Effects of snow cover on the benthic fauna in a glacier‐fed stream

Abstract

1. Alpine streams above the tree line are covered by snow for 6–9 months a year. However, winter dynamics in these streams are poorly known. The annual patterns of macroinvertebrate assemblages were studied in a glacial stream in the Austrian Alps, providing information on conditions under the snow. 2. Snow cover influenced water temperature, the content of benthic organic matter and insect development. Taxa richness and abundance of macroinvertebrates did not show a pronounced seasonal pattern. The duration of the autumn period with stable stream beds was important in determining the abundance and composition of the winter fauna. 3. There were significant differences in species composition between summer and winter. Two potential strategies in larval survival were evident: adaptation to the extreme abiotic conditions in summer (e.g. Diamesa spp.) or avoidance of these conditions and development during winter (e.g. Ephemeroptera and Plecoptera). 4. A comparison of a stream reach with continuous snow cover and a stream reach that remained open throughout winter showed that conditions under snow are suboptimal. At the open stream site, with higher water temperatures and greater food supply (benthic organic matter content), abundance and taxa richness was higher and larval growth was faster. Several taxa were found exclusively at this site. 5. Winter conditions did not provide an entirely homogeneous environment, abiotic conditions changed rapidly, especially at the onset of snowfall and at snowmelt. Continuous monitoring is necessary to recognize spatial and temporal heterogeneity in winter environments and the fauna of alpine streams.

Diversity of macrobenthos in lowland streams: ecological determinants and taxonomic specificity

“…It seems surprising that seasonal variability in taxonomic diversity was noted only in the assemblages of Hirudinea and Gastropoda, whereas seasonal changes in taxonomic composition have been well studied in stream assemblages of larval insects (e.g., Hilsenhoff 1998). Similar incongruence between seasonal changes in diversity and composition of aquatic insects was found by Schütz et al (2001) in a mountain stream.…”

Technical Note: Glacial influence in tropical mountain hydrosystems evidenced by the diurnal cycle in water levels

“…Another important issue is to what extent this method may be applicable in other regions of the world. On the one hand, as diurnal glacial floods always occur during the ablation season in any glacier-fed streams worldwide -e.g., in the tropical Andes (Rabatel et al, 2013), the Himalayas (Sorg et al, 2012), the European Alps (Schutz et al, 2001), the North American Rockies (Lafreneire and Sharp, 2003), and the Arctic (Dahlke et al, 2012) -the core of our approach should be valid. On the other hand, several refinements would be needed to account for the specificities of temperate and arctic regions such as the presence of snow cover outside the glacier or the potential interference of rainfall with diurnal cycles, and strong annual cycle.…”

Nutrient uptake controls and limitation dynamics in north-east Greenland streams

“…This could be the result of variation in quality of organic matter between streams due to varying hydrology, geomorphology and disturbance regimes, and, therefore, variation in bacterial abundance (Findlay et al 2002). All streams had higher organic matter than those included in a study in alpine Austria, where FBOM was typically less than 1% during summer (Schütz et al 2001). These sites in north-east Greenland were comparable to open canopy streams from a study in north-west Wyoming, where FBOM ranged from 3% to 13% ).…”