Effects of bottom sediment restoration on interstitial habitat characteristics and benthic macroinvertebrate assemblages in a headwater stream

Abstract

The restoration of in-stream habitats by structural improvement of stream beds is more and more frequent, but the ecological consequences of such works are still little known. We have examined the influence of the deposit of a 15 cm gravel layer over the stream bottom on the chemical characteristics of the interstitial water, the sediment grain size and the composition of the benthic assemblages. We have compared a restored reach to an upstream control over three years and at three seasons each year. Dissolved oxygen, ammonium, nitrite and nitrate contents were measured in both surface and interstitial (À15 cm deep) waters, together with the depth of anoxia estimated using wooden stakes and fine sediment content at the surface. During the same period and seasons, benthic invertebrates were sampled at five points in each reach. The restoration induced an increase in vertical exchanges of water between surface and interstitial habitats, with an increase in the depth of hypoxia. Changes were observed in the composition of invertebrate communities, but not in the density or in the taxonomic richness of assemblages. These changes in assemblages were fragile: a local disturbance (such as a drying period) diminished the beneficial effect of the restoration with the disappearance of several organisms. The viability of such restoration works may be associated with catchment management designed to reduce fine sediment inputs to the river.

The role of benthic microhabitats in determining the effects of hydromorphological river restoration on macroinvertebrates

“…More generally, the impact of landscape-level stressors not mitigated by the restoration measures applied, such as eutrophication, a high organic load, pesticides, siltation, large water temperature fluctuations, and low and high flows, might simply have constrained the effect of local-scale restoration measures (e.g. Sarriquet et al, 2007;Palmer et al, 2010;Feld et al, 2011;Haase et al, 2013). To complicate the habitat-species relationship further, both local and landscape-scale stressors can also affect specific habitat needs of the terrestrial life stages of aquatic insects by impacting the riparian zone.…”

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

“…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. Clogging of the interstitial pore spaces restricts the movement of individuals between benthic and hyporheic sediments (Sarriquet et al, 2007;Descloux et al, 2013;Mathers et al, 2014), with only burrowing taxa or those characterised by a smaller body size able to penetrate deeper into the substratum (Gayraud & Phillipe, 2001;Duan et al, 2009;Xu et al, 2012).…”

From isolation to connectivity: the effect of floodplain lake restoration on sediments as habitats for macroinvertebrate communities

“…The popularity of lake restoration projects is determined by their long-term effectiveness (Gore et al 2001;Clarke et al 2003;Sarriquet et al 2007). The observed decrease in the nitrogen content of lake sediments may be a transitional process caused by intensified nitrification under aerobic conditions (Chapelle 1993).…”