur des fonctions écosystémiques des sols. Ainsi, l’évaluation a priori des effets des pesticides sur les microorganismes des sols repose sur l’estimation de leur impact sur la minéralisation du carbone et de l’azote. Ces tests trop globaux ne rendent pas compte de l’effet des pesticides sur les microorganismes. Cette étude a testé un bouquet d’indicateurs pour évaluer l’impact écotoxicologique de pesticides sur les communautés microbiennes supportant des fonctions écosystémiques des sols et des sédiments. Elle a permis le développement de nouveaux outils et de normes ISO pouvant être utilisés pour évaluer l’impact a priori et a posteriori des pesticides sur la diversité et l’activité des microorganismes des sols et des sédiments., What microbial indicators to assess the ecotoxicological impact of pesticides on terrestrial and aquatic ecosystem functions? Studies after studies, pesticides are identified as a major threat for the diversity and activity of soil microorganisms. Although identified as a threat, there is a lack of methods to estimate the ecotoxicological impact of pesticides on soil ecosystemic functions. Indeed a priori evaluation of pesticide effects on soil microorganisms relies solely on the estimation of their impact on carbon and nitrogen mineralisation. These global tests did not allow to properly measure the effects of pesticides on soil microorganisms. This study tested a panel of indicators to evaluate the ecotoxicological impact of pesticides on microbial communities supporting soil and sediment ecosystemic functions. It leads to the development of new tools and ISO standards ready to be used to evaluate the a priori and a posteriori impact of pesticides on the diversity and activity of soil and sediment microorganisms.

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Ce numéro comprend les articles issus du colloque de restitution Ecophyto Recherche « Des outils et des dispositifs pour éclairer les décisions, explorer les possibles et accompagner la transition vers des systèmes économes et multi-performants », qui s’est tenu à Saint-Malo, du 22 au 24 mars 2017.; Quels indicateurs microbiens pour évaluer l’impact écotoxicologique des pesticides sur des fonctions écosystémiques terrestres et aquatiques ?

National audience

The stable oxygen isotope composition of atmospheric CO2 and the mixing ratio of carbonyl sulphide (OCS) are potential tracers of biospheric CO2 fluxes at large scales. However, the use of these tracers hinges on our ability to understand and better predict the activity of the enzyme carbonic anhydrase (CA) in different soil microbial groups, including phototrophs. Because different classes of the CA family (α, β and γ) may have different affinities to CO2 and OCS and their expression should also vary between different microbial groups, differences in the community structure could impact the ‘community-integrated’ CA activity differently for CO2 and OCS. Four soils of different pH were incubated in the dark or with a diurnal cycle for forty days to vary the abundance of native phototrophs. Fluxes of CO2, CO18O and OCS were measured to estimate CA activity alongside the abundance of bacteria, fungi and phototrophs. The abundance of soil phototrophs increased most at higher soil pH. In the light, the strength of the soil CO2 sink and the CA-driven CO2-H2O isotopic exchange rates correlated with phototrophs abundance. OCS uptake rates were attributed to fungi whose abundance was positively enhanced in alkaline soils but only in the presence of increased phototrophs. Our findings demonstrate that soil-atmosphere CO2, OCS and CO18O fluxes are strongly regulated by the microbial community structure in response to changes in soil pH and light availability and supports the idea that different members of the microbial community express different classes of CA, with different affinities to CO2 and OCS.

Les microalgues et cyanobactéries édaphiques : écologie et rôles en bioindication

A new UHPLC-MS/MS analytical method to assess the environmental availability of sulfamethoxazole and three transformation products in soil amended with manure. 1st International Conference on the Risk Assessment of PHarmaceuticals in the Environment

Ecotoxicological impact of an antibiotic mixture on soil nitrogen cycling microbial guilds. First International Conference on Risk Assessment of Pharmaceuticals in the Environment (ICRAPHE)

Background and objectivesThe fate and effects of human and veterinary antibiotics in the environment have been the subject of intense investigation for nearly two decades. While the occurrence and persistence of antibiotics and antimicrobial resistance in environment have become major human health and research issues, their impacts on microbial ecosystem processes (i.e. nutrient recycling) are not well-understood. Many gaps still persist regarding the ecotoxicological assessment of antibiotics as related to environmental risk assessment (ERA). ERA researches have been mainly focused on normalized single species bioassay, and current ecotoxicological studies should aim at bridging the gap existing in the understanding and assessment of antibiotic impact on microbial ecosystem processes. The ERA methodologies for antibiotics have been developed based on the current standard ecotoxicology tests existing guidelines for other chemicals, but such regulatory assessment has been questioned (Boxall et al., 2012). Actually, the modes of action of antibiotics are mainly specific for bacteria, but for bacterial toxicity tests play only a minor role during the ecotoxicological assessment of antibiotics (Kümmerer et al., 2004; Brandt et al., 2015). Consequently, this may overlook adverse effects of antibiotics on microbial ecosystem functions. This issue additionally requires the characterization of the community – function relationships, to identify sensitive, resistant and resilient populations, and the main edaphic factors controlling antibiotic availability and thus microbial exposure to antibiotic. The growing interest for organic wastes recycling as soil amendments, can lead to various diffuse antibiotic contaminations, requiring an ecotoxicological assessment of such agricultural practice. The scope of this work aims at identifying microbial community-based tests and endpoints to improve targeted protection of key microbial soil processes and also unravel the diversity – function relationships involving in the resilience of soil microbial functioning, following application of contaminated amendments. Methods and resultsHere, we investigated the effects of sulfamethoxazole (SMX) on microbial nitrogen transformations. A dose-effect approach was performed with different doses of SMX added to different organic wastes (compost of sewage sludge - green waste (SGW), farmyard manure (FYM)), before their mixing with soil, in microcosms. The final concentrations of SMX in amended soils ranged from 0.022 to 2.22 mg kg-1dw, with control soil microcosms amended with SGW or FYM without SMX. Nitrogen forms, potential nitrification and denitrification activities were determined in soils, after 8, 28 and 84 days following amendments. Abundances and composition of specific microbial guilds (ammonia oxidizing bacteria and archae and some denitrifiers) were determined with molecular tools. The total and available concentrations of SMX were extracted with organic and aqueous solutions, respectively, and then quantified by UHPLC-MS/MS.Discussion and conclusionsOnly the nitrification activity was adversely impaired by SMX, following a dose-response pattern, in SGW amended soils, but not in FYM amended soils. These effects had short-term outcomes for nitrogen nutrient dynamic, decreasing soil nitrate content, SGW amended soils, from 0.22 mg SMX kg-1dw. Organic matter is a key environmental factor influencing the bioavailability and the effects of antibiotics on soil microorganisms. In this experiment, the chemical assessment of SMX availability did not show strong differences between the SGW or FYM amended soils. Actually, the acute toxicity of SMX, following a bacteriostatic action, can be only detected on growing microbial populations, such as nitrifiers, in SGW amended soils with high NH4+ levels. Denitrification activity was only slightly affected by high SMX doses, in SGW amended soils, despite an obvious non limitation of nutrients (nitrate and organic carbon) improving population growth. Different level of taxonomic diversity can explain this different sensitivity between nitrification and denitrification. In addition, the magnitude of effects of low doses of SMX (from 0.22 to 0.66 mg kg-1dw) slightly decreased after 84 days of exposure, compared to days 8 and 28, in accordance with the decrease of SMX availability, measured in SGW amended soils. Analytical chemistry (See presentation Goulas et al.) improves our understanding of community responses, with the determination of the exposure to antibiotics. Furthermore, modification of community composition could contribute to the functional resilience against antibiotic stress, through the substitution of sensitive taxa by more tolerant taxa which can colonize vacant niche (Ollivier et al., 2013).This work reveals that, in high nutrient context, soil nitrification appeared as a sensitive indicator of SMX effects on soil microbial functioning, while denitrification was more resistant. Also, close to realistic environmental concentration, the results highlighted resilience of soil nitrification, following a short-term impairment. The dissipation of SMX, leading to a decrease of soil microorganism exposure, promoted this resilience, in addition to changes in community composition. The availability of antibiotic and ecological characteristics of microbial communities (resistance and resilience) must be integrated in ERA methodologies.Boxall A, Rudd M.A, Brooks B.W., …Topp E, Van Der Kraak G. 2012. Pharmaceuticals and personal care products in the environment: what are the big questions? Environ Health Perspect. 120, 1221–1229.Brandt KK, Topp E, et al., 2015. Ecotoxicological assessment of antibiotics: A call for improved consideration of microorganisms. Environ Inter. 85, 189–205.Kümmerer K, Alexy R, Hüttig J, Schöll A. 2004. Standardized tests fail to assess the effects of antibiotics on environmental bacteria. Water Res. 38, 2111–2116.Ollivier J, Schacht D, Kindler R, Groeneweg J, Engel M, Wilke B-M, Kleineidam K and Schloter M. 2013. Effects of repeated application of sulfadiazine-contaminated pig manure on the abundance and diversity of ammonia and nitrite oxidizers in the root-rhizosphere complex of pasture plants under field conditions. Front Microbio. 4, 22.

Background and objective :During the last two decades, the environmental concern regarding the antibiotics has increased considerably. The persistence of both antibiotics and antimicrobial resistances in the environment has become a major human health and research issue. However their ecotoxicological impacts on microbial ecosystem functions involving in biogeochemical processes, are still not well-understood (Roose-Amsaleg & Laverman, 2016). Furthermore, the environmental risk assessment, based on existing guidelines for other chemicals, may overlook adverse effects of antibiotics on environmental microorganisms and related functions (Boxall et al., 2012), due to the lack of representativeness of ecotoxicological tests for bacterial toxicity in guidelines for environmental risk assessment of antibiotics. In addition, while ecosystems are contaminated by mixtures of chemicals rather than individual substances, toxicity mixture effects of antibiotics on key microbial processes have been not investigated (Brandt et al., 2015). The scope of this study was to unravel the mixture toxicity of antibiotics on soil microbial nitrification and denitrification processes, to improve knowledge of suitable ecotoxicological endpoints, for risk assessment.Methods and results : The tested antibiotics were belonged to several classes (tetracycline, sulfonamide, macrolide, fluoroquinolone) with various modes of action. The effects of each antibiotic individually and as mixtures were assessed across dose-response approaches (performed with R software, DRC package) on potential nitrification in slurry bioassay (NF EN ISO 14238) and denitrification (Roose-Amsaleg et al., 2013) of soil microbial communities. Antibiotic mixtures were built-up in order to test additivity, based on Toxic Unit (TU) ratio, in addition to other mixtures close to environmental surveys (literature data). The antibiotic exposure was verified by measuring the concentrations of antibiotics at the beginning and the end of the experience. Complementary investigations were realized on community structure parameters of specific N-cycling microbial guilds with molecular approaches, to help us in identifying key actors involving in structure – function relationships (species interaction). The first results demonstrated strong differences of magnitude effect among each antibiotic individually, in relation with the mode of action of AB and different levels of sorption on soil components, influencing their bioavailability in the nitrification bioassay. The results of the experimental approaches were analyzed regarding mathematical modeling interpretation based on the concepts of concentration addition or independent action. In many cases, independent action concept better predicted mixture toxicity of different classes of antibiotics, harboring different mode of action. The responses of structural parameters of microbial guilds were observed at higher concentration than the functional endpoints. The decreases of abundances of several microbial groups were correlated with those of the respective activities.Discussion and conclusion : Ecotoxicological effects were recorded at very low concentrations, in our bioassays, based on model microbial communities, in optimal growth conditions. These conditions are not representative of the bulk soil conditions but can correspond to some microbial hot-spots in functional domains, in soils (i.e. rhizosphere). Whilst many previous studies have mainly focused on normalized single species bioassay, significant well-designed studies, improving the integration of ecotoxicological endpoints at the community level, should grab the existing gap on understanding and environmental assessment of mixture impact on microbial ecosystem processes. The archeal nitryfiers / bacterial nitrifyers ratio seems to be related to the magnitude of nitrification responses, only for some antibiotic and the mixture (Konopka et al., 2015). These results can be explained by the lower sensitivity of Archeae to certain antibiotics, notably those targeting the bacterial cell-wall components.

International audience; As a service of the research infrastructure AnaEE-France (http://www.anaee-france.fr/fr/), the platform Biochem-Env (http://www.biochemenv.fr) offers skills and innovative analytical tools for biochemical characterizations of soils, sediments, and micro-macro-organisms living in terrestrial and aquatic ecosystems. The platform provides methods validated according to Quality Guidelines, i.e. to measure global soil enzymatic activities. Our robot-supported protocols allow great number of enzyme measurements (hydrolase and oxidase activities) with high reproducibility. It has been involved in programs targeted at assessing the sensitivity and restrictions of biological indicators of soil quality, subjected to various constraints (waste landfilling, farming practices, contaminated sites and soils…). The platform is also at the origin of an ISO standard (ISO_TS_22939). Available as a scientific partner in the frame of collaborative research projects, the platform’s abilities ranges from advice providing (sampling, protocols and data analysis), to technical training, including analysis and experimentation in regional, national and international research programs.

International audience; Static and dynamic characterization of vowels in VV sequences. The present study aims at evaluating the respective contributions of static and dynamic cues to vowel classification. Formant cues from six french vowels and sixteen V1V2 slope transitions were extracted in order to investigate the respective contributions of dynamic and static cues that would be respectively related to transitions or center frequencies. The corresponding data were collected from a dedicated task in which speech rate was influenced experimentally in order to trigger potential variations of rate of change within the transitions. The current results do not favour any of the two potential accounts but show that dynamic cues may be as reliable as static ones. Follow-ups to this protocol are offered that may contribute to this issue more informatively.; Nous étudions les indices acoustiques liés à la caractérisation statique et / ou dynamique des voyelles du français. Nous avons analysé les caractéristiques formantiques de six réalisations vocaliques ainsi que les transitions formantiques de seize combinaisons V1V2 impliquant ces 6 voyelles afin d'évaluer les contributions des indices dynamiques liés aux transitions entre voyelles et des indices statiques de fréquence. Les mesures correspondantes sont issues d'un protocole dans lequel le débit de parole était influencé expérimentalement afin de provoquer d'éventuelles variations de vitesse de transition. Les résultats ne permettent pas de départager ces deux hypothèses mais montrent que les indices dynamiques pourraient être aussi fiables que les mesures statiques. Des pistes d'extension de ce travail sont proposées qui pourraient contribuer de manière plus informative à cette problématique.