Life at the Edge: Habitat Condition and Bottom Faunaof Alpine Running Waters



Alpine river systems are fed by glacial icemelt, snowmelt, and groundwater and share common features (e.g., steep gradients, high flow velocities and dynamics) but each source produces a characteristic discharge regime and a distinctive suite of physical and chemical characteristics. The distribution of snow, ice, and groundwater springs varies spatially from stream-reach to catchment scale, resulting in stream segments with characteristics, reflecting the different runoff sources. In recent investigations we have been focusing on the large variety of natural freshwater ecosystems in the Hohe Tauern Nationalpark and, based on hydromorphological conditions at catchment and reach scale, we defined specific river types. Glaciation in the catchment turned out to be a major factor for defining the hydromorphological conditions. Subsequently, we tested the effect of glaciation on the bottom fauna in applying a preliminary set of species traits, indicating strategies and adaptations of resilience and resistance as well as to face environmental harshness. Our results demonstrated the high degree of adaptation of the bottom fauna in alpine streams but especially in glacial streams. As current climate change scenarios propose major impacts at both high altitude and latitudes, considerable changes within the faunal assemblages including species number, densities and the distribution of species traits are to be expected. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)