Benthic macro-invertebrates (insects, crustaceans, molluscs, worms) form an important link in the food chain. 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, the aquatic biocenoses (including benthic macroinvertebrates, biofilms, macrophytes, etc.) are monitored. The parameters monitored are the taxonomic composition of the communities at 5 stations in the main river, located upstream, downstream and in the new lotic habitats.

The sampling frequency involves two annual sampling campaigns (spring and autumn). The protocols implemented are the installation of 4 artificial substrates (SUBART) per station and a survey after 1 month of immersion as well as 12 Surber samples per station, in accordance with standard NF T 90-333 (2016), allowing the calculation of the I2M2 in accordance with standard NF T 90-388 (2020) and Mondy et al. 2012, 2012.

This layer shows the location of the study sectors used to monitor benthic macroinvertebrates and the campaigns carried out.

This monitoring was finalised with the latest field acquisitions in 2025.