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International audience; Coastal and estuarine marshes have been intensively dyked in Europe, with > 15,000 km2 of poldersa. Climate change scenarios forecast an elevated risk of marine submersion and flood hazards. The cost of dykes management in such hazardous environment justifies an increasing interest towards nature-based (NB) solutions. The restoration of natural flood expansion zones is one of those NB solutions retaining some managers interest. Such restoration can also promote marsh ecological functionalities, that serve many other regulation and cultural services for human societies.

International audience; Poster sur la seconde publication de thèse d'Alexis Paumier.

International audience; The database identifies all technical data related to sampling methodologies (fishing techniques, conditions and dates), as well as characteristics of the samples collected (taxa, fish abundance and weight, and individual length and morphometric dimensions). The data can potentially be used to: describe nekton assemblages characterizing dyked marshes and natural intertidal (natural marshes and mudflats) and subtidal areas in a macrotidal estuary; compare nekton assemblages among anthropized, restored and natural habitats within the same estuary; study the temporal dynamics of nekton assemblages in tidally restored marshes; study the size distribution of several species (e.g. Liza ramada, Dicentrarchus labrax, Pomatoschistus microps, Palaemonetes varians, Palaemon longirostris) within diked and other intertidal habitats of the Gironde estuary; study length-weight relationships of multiple fish and macrocrustacean species.

International audience; Harmful cyanobacterial blooms are a major threat to freshwater ecosystems globally weighing down the Good Environmental Status of waters and risk for human health. Biosensors are a highly promising technology that can produce near real-time measurements that could be used by early warning systems safeguarding human and freshwater ecosystem health. We developed a rapid, sensitive, simple and economical test to identify and daily monitor the blooms of potentially toxic cyanobacteria in aquatic environments based on their genetic identity. This innovative solution comes in a colorimetric biosensor format to quickly and efficiently monitor and sustainably manage the contamination risks of potentially harmful cyanobacteria. The biosensor is a genus-specific ribosomal RNA/DNA probe-based assay of potentially toxic genus and is calibrated to equivalent cell numbers. Here we present the field validation tests results performed in a recreative bathing area in south Paris concerning the detection of Microcystis at different sampling points during summer 2017 campaign. The validation was performed by taxonomic cyanobacteria cell counting present in the samples.

International audience; Large lakes of South-Western France are largely impacted by human activities and constitute an important touristic place during summer. Consequently, these lakes have bathing areas regularly monitored for public health. Regulation impose biological monitoring, especially for cyanobacteria that could be potentially toxic. However, analyses carried out in laboratories generate a long delay of response (36 hours) damaging to sanitary safety and leading to important financial costs. The present work, carried out between scientists and managers, proposed to reduce this delay and to limit the costs by modifying the monitoring and alert decision tree with the use of a fluorimetric field probe. Thus, we analyzed 182 water samples from 3 lakes (2012-2013), and compared in situ field probe values with lab's counted cells. We then adapted a decision tree, based on thresholds of cyanobacteria biomass (chlorophyll-a equivalent) instead of the number of counted cells. This new decision tree provides at least the same safety level and is, sometimes, more precautionary than the regulatory method. This new method need however to be tested for other lakes with different cyanobacteria biomass, but provide encouraging results for bathing areas management and is already used for management of lake beaches of the Landes region.

Fatty acids are essential elements for the structure of biological membranes and for the storage of metabolic energy. They are used as a source of energy by metabolism at each trophic level, making fatty acids biochemically and physiologically important compounds (Neves et al. 2015). In the trophic chain, many fatty acids are only synthesized by microalgae and bacteria before being transferred via herbivorous invertebrates to fish and ultimately to humans (Arts et al. 2001). For example, highly unsaturated fatty acids (HUFA) such as eicosapentaenoic acid (EPA; C20:5n3), cannot be synthesized de novo or in insufficient proportions by animals (Saito and Aono 2014). That is why fatty acid analysis is commonly used to study trophic interactions in food chains. Generally, microalgae with a high proportion of EPA, such as diatoms, are an excellent source of food for animals but the concentrations of these different fatty acids can vary according to different environmental parameters including temperature, and may be affected by pesticide exposure (Brett et al. 2006, Robert et al. 2007, Burns et al. 2011, Li et al. 2014, Filimonova et al. 2016). The aim of this study is to investigate the impact of two herbicides combined to a 3°C-temperature increase on diatom's fatty acids and photosynthesis. To address this issue, two model freshwater diatoms (Gomphonema gracile and Nitzschia palea) were exposed to two herbicides, with two different cellular targets, at high concentration (diuron and s-metolachlor, C=10 µg/L) and two temperatures (T1=17,5 °C and T2=20,5°C). After a 1-week exposure, the analysis of photosynthesis was carried out by PhytoPAM measurements, and fatty acid composition of diatom cultures was determined by gas chromatography. For the control samples, the photosynthesis increased with the temperature for the both species mainly for Gomphonema gracile. Concerning the fatty acids composition of the both species, saturated and monounsaturated fatty acids decreased with temperature while polyunsaturated fatty acids increased. The 3°C increase in temperature enhanced the toxicity of diuron towards the photosynthesis of both species, while it reduced the effect of S-metolachlor for Gomphonema gracile. Fatty acids analysis are still ongoing. Our results highlight contrasting effects of a moderate increase of temperature on the toxicity of pesticides towards diatoms, at the physiological (photosynthesis) and structural (fatty acid content) levels.

International audience; The increasing world demand for metals is leading to a consequent increase of metallic element mobilization in aquatic systems. Although the effect of metals on freshwater ecosystems is well documented, studies on the impacts of tetravalent metals are very scarce. Zirconium (Zr) is a tetravalent non-radioactive element for which the global demand has been increasing steadily in the last decades. Benthic microorganism communities (periphyton) have shown good potential as a biomonitoring tool to assess metal exposure of aquatic organisms. In this work, the effect of Zr on periphyton biodiversity and biochemistry was investigated to apply this tool to zirconium and other tetravalent metals contamination assessment and to better understand their potential impacts on aquatic ecosystems. Glass slides were immerged in a pond in Cestas (near Bordeaux, France) for one month to be colonised by periphyton. They were distributed in 3 aquaria containing a synthetic culture medium (Dauta, 1982) and effective concentrations of 0.2 ± 0.1 nM (C0), 0.5 ± 0.3 nM (C1) or 2.9 ± 0.3 nM (C2) of Zr (n=3). One slide per section was sampled after 1, 2 and 4 weeks of exposure for subsequent analyses: dry weight, chlorophyll pigments fluorescence, photosynthetic activity, microscopic microorganism identification, polysaccharide and protein contents. Biomass, proteins, polysaccharides and diatoms abundance increased significantly showing the growth of the biofilm during the experiment. No significant Zr exposure effects were observed on biomass, proteins, polysaccharides contents but their productions appeared to be slightly lower in C1 and C2 at t2 and t4. Diatoms growth rate in the C2 condition was significantly lower than in C0 and C1. Results obtained by pigments fluorescence measurements showed significant cyanobacteria decrease in the C2 condition over the exposure time as well as the brown algae between t2 and t4. Principal response curve (PRC) analysis showed significant changes over time of micromeiofauna composition between the reference (C0) and the C2 condition. Ciliates were less impacted by Zr exposure than flagellates which tended to disappear in the C2 condition. Biofilm microorganisms play a wide role in major ecosystem processes. Regarding these results, Zr exposure can impact the periphyton microorganisms composition which could disturb periphyton key functions. A better understanding of effects of metals on micromeiofauna would improve risk assessment of metallic exposure in aquatic ecosystems.

International audience; French large rivers are impacted by multiple stressors (e.g., chemical and morphological disturbance, hydrological regulation, eutrophication, and climate change), which can greatly influence the evolution of the macrophyte communities. Recent floristic and environmental surveys were performed on different stations of two large rivers in France (Rhone River and Garonne River). Such monitoring work was very useful to analyze the spatial and inter-annual dynamics of the macrophyte communities in interaction with abiotic factors (temperature, flow, nutrient, etc.). The main goal of this study is to determine the main environmental factors triggering the annual growth, abundance and diversity of the macrophyte community. Our results showed that higher water temperature during the growing season (e.g., spring) were significantly correlated with the macrophyte abundance and especially the increasing abundance of exotic species. Variations of river flow also affected macrophyte abundance but was modulated by the intensity, duration, and seasonality of flood events. Our study highlights the need for long-term monitoring data to determine the spatial and temporal evolution of macrophyte communities related to environmental changes such as eutrophication and temperature rise.

/ Les méthodes d'évaluation de l'état écologique des cours d'eau mis en oeuvre en application de la Directive européenne sur l'eau se basent sur une liste taxinomique assortie de l'abondance de chaque taxon. Les opérateurs en charge de l'acquisition de ces résultats hydrobiologiques dans les réseaux de surveillance commettent des erreurs d'identification, liées à leur niveau de compétence et d'expérience, à la difficulté de détermination inhérente à certains groupes, à la variabilité morphologique des taxons aquatiques, à la présence de taxons rares dans certains relevés. Ces erreurs de détermination ont un impact sur les indicateurs calculés à partir de ces listes. Quel est l'impact exact sur ces indicateurs ? Sur l'évaluation finale de l'état écologique ? Cet impact est-il lié à certains paramètres taxinomiques, typologiques, géographiques ?

To assess the lethal effects of diuron (herbicide) and imidacloprid (insecticide) on ubiquist organisms at the basis of food webs, we performed multispecies toxicity tests using nematode species commonly found in soil and freshwater benthic ecosystems. Diuron and imidacloprid belong to the top 15 of the most frequently detected pesticides in French rivers. Both chemicals show an elevated DT50 (time to 50% degradation) in sediments, about 130 days for imidacloprid and more than 30 days for diuron. A standardized toxicity test with Caenorhabditis elegans, a representative for the response of nematode species to toxic stress, showed no significant response to imidacloprid at high concentrations up to 119 mg L-1 regarding growth or reproduction. Diuron inhibited 82% of reproduction success of C. elegans, but showed no significant effect on growth at high concentration (33 mg L-1). Then, we compared the lethal effects of diuron and imidacloprid on eight species of free-living nematodes: Aphelenchoides sp, Caenorhabditis elegans, Pristionchus pacificus, Diploscapter coronatus, Rhabditoides sp, Plectus velox, Plectus opisthocirculus, Plectus acuminatus. Nematodes were exposed in water for 48h to two concentrations (35 and 350 mg L-1 for imidacloprid and 10 and 100 mg L-1 for diuron). Results indicated a low risk of these pesticides to nematodes, as the chemicals did not affect significantly the survivorship at their solubility limit in water for every tested species.

/ La qualité biologique des canaux et rivières naviguées n'est actuellement évaluée que via l'Indice Biologique Diatomées (IBD2007), seul indicateur applicable dans ces milieux soumis à des usages anthropiques réguliers. En 2017, il a été démontré que les valeurs des notes IBD étaient impactées significativement par le gabarit et l'intensité de la navigation dans le bassin Artois-Picardie. Ce travail a été poursuivi en 2018 et amplifié par une étude menée au niveau national. Les notes IBD calculées entre 2008 et 2015 dans les 6 bassins métropolitains ont été rapatriées auprès des Agences de l'Eau, tous réseaux de mesures confondus, et classées en fonction de leur classe de qualité. Les valeurs indicielles ont été confrontées avec différents paramètres, notamment la taille du cours d'eau, et l'appartenance ou non à un réseau navigué (données Sandre et Eaufrance). Un peu plus de 7200 stations ont été répertoriées, parmi lesquelles on ne distingue que 238 cours d'eau navigables (dont 101 canalisés). Sur le jeu de données global (tous cours d'eau) et sur les 8 années de suivi, on constate qu'une majorité de stations est en bon état. On note même une augmentation de la classe très bon état, en particulier depuis 2011. A la même échelle nationale, on constate que les cours d'eau navigués sont globalement en état moyen, et que la navigation a un effet statistiquement significatif induisant une baisse de valeur moyenne de l'IBD. D'autre part, l'influence générale occasionnée par des aménagements physiques de type canalisation, terme très englobant qui peut recouvrir une large diversité de situations, apparaît moins nette sur le maillon diatomique. Afin de mieux spécifier les impacts éventuels liés aux canaux, il serait donc utile d'avoir recours ultérieurement à une description et à une typologie plus fine basée à la fois sur les caractéristiques, sur les usages et sur le fonctionnement hydromorphologique de tels ouvrages. Ce constat d'impact en liaison avec la navigation et la canalisation, usages sociétaux à caractère obligatoire qui présentent des contraintes et nuisances particulières d'exploitation, rapproche les masses d'eau concernées de MEFM (quel que soit leur statut actuel décidé par chaque Agence de Bassin) et plaide en faveur de la mise au point d'un système d'évaluation spécifique pour ce type de masses d'eau, différent de celui en place pour les cours d'eau habituels et visant à l'atteinte du bon potentiel écologique.

Deformities in diatoms are increasingly used as an indicator of toxic stress in freshwaters. However, the percentage of deformities alone often fails at highlighting the magnitude of toxic exposure. An approach combining the assessment of deformities coupled with information on their severity could improve the sensitivity of this biomarker. With the aim of quantifying the deviation from the normal form, we tested the applicability of geometric morphometry to evaluate the degree of deformities in different diatom species. We used photomicrographs of normal and deformed specimens from laboratory cultures of Gomphonema gracile, Nitzschia palea, and of Achnanthidium minutissimum from field samples collected along a gradient of toxic contamination. The geometric morphometry approach is based on several landmarks positioned on the outline of the diatom valves. Statistical analyses were conducted based on the geometrical coordinates of the landmarks. This technique allowed to discriminate between normal and deformed individuals. The geometric morphometry approach revealed a gradient in the intensity of the deformities observed on Gomphonema gracile and Achnanthidium minutissimum, in-line with a priori, visually determined (subjective) classifications. A relationship between the degree of deformity in Achnanthidium minutissimum and a gradient of zinc contamination was found. In contrast, the approach failed to obtain good fit for Nitzschia palea individuals because deformities in this species were more variable in terms of their location on the valves. Geometric morphometry provided encouraging results to objectively quantify the intensity of diatom deformities affecting valve outline, and could easily be implemented in further automatic diatom identification developments.

/ Située sur l'Aire d'Alimentation de Captage (AAC) de Villevieux (eau potable de la ville de Lons-le-Saunier, Jura), la Madeleine est une rivière fortement exposée aux pesticides agricoles provenant de cultures diverses (céréales, maïs, colza, vigne). Le service des eaux, gestionnaire de l'AAC, a mis en place entre 2011 et 2016 un suivi de la qualité chimique des eaux des rivières du captage par prélèvements ponctuels, qui a notamment soulevé des interrogations sur la contamination des eaux dès les sections amont de ces rivières, et sur la contribution des différents affluents. Néanmoins, un diagnostic précis de la contamination en pesticides est difficile à réaliser à cause du manque de représentativité temporelle des prélèvements ponctuels réalisés, et devant l'absence de prise en compte de la toxicité potentielle associée. C'est ainsi qu'au printemps et à l'automne 2017, périodes propices aux transferts de pesticides vers les cours d'eau, des outils de diagnostic de la qualité chimique et biologique ont été déployés pendant un mois sur 3 stations de la Madeleine de façon à intégrer les apports à la contamination de deux principaux affluents. En plus de la variabilité saisonnière, une variabilité temporelle plus fine a été évaluée par le déploiement de certains outils sous forme de séquences de plusieurs tests (séquences d'un mois constituées de 4 ou 2 tests de 7 ou 15 jours respectivement). Le diagnostic a été réalisé à l'aide : i) d'échantillonneurs passifs (Tige Silicone Polaire et POCIS permettant l'analyse de 70 substances actives ou métabolites de pesticides) : placés dans le cours d'eau, ils permettent un échantillonnage en continu, et améliorent ainsi la représentativité de la mesure de la qualité du milieu par l'obtention d'une concentration intégrée sur le temps d'exposition de l'outil (7 ou 14 jours). ii) de la bioviosurveillance active qui permet de mesurer des effets toxiques aux échelles moléculaires et individuelles chez des organismes Gammarus fossarum transplantés (encagements). Les marqueurs choisis ont été la survie, l'inhibition de l'activité acétylcholinestérase, le taux d'alimentation et les marqueurs de reproduction. Nous présenterons dans ce poster les premiers résultats de ces expérimentations complémentaires qui mettent en évidence des variabilités spatiales et temporelles (hebdomadaires et saisonnières) de la contamination en pesticides et de l'impact toxique, et permettent ainsi de compléter le diagnostic de la qualité de l'eau de la Madeleine.

/ A partir d'une adaptation de la méthodologie de biosurveillance active gammare qui permet de mesurer la contamination chimique en rivière, la contamination chimique biodisponible à pu être mesurer sur 10 stations de deux plans d'eau aquitain. Le poster décrit les étapes du transfert de la méthodologie des rivières au plans d'eau et présente les résultats préliminaires.

International audience; Diuron-induced photosynthesis inhibition of freshwater biofilms and subsequent EC50s (half maximal effective concentrations) are determined using a 3-hour exposure in average. However, given the known rapid action of diuron, earlier responses can be expected. In this study, we performed different time-response experiments to confirm the short time lag for diuron to reach its cellular target, and to assesss whether time-response curves (i.e. photosynthesis inhibition as a function of time, when diuron exposure is kept constant) can improve the assessment of short-time (pulse) pre-exposure to diuron. Our results demonstrated that: i) diuron reaches its cellular target in a very short time-span (100µg.L-1) to 7:20 minutes (exposure to EC25). We were also able to demonstrate previous pulsed (3 hours) exposure to increasing concentrations of diuron (0, 5 and 50µg.L-1) using time-responses curves, providing a new, easy-to-implement, method to assess short-term exposure to PSII inhibitors based on community photosynthesis.

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASARE; International audience; Ensuring traceability of field experimental data or laboratory sampling data to conduct reproducible research is a challenge at the present time. Between the time when geolocalized specimens (biotic or abiotic) are taken, and the time the resulting data ends up in analysis published within a study, many manual operations take place and may generate errors. The French LTSER have joined forces at the national level to propose a solution as generic as possible to this problem of monitoring of the samples and the data associated with them. Compared to existing solutions (such as Laboratory Information Management Systems), we target a robust labeling solution adapted to outdoor working conditions, with the management of stocks and movements of samples. We designed and realized a prototype tested from end to end, using an open source software (https://github.com/Irstea/collec), cheap Zebra printers (mobile or not) and raspberries as devices. This solution provides sufficient flexibility for the wide variety of existing protocols. Its strength is the record of all contextual data associated with the samples, which constitute important parameters of the subsequent analyzes. At last, not only traceability is guaranteed, but also a gain of time and a rationalization of the storage of samples that will induce a return on investment.

International audience; Climate change by altering spatio-temporal distributions of suitable habitats leads to modifications in a multitude of species ranges. In recent years, the ability of species to physically adjust to the changing climatic conditions is of growing concern. We developed a generic trait-based method to assess the ability of species to explore new suitable habitats under climate change. Anadromous fish populations of the northern Atlantic were chosen as a suitable application case due to their high variability in terms of migratory behavior and degree of philopatry. The calculation of an Exploratory Potential Index (EPI) relies on a formal framework and a participatory procedure adapted from the Analytical Hierarchy Process (AHP) theory. It combines independent relevant life-history traits and ecological attributes into a single numeric value and permit to gather expert opinion by decomposing a complex issue into a hierarchy of more easily comprehended sub-problems through pairwise comparison matrices. Straying, earliness of first maturity, body size at first maturity, Distance covered to access feeding grounds and the reproduction strategies were identified by the expert. Results allow to identify different dispersal strategies an support strong differences in the ability to explore potential suitable habitat among anadromous fish. Even though they have contrasted life cycles, Morone saxatalis, Acipenser oxyrinchus and Alosa mediocris outperformed most of the species, while other species as Acipenser brevirostrum demonstrated had the lowest scores. Broader applications of the EPI would help to identify regions acting as potential sources of migrants and thus of priority for conservation biologists and resources.

International audience; European sturgeon (Acipenser sturio) is an anadromous fish that breeds in rivers and which was previously found on most coasts of Europe. The last population of this species, nowadays listed as critically endangered, is reproducing in the Garonne basin near Bordeaux, south-west of France. In order to avoid extinction, the applied strategy since 1985 has been to release young fish into natural environment. These young individuals resulted from the assisted reproduction of wild and/or captive mature individuals. Recently recorded data in the Garonne basin show that in some sectors, where juveniles are likely to growth, summer temperatures have reached very high levels and water column has been hypoxic. Therefore, the combined influence of these factors on the young developmental stages needs to be assessed. The main goal of our project is to provide key information for improving the management of young fish release, especially age at release and release sites that maximize the fish survival. In this purpose, we will first calibrate a standard DEB model, based on the large dataset provided by the long term ex-situ stock breeding in our research institute. This model will firstly be used to evaluate the effect of temperature and oxygen on the survival rate of the first developmental stages. Other aspects of the life cycle will also be investigated, such as the link between maturity and the migration dynamics of the species and the impact of environmental conditions on eggs quality. The last part of our project will consist in the implementation of the standard DEB model within a pre-existing Individual Based Model (IBM) of the sturgeon population dynamics in the Garonne basin. This methodology will allow us to identify which individual traits are determinant in order to maximize the reinforcement of the sturgeon population in this basin.

/ Les sources hydrothermales terrestres et sous-marines sont nombreuses et de fonctionnement varié en Guadeloupe, du fait de l'activité volcanique et de la nature altérée et fracturée du massif. Bien que les systèmes hydro-thermaux du massif de la Soufrière fassent l'objet d'un suivi physico-chimique depuis les années 1960 dans le cadre de la surveillance de l'activité volcanique réalisée par l'Observatoire volcanologique et sismologique de la Guadeloupe, les compartiments biologiques des sources hydrothermales de la Guadeloupe n'ont que très peu été étudiés. Sans prétendre à l'exhaustivité, une première étude a permis d'explorer les principaux compartiments constituant le biofilm qui se développe dans et à proximité immédiate des sources guadeloupéennes : les diatomées, les bactéries, les cyanobactéries ainsi que les Archées. Dans un second temps, l'étude des diatomées des sources hydrothermales de la Martinique est venue compléter les données acquises en Guadeloupe. En ce qui concerne les diatomées, aucune étude naturaliste n'avait eu lieu depuis la mission P. Allorge en 1936, qui avait permis à Manguin et Bourrelly de décrire plusieurs taxons dont certains rarement observés depuis, par exemple Navicula guadalupensis Manguin in Bourrelly & Manguin et Navicula thermophila Manguin in Bourrelly & Manguin. Cette dernière est maintenant attribuée au genre Chamaepinnularia : C. thermophila (Manguin) C.E. Wetzel & Ector (2016). Compte tenu de l'évolution de la taxonomie, et à la lumière de nos observations réalisées en microscopie électronique, Navicula guadalupensis devrait maintenant appartenir au genre Microcostatus. Une espèce du genre Halamphora est potentiellement nouvelle pour la science. Ces études ont permis de mettre en évidence la présence d'autres micro-organismes photosynthétiques ou non inféodés à ces conditions environnementales extrêmes et ont également révélé des interactions biologiques et peut-être biochimiques originales (Cyanobactéries du genre des Plectonema associées à des bactéries sulfo-oxydantes du genre Thiomicrospira), ce qui confirme que les sources hydrothermales des Antilles françaises restent un laboratoire naturel encore à explorer.

International audience; As primary producers, microalgae can be directly affected by herbicides. These organisms can also be impacted by other environmental elements such as the dissolved organic matter (DOM), that may also interact with pesticides. Indeed, MOD can affect pollutant transport, fate, biodegradation, bioavailability, and toxicity on organisms. Therefore, the present study aimed to investigate whether natural DOM influence the toxicity of three herbicides (irgarol (I), diuron (D) and S-metolachlor (S)), single and in mixture, on two marine microalgae, Chaetoceros calcitrans (Cc) and Tetraselmis suecica (Ts). After 6-day exposures to each herbicide (I0.05 and I0.5 µg.L-1; D0.05 and D0.5 µg.L-1; S0.5 and S5 µg.L-1) and to mixtures (M1: I0.05+D0.05+S0.5 and M2: I0.5+D0.5+S5), the effects of herbicides were assessed on growth (doubling time TD), photosynthetic yield (Yeff), reactive oxygen species presence and intracellular relative lipid content. For each condition, two sets of triplicates were run: one with natural DOM added to the culture media, another without DOM. Without DOM, I0.5 and M2 significantly affected almost all parameters with similar trends in both species: an increase of TD by more than twice (+125% and +129% for Cc and Ts respectively, at I0.5), a decrease of Yeff (approximately 30%) and a decrease of the relative lipid content. The M2 impacts observed in Cc were similar to the effects induced by irgarol at 0.5 µg.L-1, however a higher toxicity was shown for Ts (+167% for TD), suggesting a possible synergistic effect of mixture. When DOM was added in the culture media, significant effects were also observed with I0.5 and M2 conditions for both species: while the effects of I0.5 in TD of Cc were decreased (+101%), they were strongly enhanced for Ts (+178%), as were the effects of M2 (+298%). The presence of DOM decreased the herbicide toxicity for Cc whereas toxic effects were increased for Ts. These results may partly be due to the complexation between DOM and herbicides, leading to a lower bioavailability of herbicides. However, the difference in toxicity between the two species remains to be explained. Analysis of herbicide concentrations, dissolved organic carbon concentration and DOM, which are still ongoing, will help to improve the understanding of interactions between microalgae, herbicides and DOM. Finally, this study demonstrates the importance to consider DOM as a major factor possibly involved in toxicity modulation in the environment.

/ Une étude des assemblages diatomiques des sites Aïn Bou Rkhiss et Aïn Kibrit, deux sources qui prennent naissance dans le lit de l'Oued Merguellil, et Aïn Ben Ali, un puits situé dans les massifs adjacents (District de Kairouan, Tunisie Centrale), a été menée en décembre 2014 et février 2016. Quelques paramètres physico-chimiques ont été mesurés sur ces sites lors des prélèvements diatomiques. Les deux sources Bou Rkhiss et Kibrit sont proches l'une de l'autre, mais ont des caractéristiques et des usages bien distincts (p. ex., respectivement, eau potable à usage domestique et eau sulfureuse, se mélangeant naturellement à l'eau de l'oued qui sert à l'irrigation), alors que l'eau du puits Ben Ali est à usage domestique et pour les troupeaux. Les objectifs de cette étude visaient à comparer les assemblages diatomiques de trois points d'eau proches géographiquement, de caractériser leur statut écologique et tester la qualité biologique des eaux à l'aide d'indices diatomiques normalisés en France (IBD, Afnor 2007). Les assemblages de cyanobactéries ont également été étudiés. Nous abordons les origines hydrogéologiques de ces points d'eau, bien que non encore parfaitement identifiées, et nous discutons de deux aspects concernant la façon dont les populations vivant à proximité de ces sources les perçoivent : angoisse d'être privés de leurs droits (Aïn Bou Rkhiss est considérée par les populations comme un approvisionnement en eau sûr et de très bonne qualité) et connaissances locales de la circulation des eaux souterraines. Les qualités d'eaux estimées à l'aide de l'IBD reflètent parfois des situations plus pessimistes que celles attendues par les utilisateurs locaux. Les causes sont à rechercher dans les limites de cet indice : méconnaissance des situations de référence, inadéquation de ces méthodes conçues pour des eaux douces européennes sans prise en compte des formes tropicales ou subtropicales. En outre, la juxtaposition dans les cortèges de diatomées de formes oligotrophes, (Achnanthidium, Crenotia, Brachysira), saprophiles (Nitzschia spp.) ou halophiles dans les sources sulfureuses (Entomoneis, Pleurosigma, Haslea, Tabularia,...) entraîne une certaine variabilité spatiale et temporelle des estimations en fonction des dominantes, qui affecte la fiabilité du diagnostic. Les résultats acquis sur ces points d'eau permettent de nuancer l'appréciation des riverains, mais les calculs devraient être affinés par une prospection plus large et des comparaisons avec d'autres sources tunisiennes de référence.

International audience; European eel: features and distribution, building the optimality model GenEvEel 1.0, first results.

International audience; Dans le cadre d’une étude sur la mise en place d’un nouvel indice de bio évaluation des rivières de Nouvelle-Calédonie, une étude des diatomées benthiques a été initiée fin 2012. La flore locale a déjà fait l’objet de plusieurs publications, essentiellement Moser et al. (1995, 1998) et Moser (1999) qui décrit le pays comme les « Galapagos des diatomées », en raison du contexte géologique particulier et du fort taux d’endémisme rencontrés (environ 40%) sur cette île du Pacifique. L’étude d’une cinquantaine de stations prélevées en saison sèche et en saison humide entre 2012 et 2014 (soit 4 campagnes), réparties sur les 6 hydro écorégions que connait la Grande Terre a révélé des taxons posant ou ayant posés des soucis de détermination. Ce poster invite le lecteur à partager nos interrogations.

International audience; Grab sampling may be scarcely adequate to evaluate the impact on surface waters of pesticide used in agriculture because of its poor spatiotemporal representativeness compared to the high variability of the contamination patterns. Indeed, it is still not easy to link the effect of agricultural practice changes to water quality at the catchment scale. Furthermore, biological indicators may also be useful in addition to pesticide concentration determination to evaluate their impact on ecosystems. In this way, the contribution of new integrative tools has been evaluated. Passive samplers and biological indicators have been applied together at the catchment scale so as to identify their coherence and complementarity. The tested chemical tools are the passive-SBSE (Stir Bar Sorptive Extraction) dedicated to hydrophobic to moderately hydrophilic compounds and the POCIS (Polar Organic Chemical Integrative Sampler) dedicated to hydrophilic compounds. As concerns biological approach, it consisted in the in situ deployment of i) caging methodology with a highly ecological relevant amphipod species, Gammarus fossarum, coupled to the measurement of toxicity markers (acetylcholine esterase inhibition, feeding rate) and ii) the study of microbial and macro-invertebrate communities (measurement of leaf decomposition rates) as well as phototrophic periphytic communities (measurement of Pollution Induced Community Tolerance). These tools have been applied during june 2014 (corresponding to vineyard and corn period of application) in two contrasted agricultural catchments. The Ardières basin situated in the Beaujolais region (France) is submitted to viticulture pressure and a marked pesticide contamination has already been highlighted. Three measurement stations have been chosen so as to search for a contamination gradient from upstream to downstream. The Coise basin is located in the Monts du Lyonnais (France) in a zone of mixed farming breeding with a predominance of meadows, corn and cereals. Three measurement stations have been selected on three sub-catchments corresponding to differentiated pesticide use. In total, 49 pesticides (28 herbicides, 9 fungicides and 12 insecticides) have been analyzed as well as potential confusing parameters (metal(oïd)s, nutrients, temperature, luminosity, water flow). Results show the high coherence of chemical and biological tools responses. All of them were able to reflect the spatial contamination gradients as well as the specific contamination and impact associated to each agro-pedo-climatical context. A weekly exposure also permitted to take into account the temporal variability of the contamination according to flood occurrence. Finally, their sensitivity, reactivity and integration capacity make these tools relevant and promising to assess agricultural pesticide impact on surface water in addition to grab sampling.

International audience; This poster was presented during the AFH conference in June 2015. It presents the methodology based on AHP developped. It aims to estimate an Exploratory Potential Index for anadromous fish of the north atlantic Ocean. It combines several independant variables and experts opinion in order to provide a single composite value.

/ Biodiversité et vulnérabilité des communautés de diatomées benthiques en milieu lotique.

International audience; The assessment of compositional differences between bryophyte communities from different fluvial regions should ideally be achieved using biologic and environmental field data from standardized pan-European surveys. Since aquatic bryophyte communities result from interactive effects of local environmental filters, larger climatic filters and anthropogenic stressors, we aimed to explore the compositional segregation of bryophyte communities across three Mediterranean regions (Environmental Stratification of Europe; Metzger et al. GEB 14: 549-563). We used floristic data collected for intercalibration purposes under the EU Water Framework Directive and data from River Habitat Survey of 474 Mediterranean sites (99 South, 246 North; 129 Mountains). Applying TWINSPAN, SIMPER and ANOSIM analysis, we compared assemblages between Mediterranean climatic regions and identifyed indicator taxa. TWINSPAN revealed four distinct groups after two divisions which do not strictly separate sites according to climatic regions, indicating other underlying ecological compostional determinants. Bryophytic composition reveals that sites of different climatic zones share hydrologic and geomorphologic features, creating niche for shared core taxa and other region-specific taxa responsible for each region singularity. This results reinforce the importance of fluvial landscape heterogeneity conservation for the sustainability of European aquatic bryophyte richness and diversity.

International audience; Developing macrophytes-based methods for assessing the ecological status in rivers needs to deal with different analyze scales: floristic data are recorded at the site scale while the anthropic pressures are defined at large scale of catchment area. Thus, the response of the macrophytes communities cannot be directly explained by the catchment features. To focus on the hydromorphology highlights the needs of multi-scales approach. Indeed these environmental parameters cover functioning (hydrology) and characteristics (substrate, river shape) at nested scales. The search for sensitive macrophytes metrics assessing the impact of environmental parameters, especially for the hydromorphological aspects, were tackled by 1/ determinate the relationship between population and habitat at the site scale, 2/ understand the links between large-scale pressure and local morphological feature, 3/ analyzing the correlations between both scales and biocenosis characteristics. This approach was undertaken using the French WFD biological monitoring (over 4000 surveys). A set of biological (IBMR, growth forms, vegetal cover) and environmental metrics was defined and tested as integrating meta-data. A PLS modeling distinguishing pressures at catchment, reach and site scales was used in order to respect the hierarchical spatial organization. This multi-scalar method was developed to identify and quantify the biotic response through these different scales.

/ La pollution par l'arsenic est un problème mondial. Les eaux (de surface et souterraines) en sont la voie principale de contamination. Nous avons mené une expérience visant à étudier les effets de ce métal sur les descripteurs fonctionnels et structurels des communautés de diatomées benthiques (Barral-Fraga et al., 2015). Plus précisément, nous avons analysé les changements dans la photosynthèse et dans la structure des communautés de diatomées (abondances relatives des espèces), la densité de chaque espèce rapportée à la surface échantillonnée, et la taille cellulaire de chaque espèce. Les dimensions réelles de chaque individu ont été mesurées, permettant d'évaluer le biovolume moyen des espèces dominantes, ainsi que la contribution de chaque espèce au biovolume diatomique total. Ainsi, en combinant des descripteurs écologiques et écotoxicologiques, nous nous attendions à mieux caractériser l'impact toxique de l'arsenic sur le périphyton. Bien qu'aucune différence significative dans les densités de diatomées n'ait été observée entre biofilms exposés ou non à l'arsenic, nos résultats ont montré une évolution de la structure spécifique de la communauté diatomique. Nous avons identifié 52 taxons de diatomées, Achnanthidium minutissimum (Kützing) Czarnecki étant la plus abondante (77% en abondance relative moyenne): 75% dans les témoins et 79% en cas de contamination, indiquant sa tolérance à l'arsenic. En outre, l'arsenic réduit la richesse spécifique (p = 0,051) et le biovolume cellulaire moyen (p = 0,003). Le biovolume de certaines espèces est également modifié, avec une tendance générale à la diminution de la taille des individus exposés à l'arsenic ; bien que l'inverse soit observé pour les Fragilaria (selon les espèces, plus nombreuses en nombre que dans les témoins, ou de dimensions individuelles plus grandes au sein de l'espèce). En conclusion, les différents paramètres étudiés ont été affectés par l'exposition à l'arsenic. Etant donné les concentrations nominales de cette expérience (130 μgAsV/L), ces résultats remettent en question les normes de qualité environnementales pour l'arsenic, qui sont plus élevées.

/ Les approches décrites dans ce manuscrit s'inscrivent dans un cadre intégrant écologie, écotoxicologie et écophysiologie, à différentes échelles d'organisation du biofilm, du sub-individu à la communauté.

International audience; Two large French rivers (Rhône and Vienne rivers) are impacted by multiple stressors (e.g., nutrient enrichment, hydrological regulation, hydropower schemes, climate change), which can greatly influence the evolution of the macrophyte communities. Environmental monitoring including floristic data were performed on the Rhône River close to St Alban and on the Vienne River at Civaux, since 1985 and 1997, respectively. Such monitoring work was very useful to analyze the inter-annual dynamics of macrophyte communities in both rivers. Classification and ordination analyses of these data showed a significant inter-annual evolution in the macrophyte communities, during which some key moments of the population structure changes have been identified. On the Rhone River, the major changes in the floristic data are correlated with environmental changes over the years such as the decrease of nutrient concentrations and the increase of water temperature during the growing period. Such changes induced the first appearance of invasive species such as Elodea nuttalli in 2003, during a major heat wave. On the Vienne River, our results showed a major community shift in 2000 with the successive appearance of several species including Myriophyllum verticillatum. In 2008, the population showed another shift with the appearance of Myriophyllum spicatum and invasive primrose (Ludwigia sp.).; Le Rhône et la Vienne, deux grands cours d'eau français, sont soumis à de multiples pressions (enrichissement nutritif, régulation hydrologique, aménagement hydraulique, changement climatique) ayant un rôle majeur dans l'évolution des communautés de macrophytes. Un suivi environnemental sur le Rhône à St Alban et sur la Vienne à Civaux a permis l'acquisition de données floristiques, respectivement depuis 1985 et 1997, constituant une base de travail pertinente pour analyser la dynamique interannuelle des communautés. La classification et l'ordination de ces données ont mis en évidence un gradient d'évolution interannuelle dans les peuplements, au cours duquel des moments clés de la structuration du peuplement ont été identifiés. Sur le Rhône, une forte concordance de ces évolutions avec la diminution de concentration de certains éléments nutritifs et une augmentation de la température de l'eau durant la période végétative a été observée. Cela s'est notamment caractérisé par l'apparition d'espèces exotiques envahissantes telles qu'Elodea nuttalli en 2003, année d'une importante canicule. Sur la Vienne, les analyses ont montré une rupture remarquable dans la communauté en 2000 avec l'apparition successive d'espèces telles que Myriophyllum verticillatum. En 2008, le peuplement a subi une nouvelle modification majeure liée à la présence de Myriophyllum spicatum et de Jussies (Ludwigia sp.).

International audience; Irgarol 1051 and diuron are two booster biocides commonly used in antifouling paints. They target directly the photosystem II by inhibiting the electron transfer between QA and QB. As photosystem II structure does not vary much between different plant organisms and algae, numerous unwanted targets can be affected in case of environment contamination. The single and combined effects of these two compounds were investigated towards two marine phytoplankton species, Chaetoceros calcitrans (a single “wild” strain WC) and Tetraselmis suecica (two strains: “wild” (WT) and diuron-resistant mutant (MT)). The effects on growth, photosynthetic yield, reactive oxygen species presence and intracellular relative lipid content were assessed after a 6-day exposure to a range of concentrations from 0.01 µg.L-1 to 0.5 µg.L-1 for irgarol and from 0.5 to 5 µg.L-1 for diuron. Diuron induced a significant effect at 5 µg.L-1 for WT and WC, with an increase of their doubling time by 168% (± 20) and 14% (± 2) respectively. DCFH-DA fluorescence related to ROS presence showed an increase by 94% (± 3) compared to the control for WT. The diuron-resistant strain MT showed no significant effect at the end of the 6-day exposure to diuron 5 µg.L-1. Micro-algae exposure to 0.5 µg.L-1 irgarol also showed significant results, as doubling time increased by 54% (± 4) for WC and by 19% (± 2) for WT after a 6-day exposure. Photosynthetic yield decreased by 25% (± 0) for WC and by 17% (± 1) for WT. The mutant strain was greatly inhibited at 0,5 µg.L-1 irgarol with an increase of 63% (± 2) and 60% (± 8) of doubling time and DCFH-DA fluorescence, respectively. Finally, a 6-day exposure to a mixture of diuron and irgarol was performed, but results are still being acquired. The sequencing of the psbA gene of mutant strain is still ongoing. This study demonstrates the high toxicity of these two biocides to marine phytoplankton. It also demonstrates that resistance to diuron does not necessarily enables resistance to another PSII inhibitor. This highlights the need to monitor the fate of these two compounds in the environment, especially for irgarol, since it’s still authorized in many European countries.

/ Les variations de taille (biovolume) et de forme des diatomées peuvent révéler des perturbations de la biocénose. Le Flowcam® (cytomètre couplé à de l'acquisition d'image, classification automatique) a été utilisé afin d'estimer les capacités de l'appareil (x20) à déterminer les tailles et les biovolumes de diatomées. Des comparaisons entre des mesures effectuées au microscope optique et au flowcam ont été réalisées sur des diatomées en culture. Deux morphotypes de Gomphonema gracile (normal et tératogène) dans deux états (vivantes et après digestion H2O2) ont été utilisés. Les performances du Flowcam ont été estimées à partir de ces quatre échantillons, les limites et précautions d'utilisations ont été répertoriées. Les images obtenues doivent être validées systématiquement par un observateur, car de nombreuses photos ne sont pas exploitables pour permettre d'obtenir des mesures fiables des dimensions. Les photos exploitables permettent d'obtenir une qualité variable de l'estimation des dimensions réelles (mesures microscopes), en effet : •les longueurs sont non significativement différentes pour 30% des échantillons. Le solde des mesures (70%) indique une sous-estimation de l'ordre de 5 à 7% (longueur de l'ordre de 31 µm) et de 7 à 12% (longueur de l'ordre de 18 µm). •les largeurs sont non significativement différentes pour 70% des échantillons. Le solde des mesures (30%) indique une sur-estimation de l'ordre de 8 à 14% (largeur de l'ordre de 5 µm). •les biovolumes n'ont pu être calculés car l'estimation de l'épaisseur des diatomées est significativement différente pour tous les échantillons avec une surestimation de l'ordre de 6 à 85%. Cette surestimation augmente avec la diminution de l'épaisseur des diatomées. •Pour combler l'absence d'information concernant les biovolumes. Une comparaison des surfaces des diatomées en vue valvaire a été réalisée, le Flowcam a la possibilité à partir des photos obtenues de calculer la surface occupée par la diatomée. Cette surface a été comparée à celle obtenue par calcul (formule mathématique) à l'aide des mesures effectuées au microscope. Les surfaces sont non significativement différentes pour 30% des échantillons. Le solde des mesures (70%) indique une sous-estimation de l'ordre de 6 à 12%.

The use of fertilizers in agriculture has a well-known effect on river, lake and coastal sea eutrophication. The effect of agricultural pesticides on aquatic ecosystems has been less investigated. Pesticides are transferred to the rivers via soil water runoff and spray drift. The toxicity of pesticides can affect non-target aquatic organisms and thus perturbate ecosystems. Herbicides may be toxic especially for aquatic photosynthetic organisms including algae. Periphytic diatoms are a major component of the biofilm growing at the light exposed surface of immerged substrates. As primary producers they are at the basis of the lotic trophic web. Diatoms have been extensively used as bioindicators of trophic and organic pollution. However, diatom standard indicators fail to properly detect toxic impact of molecules which do not target the photosystem II. The purpose of the study is to evaluate the effect of an herbicide, the metolachlor (a cell division inhibitor, inhibitor of Very-Long-Chain Fatty Acid) on a diatom species isolated from the field (Gomphonema gracile Ehrenberg), exposed to three concentrations of metolachlor (1, 10, 100 µg/L). Assessing metolachlor toxicity is of major concerns, because of its presence at high concentration in rivers. The effects of metolachlor on diatoms were evaluated according to physiological and behavioral parameters. These parameters were analyzed immediately after exposure, and 1, 2, 3, 4 and 7 days post-exposure. Metolachlor did not affect much population dynamics, photosynthesis and ATP content. Though metolachlor did not bioaccumulate in the biota, the mobility parameters provided early responses (on day 3) for all concentrations. These finding demonstrate the importance of use of various parameters and the potential of behavioral descriptors in toxicity assessment.