Sandy rivers: an ecological comparison of tropical and temperate zones

WANTZEN, M.K.; BLETTLER, M.C.M; MARCHESE, M.; AMSLER, M.L.; EZCURRA DE DRAGO, I.; DRAGO, E.

Lyon

Conferencia; IS Rivers Conference: Integrative sciences and sustainable development of Rivers.; 2012

Rhone Basin Long Term Environment Research, Rhone-Alps Group of Research on the Infrastructures and Water

The middle and lower (and partly also the upper) segments of the main channel of most large rivers have sandy bed sediments. During several studies on the benthos assemblages and habitat structures of the Paraguay-Paraná river system (Brazil, Paraguay, Argentina) we found interesting patterns between the benthic species assemblages and the physical and chemical habitat characteristics. At one hand these assemblages largely differed between the central strip of the main channel and the banks (including floodplain environments). On the other hand there was a remarkable homogeneity in the benthic assemblages in the longitudinal distribution in the main channel central strip. One example is the occurrence of the assemblage: Narapa bonettoi + Haplotaxis aedeochaeta + Myoretronectes paranaensis on 3500 km river length. A literature survey on temperate rivers and earlier studies on the river Rhine (Germany) confirmed this statement for other rivers. This finding made us develop the hypothesis that the described pattern is common for large rivers world-wide. The sandy mobile bed structure (with dunes and bars) of potamal habitats forces a set of adaptations by the invertebrates which limits but stabilizes the diversity of these important river segments.