-Biomonitoring is central to the European Union's Water Framework Directive (WFD) and to the French water and aquatic environmental law, but most diatom indices do not separate different anthropogenic impacts. To address this gap, the effect of water chemistry on diatom ecological guilds and life forms was assessed in order to indicate stream perturbations. Generalised additive models (GAMs) were built on a large-scale data set of 1571 samples from the French monitoring network. The relationships between diatom ecological guild and life form metrics were investigated by Principal components analysis and the results predicted by GAMs. The models characterised eight chemical parameters that modified adaptive strategies (ecological guilds) and growth morphology (life forms). Total phosphorus, conductivity, nitrate and pH are the main influencing factors, followed by temperature, dissolved oxygen and organic matter. The findings confirm three groups of diatoms with different adaptive strategies: 1 -fast moving species, 2 -species growing close to the substrate and 3 -species extending to the surface layers of the biofilm. Thirteen diatom metrics displayed a variety of responses to different ranges of the eight chemical parameters. These metrics could be used to help to identify and quantify which chemical alterations are caused by polluted effluents in rivers.Keywords: benthic diatoms / ecological guilds / biological traits / biomonitoring / generalised additive model Résumé -Modélisation des formes de vie et guildes écologiques des diatomées pour la bioindication en rivières. La bioindication est centrale dans la directive cadre européenne sur l'eau et la loi française sur l'eau, mais la plupart des indices diatomiques ne séparent pas les différents impacts anthropiques. Pour combler ce manque, l'effet de la physico-chimie de l'eau sur les guildes écologiques et formes de vies des diatomées a été étudié pour indiquer des perturbations des cours d'eau. Des modèles additifs généralisés (GAMs) ont été construits sur un jeu de données de 1571 échantillons des réseaux de suivi des cours d'eau français. Les relations entre les métriques de guildes écologiques et formes de vie des diatomées ont été étudiées par une ACP et les résultats prédits par des GAMs. Les modèles ont caractérisé huit paramètres physico-chimiques qui modifient les stratégies adaptatives (guildes écologiques) et morphologies de croissance (formes de vie). Le phosphore total, la conductivité, les nitrates et le pH sont les facteurs les plus influents, suivis par la température, l'oxygène dissous et la matière organique. Les résultats confirment trois groupes de diatomées avec des stratégies adaptatives différentes : 1 -les espèces se déplaçant rapidement, 2 -les espèces proches du substrat et 3 -les espèces s'étendant vers la surface du biofilm. Quatorze métriques diatomiques ont montré une variété de réponses à différentes gammes de valeurs des huit paramètres physico-chimiques. Ces métriques pourraient être utilisées pour aider à identifier ...

International audienceIn Europe, the number of establishment of non-native species, especially from Ponto-Caspian area, has dramatically increased over the past decades and induced important changes in macroinvertebrate assemblages, mainly in large rivers. However, although many Ponto-Caspian species were established in adjacent countries, only two Ponto-Caspian amphipods were formally observed in French hydrosystems since 1996. To update our knowledge on the present distribution of the Ponto-Caspian species in France, we collected amphipods from 203 sites in the Rhine, Meuse and Seine River basins in 2008 and again in 2009. Thirteen amphipod species were found in the study area. Among them, four were first formally recorded in France (Dikerogammarus haemobaphes, Dikerogammarus bispinosus, Echinogammarus ischnus, and Echinogammarus trichiatus). Our study revealed three different corridors used by these species to arrive in France. We also observed a different pattern of colonization for each species, which might indicate some between-species differences in their preferences for environmental conditions. The snapshot of the early distributions of these recently established species may hence be used to study the invasion pattern in France in order to manage their potential impact in and outside France

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International audienceChemical and biological assessments of waterbodies are required to fulfil the objectives of the European Water Framework Directive (EU Off J 327:1–72, 2000). Many past studies have been focused on water chemistry uncertainties, but few have been carried out on the hydrobiological aspects. Considerable research on macroinvertebrates has highlighted the mosaic habitat impact on the macroinvertebrate distribution, substrate type and within-substrate heterogeneity as uncertainty sources. We thus studied the effect of substrate variability on the metrics of two French biological indices (normalized index IBGN and new index I2M2 metrics) using experimental field sampling based on substrate replicates. For each of the nine substrates studied, a minimum of 2 sites were selected (among a total of 31 sites) in 7 hydroecoregions (HER). Ten replicates per substrate and site were collected where possible. We obtained 315 faunistic lists associated with 315 substrate replicates. Twelve metrics, such as the Shannon index and variety class, were calculated by list. We used multidimensional scaling and similarity indices to analyse the substrate variability effect. Our results highlighted the extent of HER and site features on the within-substrate heterogeneity. Faunistic lists and metrics varied more in root and sand substrates than in other substrates. I2M2 metrics, i.e. ASPT, taxonomic richness or H’, calculated on each replicate, eliminated the intrasubstrate variability