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).