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

Abstract

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.

Unexpected patterns of chironomid larval size in an extreme environment: a highly glaciated, alpine stream

“…Rivers, from their origin to the mouth, are a continuum with changes in the uppermost reaches affecting the whole ecosystem downstream (e.g., Vannote et al, 1980;Füreder, 2007). High alpine benthic larvae are an important link in stream food webs, as they initially take up and store allochthonous and autochthonous organic material in the stream (Beracko et al, 2016;Niedrist & Füreder, 2017).…”

Chironomid (Insecta: Diptera) assemblages along an Andean altitudinal gradient

“…In recent years, the headwaters of mountain rivers have been the subject of greater attention on account of their lesser exposure to human activities compared with downstream sections (Maiolini & Lencioni 2001). In addition, the benthic communities recorded at high altitudes are more sensitive to environmental changes within their immediate environment (Füreder 2007). For these reasons, the macroinvertebrate communities of these ecosystems are especially good indicators of systematic climate change in the form of global warming (Burgmer et al 2007, Kohler & Maselli 2009).…”

“…Mountain streams can also exhibit distinctive environmental characteristics and flow regimes that relate to their runoff source (e.g. glacial melt, snowmelt or spring thaws; Füreder 1999, 2007, Lods-Crozet et al 2001, Maiolini & Lencioni 2001, Milner et al 2001. Hence highaltitude mountain streams are model systems for the study of longitudinal and seasonal patterns in benthic communities (Finn & Poff 2005).…”

Towards a definition of environmental niches in alpine streams by employing chironomid species preferences

“…Each source of stream generates characteristic conditions regarding physical (water temperature, discharge, substrate dynamics and suspended sediment load) and chemical water quality (Tockner et al, 1997;Füreder, 2007), which are also responsible for the variety of environmental conditions further downstream (Brown et al, 2006a). This diverse abiotic character results in wide ecological gradients, suitable for a variety of benthic invertebrate species to coexist in alpine streams (Hutchinson, 1957;Levine & Hille Ris Lambers, 2009;Blonder et al, 2014).…”