The Lower Paraguay river-floodplain habitats in the context of the Fluvial Hydrosystem Approach

We report herein the first description of the physical structure of the aquatic habitats of the Lower Paraguay River along 390 km from Asunción city (Paraguay) to the confluence with the Paraná River. The hierarchical ordination of the Fluvial Hydrosystem Approach (FHA) allowed us to classify the Lower Paraguay as a meandering functional sector where five functional sets were identified: (a) main channel, (b) floodplain channel, (c) floodplain lentic water body, (d) tributary, and (f) aquaticterrestrial transition zone. These functional sets encompassed twenty one functional units and fifty eight major mesohabitats. We attribute the riverine habitat diversity to the changes in the channel-floodplain morphology and in the strength, duration and frequency of their hydrological connectivity. The variable river-floodplain-tributary complex developed several types of fluvial-lacustrine boundaries and riverine ecotones.