Aquatic and terrestrial biodiversity

Main questions

• What impact will dam removal have on life in the river and on the banks?
• How will plant and animal, aquatic and terrestrial life be reorganised?

Scientific objectives

The aim here is to understand the biological processes involved in restoring ecosystems following the removal of dams.

Monitoring animal recolonisation

The return of migratory species to the Selune (salmon Salmo salar, sea lamprey Petromyzon marinus, river lamprey Lampetra fluviatilis, shad Alosa sp. and eel Anguilla anguilla) is particularly eagerly awaited. The spreading risk of invasive species (including the signal crayfish Pacifastacus leniusculus and the wels catfish Silurus glanis) also represents a considerable challenge. A number of monitoring tools have been put in place: electrofishing, trapping, tissue sampling, isotope analysis, environmental DNA, acoustic cameras and radio-tracking.

Vegetation and bio-indicator species

Our teams also monitor vegetation on riverbanks (riparian vegetation) and bio-indicator species that indicate the quality status of an environment. In particular, this involves monitoring changes in photosynthetic organisms (phytoplankton, biofilm and macrophytes), aquatic macro-invertebrates and benthic-demersal communities in the small bay of Mont Saint Michel (mouth of the Selune river).

Community (re)organisation

Finally, the relationships between the various living compartments, from microorganisms to fish, are being studied. The aim is to identify the complex mechanisms underlying the reorganisation of aquatic and riparian communities after dam removal.