Influence of hydraulic conditions over dunes on the distribution of the benthic macro-invertebrates in a large sand bed river

M.L. AMSLER; M.C.M. BLETTLER; I. EZCURRA DE DRAGO

WATER RESOURCES RESEARCH

AMER GEOPHYSICAL UNION

Año: 2009 vol. 45 p. 1 - 15

0043-1397

This study aims to relate the flow structure over mobile dunes recorded on the channel bed of the Paraná River (Argentina), with the spatial distribution of the benthic macro-invertebrates. The following main conclusions have been obtained: 1) the dunes found in the active channel could be considered as hydraulic biotopes at a mesohabitat scale: the bed forms in the thalweg region are subjected to higher shear stresses with low benthic densities; 2) differences in benthic densities were also recorded at within-dunes microhabitat scales: the largest densities were found in the dune troughs where small bed shear stresses occur and minimum densities on the low stoss side of dunes where turbulent agitation near the bottom strongly disturb the bed particles; 3) superimposed dunes on larger dunes may be consider as another microhabitat of still smaller dimensions. Summarizing, multiscales approaches are needed if a comprehensive understanding linking hydrodynamics and morphodynamics processes with benthic ecology is intended.