Artificial flood reduces fine sediment clogging enhancing hyporheic zone physicochemistry and accessibility for macroinvertebrates

Abstract

1. River regulation globally has reduced the riverine connectivity (longitudinal, lateral and vertically) with significant consequences for their abiotic and biotic components. To restore the ecological integrity of regulated rivers, artificial floods are increasingly being employed in large-scale flow restoration efforts. Despite considerable recognition regarding the ecological and geomorphological effects of artificial floods on benthic habitats, understanding the implications for the hyporheic zone is essentially absent. This void in our management knowledge base is considerable given that one of the most widely associated consequences of flow regulation is excessive deposition of fine sediment (sedimentation; particles <2 mm) that often disconnects the hyporheic zone from surface waters.2. In this study, we examined the effects of an artificial flood on the hyporheic zone of the River Spöl in Switzerland. Fine sediment content of shallow benthic substrates (ca. 10 cm) was significantly reduced following the flood. The flushing of fine sediment was also apparent in hyporheic substrates (depths of 0.25 and 0.50 m), resulting in a reconnection of previously clogged interstitial pathways. The opening of interstitial pore space enhanced physicochemical conditions in the hyporheic zone, such as improved dissolved oxygen concentrations, and supported greater taxa richness.3. Alterations in the composition of shallower hyporheic assemblages (0.25 m) were evident following the flood. These results indicated that benthic pore space became more connected to surface waters following the flood, thereby enhancing accessibility for interstitial organisms. 4. Our results suggest that artificial floods can be an effective management tool to restore spatial heterogeneity in sediment composition and pore space and improve vertical connectivity for macroinvertebrates. We anticipate that artificial floods would be required on a regular basis given the re-accumulation of fine sediment 10 months later in our study system. We encourage river managers and scientistsThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Stabilization of fluvial bed sediments by invasive quagga mussels (Dreissena bugensis)

“…The biostabilization of sediments creates stable habitat patches which may act as refugia for invertebrates during high flow events (Cardinale et al, 2004; Lancaster, 2000). However, reduced gravel movement may also result in increased rates of fine sediment clogging, as high flows may be less able to rework surface material and reduce colmation (Mathers et al, 2021; McKenzie et al, 2022). This can alter stream bed processes through many mechanisms (reviewed in Wharton et al, 2017), with potentially deleterious impacts for macrophytes (Jones, Murphy et al, 2012), diatoms (Jones et al, 2014), macroinvertebrates (Jones, Collins et al, 2012), and fish (Kemp et al, 2011).…”

Stream degradation affects aquatic resource subsidies to riparian ground-dwelling spiders

“…60 s to suspend surface fine sediment into the water column before a 50 ml water sample was taken. Samples were routinely processed in the laboratory for mineral content and converted to mass per m 2 using water depths in the stilling well (Mathers et al, 2021b). For each site, the geometric mean of the four samples was taken as the surface fine sediment content measure.…”

Kaolinite Deposition Dynamics and Streambed Clogging During Bedform Migration Under Losing and Gaining Flow Conditions

“…Wharton et al. (2017) refer to colmation as a “pernicious problem” because it can: (a) impede surface‐groundwater fluxes (Nowinski et al., 2011; Partington et al., 2017); (b) affect streambed stability (Dallmann et al., 2021); (c) affect biogeochemical processes (Mathers et al., 2021), and (d) influence various ecological processes (Brunke & Gonser, 1997; Harvey & Gooseff, 2015; Nogaro et al., 2010). Indeed, many cases of sandy streambed clogging have been reported recently (Datry et al., 2015; Korus et al., 2020; Shrivastava et al., 2020).…”

“…For studies on bed mobility, the focus is often on the physical structure of the channel or on the morphology at the interface between the water and the sediments (Ashley, 1990; Leopold, 1994). However, streambed mobilization and re‐deposition can either increase (Cui et al., 2021; Mathers et al., 2021; Wu et al., 2015) or decrease (Dallmann et al., 2021; Teitelbaum et al., 2021) the hydraulic conductivity of the bed, depending on the specific conditions at the sites. Streambeds containing coarse bed material episodically move only during infrequent events.…”