Vertical Distribution of Benthic Macroinvertebrates in Riffles versus Deep Runs with Differing Contents of Fine Sediments (Weidlingbach, Austria)

Abstract

Due to the erosiveness of their sediments, sandstone streams transport high loads of fine particles. The catchment of the Weidlingbach, a 12 km long tributary of the Danube northwest of Vienna, is dominated by calcareous sandstone, marl and slate. Mean sediment grain size ranges from 29.3 to 31.0 mm, and mean pore volume is approximately 20%. The third order study site is divided into a wide, shallow riffle section with high accumulations of fine sediments in the hyporheic zone and a narrow, deep run section with a lower percentage of fine sediments. Invertebrates were sampled to a sediment depth of 60 cm every second month using the freeze-coring-technique with electropositioning.Hyporheic invertebrate densities were significantly higher in sediments of the run than in those of the riffle section. Generally, hyporheic abundances decreased with increasing depth; however, the decline was more distinct within the riffle than the run section. Furthermore, we observed a strong negative correlation between the percentage of fine sediments (<2 mm) and hyporheic invertebrate densities.

Benthic and hyporheic macroinvertebrate distribution within the heads and tails of riffles during baseflow conditions

“…Colmation of hyporheic sediments is widely acknowledged to lead to reductions in the diversity and density of invertebrates within the hyporheic zone (Richards & Bacon, 1994;Strayer et al, 1997;Weigelhofer & Waringer, 2003;Bo et al, 2007). Increasing interstitial fine sediment concentrations have been documented to increase divergence of benthic and hyporheic communities (Descloux et al, 2013); a feature which was evident in this study with 17 taxa being unique to the benthic community.…”

Estimating sample representativeness in a survey of stream caddisfly fauna

“…First, Surber samples deal with the topmost 5 cm of the substrate only. Consequently our species list might increase by applying another sampling technique (Waringer 1987, Weigelhofer & Waringer 2003. Second, although conclusions drawn from this study are based on the examination of caddisflies, this group shows a considerable variability in assemblage structure amongst different aquatic habitats (Dohet 2002), and play a significant role in the dynamics of macroinvertebrate assemblages (Cardinale et al 2001).…”

Destructive effect of quarry effluent on life in a mountain stream

“…The difference was probably yielded because in the mentioned studies the particles were larger (sand) and deposited more rapidly so turbidity is not even reported as a measure of stress. Also, fine sediments cause a more efficient siltation of interstices, especially in riffles which are abundant at our study site, rendering them unsuitable for most indigenous taxa (Bo et al 2007;Weigelhofer & Waringer 2003).…”

“…Sedimentation and siltation is an overwhelming stress for the native invertebrate assemblages (Wood & Armitage 1997;Weigelhofer & Waringer 2003). Primary producer's abundance is lowered and stream metabolism is changed, food quality for macroinvertebrates degrades and interstices are filled, rendering these habitats inadequate for macroinvertebrates (Quinn et al 1992;Parkhill & Gulliver 2002;Bo et al 2007).…”

“…Those unaffected can provide both refugia and a source for recolonization especially for temporary stream fauna (insects that live in streams only during larval development), which represents the majority of species and individuals within these assemblages. Other representatives (here mostly Oligochaeta) are largely burrowing and interstitial species that dwell within the sediment, so we expected that the disturbance would not affect them severely (Weigelhofer & Waringer 2003). All of these facts may alleviate the effect of the disturbance.…”