Does hydrological connectivity control functional characteristics of artificial wetland communities? Evidence from the Rhône River

International audienceThe importance of artificial wetlands for the biodiversity of the Rhône River floodplain was assessed at twelve stations along two sections of the river. The relative roles of the local characteristics of the wetlands (e.g. available nutrients, dissolved oxygen, sediment quality) and of their connectivity with the main channel were considered for three different groups of organisms (benthic micr obes, benthic invertebrates and phytoplankton communities). The functional characteristics of these organisms were determined through their enzymatic activities (for microbes) and biological traits (for invertebrates and phytoplankton). The predicted major role of connections between the wetlands and the river channel was confirmed for environmental characteristics (water and sediment) and benthic invertebrates. Connectivity appeared to be less of a driver of benthic microbial communities and phytoplankton, which were partly or mainly controlled by wetland geometry (water depth, light penetration, and resulting organic matter production). We conclude that connectivity with the river channel needs to be considered jointly with the geometry of wetlands to provide functional solutions when defining management and restoration plans