Microbial communities play a major role in the functioning of ecosystems: they are at the base of the food chain (primary production) and participate in the degradation of organic matter. These communities are also known to respond rapidly to environmental changes. Like macro-invertebrates, they can be used as ecological indicators. Benthic diatoms are the main photosynthetic organisms in this biological community. The relative abundance of the various species is used to calculate an environmental quality index (EQI). Major differences in communities between the upstream and downstream zones were observed when the dams were in place. These differences will change once the dams are removed. As part of the Sélune observatory, pilot stations have been set up along the main course of the Sélune, distributed from upstream to downstream of the hydroelectric dams. Three stations are located in the former reservoirs of the dams, while the other two, known as the reference stations, are outside the area of influence of the former dams (one downstream and the other upstream). At these stations, aquatic biocenoses (including benthic macroinvertebrates, biofilms, macrophytes, etc.) are monitored. Since September 2014, the stations are ideally sampled every month from April to October (7 annual surveys) using artificial substrates (glass slides placed in the water). In addition to the diatom survey (floristic list, IBD calculation), the chlorophyll-a concentration is measured. This layer shows the location of the study sectors used to monitor photosynthetic biofilms and the campaigns carried out.

Ce projet a pour ambition de mettre en place des méthodes qui permettront de suivre le retour des poissons migrateurs emblématiques tels que le saumon ou l’anguille dans la vallée de la Sélune après sa remise en continuité.

Ce projet a pour ambition de mettre au point et d’appliquer une méthode non invasive de suivi des flux de poissons migrateurs dans la Sélune. Le développement de cette méthode repose sur l’analyse d’images et vidéos prises par une caméra hydroacoustique positionnée dans le cours d’eau.

En quelques mots :  Le projet Biomonitoring "Effet des arasements sur les communautés animales et végétales de la Sélune" a pour principal objectif de réaliser un état de référence de la qualité biologique de la Sélune à l’amont et à l’aval des deux barrages ainsi que dans les retenues. Il vise également à identifier les risques (exposition aigüe) pendant les travaux de fixation des boues contaminées de l’Yvrande. Objectifs Répondre aux questions : Comment l'écosystème lotique se restaure-t-il après disparition d'un lac de barrage, et quels nouveaux équilibres écologiques en résultent ? Quels seront les effets des travaux d'arasement sur la qualité des milieux et leurs conséquences sur les biocénoses qui s'y développent ? Méthodes : IBMR ; IBGN ; IBD ; suivi des biofilms ; caractérisation physico-chimique Données :  - Suivi des conditions physico-chimiques (t°c, conductivité, pH...) - Concentration en nitrates, silicates, azote et phosphore total - Suivi des communautés d’invertébrés - Suivi des communautés de phyto- et zoo-plancton, et mesure de la biomasse de phytoplancton - Suivi du biofilm (2015 à 2017) - Suivi des plantes aquatiques (1996) - Relevés floristique des plantes aquatiques (2015, 2017) - Caractérisation toxicologique des poissons de la retenue de Vezins - Analyse des contenus stomacaux (GCA) des poissons

Ce projet compare la mise en place, l’acceptation et le déroulement de projets d’effacements de barrages en France, avec l’exemple de la Sélune, et aux Etats-Unis, où plusieurs cas d’effacements similaires se sont déroulés.

Microbial communities play a major role in the functioning of ecosystems: they are at the base of the food chain (primary production) and participate in the degradation of organic matter. These communities are also known to respond rapidly to environmental changes. Like macro-invertebrates, they can be used as ecological indicators. Benthic diatoms are the main photosynthetic organisms in this biological community. The relative abundance of the various species is used to calculate an environmental quality index (EQI). Major differences in communities between the upstream and downstream zones were observed when the dams were in place. These differences will change once the dams are removed. As part of the Sélune Observatory, the stations are sampled every month from April to October (7 annual surveys) using artificial substrates (glass slides placed in the water). In addition to the diatom survey (floristic list, IBD calculation), the chlorophyll a concentration is measured. This layer gives the IBD and EQR (normalised) index value for a station during a campaign.

Microbial communities play a major role in the functioning of ecosystems: they are at the base of the food chain (primary production) and participate in the degradation of organic matter. These communities are also known to respond rapidly to environmental changes. Like macro-invertebrates, they can be used as ecological indicators. Benthic diatoms are the main photosynthetic organisms in this biological community. The relative abundance of the different species is used to calculate an environmental quality index (EQI). Major differences in communities between the upstream and downstream zones were observed when the dams were in place. These differences will change once the dams are removed. As part of the Sélune observatory, pilot stations have been set up along the main course of the Sélune, distributed from upstream to downstream of the hydroelectric dams. Three stations are located in the former reservoirs of the dams, while the other two, known as the reference stations, are outside the area of influence of the former dams (one downstream and the other upstream). At these stations, aquatic biocenoses (including benthic macroinvertebrates, biofilms, macrophytes, etc.) are monitored. Since September 2014, the stations are ideally sampled every month from April to October (7 annual surveys) using artificial substrates (glass slides placed in the water). In addition to the diatom survey (floristic list, IBD calculation), the chlorophyll-a concentration is measured. During each campaign, an INRAe experimental sampling protocol is implemented. This protocol involves the immersion (1 month) of glass slides, an in situ measurement of the chlorophyll-a concentration via BentoTorch and then the collection of the biofilm on these glass slides. The biofilm is conditioned in (1) 99.9% ethanol to determine IBDs and floristic lists (outsourced service, based on standard NF T90-354) and (2) mineral water to measure chlorophyll-a concentration using a spectrometer. NB: the year 2023 is not covered in terms of measuring chlorophyll-a concentration via spectrometry due to a problem with the low-temperature storage of samples. This dataset provides measurements of the average daily concentration of chlorophyll-a and pheopigment in µg/cm2/day.

Ce projet a pour objectif de comprendre les échanges entre la nappe souterraine et l’eau de la Sélune. Cette connaissance permettra de prévenir les changements physiques, chimiques et biologiques que la remise en continuité va engendrer sur la qualité de l’eau de la Sélune. Données : - chroniques de hauteurs d'eau - chroniques de mesure de T° à différentes positions dans les sédiments dans la rivière et dans les piézomètres - données de capteurs de pression différentiel à certains endroits de la rivière, - données de concentration d'éléments chimiques (N, P, gaz dissous, ..) dans les sédiments - données de fibre optique - données de campagnes Lidar Sites : Au début du projet, deux sites principaux, de quelques centaines de mètres, sont situés à proximité : - du Pont de Signy - du Pont des Biards D'autres sites pourraient ensuite être ajoutés, si les contraintes logistiques (mobilité de certains protocoles de mesure) le permettent.