Hydraulic conditions over bed forms control the benthic fauna distribution in a lowland river (Spree River, Germany).

BLETTLER MARTIN; SUKHODOLOV ALEXANDER; TOCKNER KLEMENT

Braunschweig, Alemania

Conferencia; International Conference on Fluvial Hydraulics. River Flow 2010.; 2010

Fluvial Hydraulics Committee of the International Association for Hydro-Environment Engineering and Research (IAHR)

We report preliminary results of a detailed hydraulic-ecological study to identify the effects of flow hydrodynamics and morphodynamic processes on the distribution and composition of benthic invertebrates in a lowland river. We examined a riffle-pool-transitional sequence in a meander bend of the Spree River (Germany) and focused on the detailed flow structures over a representative micro-form in a riffle bed-form. Two invertebrate groups dominated the community: Diptera (mainly Chironomini) and amphipods (Dikerogammarus haemobaphes and Chorophium curvispinum). The results suggest that at the meso-habitat scale (i.e. riffle, pool and transitional zone) hydraulic conditions are most intense in the riffle zone, leading to low densities of invertebrates. At the micro-habitat scale (i.e. within the bed-form), the benthic invertebrates peaked in density on the crest where the bed shear stress was a bit lower comparing with the lee-side (mean differences around 33%). This study suggests that benthic macroinvertebrates prefer the benefits from lower hydrodynamic stress and of more stable environmental conditions in the studied meander, providing refuge and probably food.