Ecological consequences of consecutive river damming for three groups of bioindicators

• Habitat conditions and spatial position controlled phytobenthos community. Benthic invertebrate community was shaped by habitat conditions. Phytoplankton remained unchanged in spite of dams. Riverine organism best tracked double damming. We studied three commonly used bioindicator groups: phytoplankton, benthic communities’ structure patterns transitions between lotic lentic habitats as consequences two consecutive large dams constructed the early twentieth century on intermediate reach a lowland river Normandy (NW, France), Selune. According to sampling station along river, including reservoir lakes, we defined sorts transitions, from upstream downstream: transition (hereafter len-lot), len-len), within len-lot). Lot-len transition, imposed damming, recovery character afterward dams, promoted different diversity for organisms’ groups. Phytobenthos’ α significantly incresed len-lot highest β score observed lot-len. Both, controls drove structure. mainly Invertebrate’s changed lot-len with being transition. Community’s traits composition invertebrates fitted predictions lotic- lentic- type communities. Phytoplankton’s subsequently scores were low. results, proposed classes organisms based their response damming: i) indifferent or tolerant effect, like phytoplankton communities this study, that neither hampered changes water flow velocity, did not display dispersal limitation neither; ii) sensitive shift but limited capacity dam, study. differed likely due differential capabilities niche breadth; iii) represented while assessment revealed most useful metric disentangle relative contribution modification provoked multiple