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.

Macrophytes are a group of aquatic plants. They are at the base of the food chain and can provide a habitat for many other species. The relative abundance of different species is used to calculate an environmental quality index (IBMR). 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 reference stations, are outside the area of influence of the former dams (one downstream, the other upstream). At these stations, aquatic biocenoses (including benthic macroinvertebrates, biofilms, macrophytes, etc.) are monitored. The parameters monitored are specific composition and cover, at 8 stations in the main course, located upstream, downstream and in neolotic areas of macrophyte communities. The monitoring frequency consists of one annual campaign for stations outside reservoirs (S0, S1 and S5) and two annual campaigns (spring/autumn) for neolotic stations (S2, S3.4, S4.1 and S6). The protocol used is the sampling protocol for macrophytes and bryophytes in accordance with standard NF T90-395 (October 2003), which defines the IBMR. Taxa are sampled for laboratory identification. This layer gives the value of the IBMR and EQR (normalized) index at a station for a campaign, as well as information concerning the robustness of this index, the quantities of taxa used to calculate these indices and also information in terms of the proportion of major floristic groups (heterotrophs, algae, bryophytes, pteridophytes, helophytes, phanerogrames, floating vegetation and submerged vegetation).

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.

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, in situ measurement of chlorophyll-a concentration via BentoTorch and then collection of the biofilm on these glass slides. The biofilm is conditioned in (1) 99.9% ethanol for determination of IBDs and floristic lists (outsourced service, based on standard NF T90-354) and (2) mineral water for measurement of chlorophyll-a concentration using a spectrometer. Taxon identification is based on version v17 of the TAXREF reference. The dataset is currently under embargo.

Macrophytes are a group of aquatic plants. They are at the base of the food chain and can provide a habitat for many other species. The relative abundance of different species is used to calculate an environmental quality index (IBMR). 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 reference stations, are outside the area of influence of the former dams (one downstream, the other upstream). At these stations, aquatic biocenoses (including benthic macroinvertebrates, biofilms, macrophytes, etc.) are monitored. The parameters monitored are specific composition and cover, at 8 stations in the main course, located upstream, downstream and in neolotic areas of macrophyte communities. The monitoring frequency consists of one annual campaign for stations outside reservoirs (S0, S1 and S5) and two annual campaigns (spring/autumn) for neolotic stations (S2, S3.4, S4.1 and S6). The protocol used is the sampling protocol for macrophytes and bryophytes in accordance with standard NF T90-395 (October 2003), which defines the IBMR. Taxa are sampled for laboratory identification. This layer gives Taxon identification is based on version v17 of the TAXREF reference. The dataset is currently under embargo.

The study of riparian vegetation is based on the observation of natural plant communities that spontaneously colonize areas newly exposed following the removal of the Vezins and La-Roche-Qui-Boit dams. The vegetation monitoring program comprises two complementary approaches: i) a vegetation sampling method based on floristic surveys (composition and structure) conducted within a series of plots positioned along a transect ii) monitoring of Vegetation Units (VUs) observed within the valley i) Sampling monitoring: The sampling monitoring system is based on measurements distributed at different points in space (longitudinally and laterally). It aims to identify the diversity of flora and vegetation and describe the structure of emerging formations and plant communities within the neo-valley. Implemented annually (sub-annual only for 2021, before dismantling), this monitoring aims to identify and characterize the evolution trajectories of these vegetation over time. The vegetation sampling protocol is implemented at several stations located along the course of the Sélune and at the mouth of several tributaries located in the right-of-way of the two former reservoirs. The sample of stations is supplemented by a batch of stations positioned outside the right-of-way of the two former reservoirs, downstream and upstream, which constitute so-called "reference" stations. For each station, a transect is established perpendicular to the channel, from the bank to a reference point located at the level of the former water reservoir (i.e. 60m NGF for Vezins & 28.5m NGF for LRQB). Along this transect, 25m2 (5mx5m) quadrats are positioned according to previously set distance intervals. These quadrats (named Q1 to Q1+n) constitute the elementary unit within which abiotic (slope, texture...) and biotic (composition, structure) parameters are characterized and evaluated. The number of quadrats sampled per station varies depending on the width of the exposed bank (or transect length). It is completed by a reference quadrat, located beyond this maximum value (named Q0). The inventory of vascular flora, i.e. herbaceous and woody plant species (excluding bryophytes) within quadrats aims at exhaustiveness and identification up to specific or even sub-specific rank. ii) Monitoring of Vegetation Units: The monitoring system for Vegetation Units is based on the identification of vegetation distributed along the transect at each station in the main stream. It aims to obtain a representative view of diversity and the organization of plant formations and communities. This monitoring consists of identifying the discontinuities in terms of composition and structure of the various vegetation types that develop within the neo-valley along the transect that descends to the bank, and to report their influence. (distance in metres from the reference point at the edge of the old dam). These data can be used to establish a pro rata of the different plant formations encountered along the transect. Although this value is thus really valid only at the transect of each station, this information can potentially constitute an approximation of the heterogeneity and distribution of vegetation at the valley scale. This layer gives, for each riparian vegetation monitoring station and each campaign from 2021 to 2026, the following information: – Campaign information (id, code, date, campaign), – Station information (code, name, protocol applied, number of quadrats, code for the associated Sélune reference point and, as a result: location on the catchment area, distance to sea, distance to source and watercourse) – Information on the transect by campaign (number and length, X, Y, LON coordinates, LAT of reference points "NGF" and end point "rive") – Information regarding the Vegetation Units (VU) identified by campaign (number, description: code, start position, end position, EUNIS3 characteristics, 4) – Origin of the data ("Observatoire Sélune," "Hors Observatoire Sélune," "Projet Séripage," or "Projet Restaure") – “Point” geometry (default) corresponding to the transect reference point – Line (alternative) geometry of the associated transect for each campaign.

The study of riparian vegetation is based on the observation of natural plant communities spontaneously colonizing newly exposed areas following the erasure of the Vezins and La-Roche-Qui-Boit dams. The vegetation monitoring system includes two complementary approaches: i) a vegetation sampling method based on floristic surveys (composition & structure) carried out within a series of quadrats positioned along a transect ii) a monitoring of the vegetation units (UV) observed within the valley This dataset specifically concerns the monitoring of the quadrats used in the vegetation sampling method, only for data from the Sélune Observatory (2021-2026) The sampling monitoring system is based on measurements distributed at different points in space (longitudinally and laterally). It aims to identify the diversity of flora and vegetation and describe the structure of emerging formations and plant communities within the neo-valley. Implemented annually (sub-annual only for 2021, before dismantling), this monitoring aims to identify and characterize the evolution trajectories of these vegetation over time. The vegetation sampling protocol is implemented at several stations located along the course of the Sélune and at the mouth of several tributaries located in the right-of-way of the two former reservoirs. The sample of stations is supplemented by a batch of stations positioned outside the right-of-way of the two former reservoirs, downstream and upstream, which constitute so-called "reference" stations. For each station, a transect is established perpendicular to the channel, from the bank to a reference point located at the level of the former water reservoir (i.e. 60m NGF for Vezins & 28.5m NGF for LRQB). Along this transect, 25m2 (5mx5m) quadrats are positioned according to previously set distance intervals. These quadrats (named Q1 to Q1+n) constitute the elementary unit within which abiotic (slope, texture...) and biotic (composition, structure) parameters are characterized and evaluated. The number of quadrats sampled per station varies depending on the width of the exposed bank (or transect length). It is completed by a reference quadrat, located beyond this maximum value (named Q0). The inventory of vascular flora, i.e. herbaceous and woody plant species within the quadrats, aims to be exhaustive and to identify them up to the specific or even sub-specific rank. This layer gives, for each monitoring quadrat of vegetation sampling from 2021 to 2026, the following information: – Quadrat information (id, code, specific number, distance to station reference point) – Campaign information (id, code, date, campaign), – Station information (code, name, protocol applied, number of quadrats, code for the associated Sélune reference point and, as a result: location on the catchment area, distance to sea, distance to source and watercourse) – Information on the transect by campaign (number and length, X, Y, LON coordinates, LAT of reference points "NGF" and end point "rive") – "Point" geometry corresponding to the reference point of the transect or station

The study of riparian vegetation is based on the observation of natural plant communities spontaneously colonizing newly exposed areas following the erasure of the Vezins and La-Roche-Qui-Boit dams. The vegetation monitoring system includes two complementary approaches: i) a vegetation sampling method based on floristic surveys (composition & structure) carried out within a series of quadrats positioned along a transect ii) a monitoring of the vegetation units (UV) observed within the valley This dataset specifically concerns the overall characterization observed on each quadrat in terms of strata and concerns only the Sélune Observatory (2021-2026). The sampling monitoring system is based on measurements distributed at different points in space (longitudinally and laterally). It aims to identify the diversity of flora and vegetation and describe the structure of emerging formations and plant communities within the neo-valley. Implemented annually (sub-annual only for 2021, before dismantling), this monitoring aims to identify and characterize the evolution trajectories of these vegetation over time. The vegetation sampling protocol is implemented at several stations located along the course of the Sélune and at the mouth of several tributaries located in the right-of-way of the two former reservoirs. The sample of stations is supplemented by a batch of stations positioned outside the right-of-way of the two former reservoirs, downstream and upstream, which constitute so-called "reference" stations. For each station, a transect is established perpendicular to the channel, from the bank to a reference point located at the level of the former water reservoir (i.e. 60m NGF for Vezins & 28.5m NGF for LRQB). Along this transect, 25m2 (5mx5m) quadrats are positioned according to previously set distance intervals. These quadrats (named Q1 to Q1+n) constitute the elementary unit within which abiotic (slope, texture...) and biotic (composition, structure) parameters are characterized and evaluated. The number of quadrats sampled per station varies depending on the width of the exposed bank (or transect length). It is completed by a reference quadrat, located beyond this maximum value (named Q0). The inventory of vascular flora, i.e. herbaceous and woody plant species within the quadrats, aims to be exhaustive and to identify them up to the specific or even sub-specific rank. The characterization of cover by plant species on a quadrat allows to present, for each quadrat, all the species identified in the field (taxonomic determination and proportion (%) of cover on the quadrat and for the stratum considered). This layer gives, for each quadrat of each riparian vegetation monitoring station and each campaign of the Sélune Observatory from 2021 to 2026, the following information: – Quadrat information (id, code, number and distance from its centroid to the station reference point), – Campaign information (id, code, date, campaign), – Station information (code, name, protocol applied, number of quadrats, code for the associated Sélune reference point and, as a result, positioning on the catchment area, distance to sea, distance to source and watercourse, watercourse reference altitude) – Information on the transect by campaign (number and length, X, Y, LON, LAT coordinates of the reference points “NGF” and end point “bank”) – Information concerning the identified taxa: taxonomic determination, scientific name, and vernacular, identification stratum and overlap on this stratum – Information regarding the identification stratum: its wording "muscinal", "herbaceous", "young plant shrub", "low shrub", "high shrub" and "arborescent" as well as the height markers – “Point” geometry (default) corresponding to the transect reference point

As part of the Biomonitoring project and 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. 2 sampling campaigns (spring and autumn) for benthic macroinvertebrates (bmi) have been carried out since September 2014. During each campaign, 2 sampling protocols are implemented: - in accordance with standard NF T90-333, which enables the calculation of the IBG-DCE and I2M2 (‘SURBER’) - via artificial substrates immersed for 1 month (‘SUBART’), in order to focus on measuring the ‘effect of dams’. The protocol is described in: Piscart C., Moreteau, J.C., Beisel J.N. (2006). Monitoring changes in freshwater macroinvertebrate communities along a salinity gradient using artificial substrates. Environmental Monitoring and Assessment 116: 529-542. This layer details the benthic macroinvertebrate taxa and their abundance obtained after analysis (according to standard NF T90-388). These data are distributed by campaign and by sector. Taxa presenting all the morphological criteria clearly visible and characteristic allowing the exactitude of their determination and an irreproachable state of conservation are integrated into the reference collection of the Sélune Observatory. This collection can be consulted on request (see contact point). Taxon determination is based on version v17 of the TAXREF reference. The dataset is currently under embargo.