Hydroecological implication of long-term flow variations in the middle Paraná river floodplain

[Display omitted] •Droughts and the amplitude of water-level fluctuations have reduced since 1972;•Thus, surface water connectivity has increased in the Middle Paraná River floodplain;•This led to a lentification trend that may have altered ecological diversity patterns. The Paraná River is ranked among the top-ten major rivers of the world. During the last century, the expansion of agriculture and the construction of large dams strongly modified the upper basin but the middle and lower sections are still among the few free-flowing river reaches of this magnitude in the world. However, the great anthropic pressure in the upper basin coupled with the climate variability of the past fifty years affected the hydrology of the lower reaches. In this study, we analyzed the hydrological characteristics of the flow regime from 1905 to 2019. Based on 10 m-resolution satellite images, we performed a cartography of the surface waters covering 15% of the Middle Paraná River floodplain and we analyzed the processes of connectivity for each 50 cm of the river height. We related the hydrological changes with the landscape analyses and discussed their potential implication on the ecosystem functioning. In other words, we highlighted how a regional disturbance in a large river basin affects some hydro-geomorphological processes several hundreds of kilometers downstream, which potentially involves long-term alterations of the structural and functional components of the biota.