The effect of in-stream gravel extraction in a pre-alpine gravel-bed river on hyporheic invertebrate community

Abstract

We investigated the effect of in-stream gravel extraction in a pre-alpine gravel-bed river on hyporheic invertebrate community, together with changes in the hyporheic geomorphology, physicochemistry and biofilm activity. Hyporheic invertebrates were collected, together with environmental data, on seven sampling occasions from June 2004 to May 2005, at two river reaches-at the site of instream gravel extraction and at a site 2.5 km upstream. The hyporheic samples were taken from the river bed and from the gravel bars extending laterally from the stream channel. The invertebrate community was dominated by insect larvae (occasional hyporheos), followed by meiofauna (permanent hyporheos). Stygobionts were present at low species richness and in low densities. Gravel extraction from the stream channel led to changes in the patterns of water exchange between surface and subsurface and changes in the sediment composition at the site. Immediate reductions in density and taxonomic richness of invertebrates were observed, together with changes in their community composition. The hyporheic invertebrate community in the river recovered relatively fast (in 2.5 months) by means of density and taxonomic richness, while by means of community composition invertebrates needed 5-7 months to recover. The impact of fine sediments (\0.1 mm) on biofilm activity measured through ETS activity and hyporheic invertebrate density and taxonomic richness was strongly confirmed in this study.

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

“…Besides these biotic variables, we identified sediment load and electrical conductivity to be related to chironomid assemblage patterns. Conductivity might not be a primal stressor for invertebrates but differs significantly between rhitral and kryal stream sites (Hieber et al, 2003) and is significantly related to invertebrate patterns in recent studies (Mori et al, 2011;Brown et al, 2015). Although we did not quantify disturbance, we derived sediment load as a proxy for hydraulic stress, which integrates discharge and concentration of suspended solids.…”

The response in floodplain respiration of an alpine river to experimental inundation under different temperature regimes

“…This is reflected in substantial spatial variability of respiratory potential measured prior to experimental inundation. In general, respiratory potential of floodplain soils from riparian forest and grasslands was in the range of those previously reported for wetlands (Urbanc‐Berčič and Gaberščik, ), and that from gravel and channel was similar to previous measurements in the same habitats from different rivers (Mori et al ., , ; Simčič and Mori, ). Yet, ETSA was substantially lower in comparison with freshwater lake sediments (de Vicente et al ., ; Germ and Simčič, ; Muri and Simčič, ).…”

Spatial and temporal variability of hyporheic invertebrate community within a stream reach of the River Bača (W Slovenia)

“…Despite low food availability (Simčič & Mori 2007), low mean annual water temperatures and occasional extremely high autumn peaks in discharge (Mori et al 2011), a diverse array of invertebrate taxa was collected from the hyporheic zone in the River Bača, with Cyclopoida juveniles (Copepoda) (46%) and early instars of Leuctra sp. (15%) and Chironomidae (7%) being the most abundant.…”

“…Two decades later, intensive ecological studies of interstitial habitats were performed on four rivers, tributaries of the River Sava, flowing in the south and southeastern part of Ljubljansko Barje (Mori 2004, Dole-Olivier et al 2009. Recently, the ecology of hyporheic biofilm (Simčič & Mori 2007) and the impacts of gravel extraction on the hyporheic invertebrates of the River Bača, a tributary of the River Soča, have been studied (Simčič & Mori 2007, Mori et al 2011.…”