Invertebrate hydraulic preferences and predicted impacts of changes in discharge in a large river

Abstract

1. Instream habitat models are attractive tools for assessing the impacts of flow restoration on aquatic organisms, but have been rarely used for invertebrates due to the lack of knowledge of their hydraulic preferences. 2. In this study, we provide quantitative models of the hydraulic preferences for 66 invertebrate taxa found in the Upper Rhô ne River (France), and combine these preferences with a statistical habitat model (FSTress) to predict the effects of minimum flow restoration on invertebrate abundances in two bypassed sections of the river. 3. Many taxa show marked preferences for particular hydraulic conditions. Average preferred hydraulic conditions were significantly related to those observed in smaller streams (R 2 = 0.37). 4. Our model predicted that habitat values of 27 taxa should be enhanced by restoration operations, but also predicted a decrease of habitat values in the main channel for 12 limnophilic taxa. However, these taxa are expected to maintain populations by finding refuges in restored cut-off channels and overall invertebrate diversity is predicted to increase in the two bypassed sections studied here.

Potential impact of invasive amphipods on leaf litter recycling in aquatic ecosystems

“…To measure the consequence of the establishment of D. villosus on the potential LBR in the Rhône River, we used data from Mérigoux et al (2009). In these studies, the density of amphipods in the Rhône River was measured at Belley, before the establishment of D. villosus, in Spring and Summer 2002.…”

Flow velocity tolerance of lowland stream caddisfly larvae (Trichoptera)

“…More specifically, within the family of Limnephilidae, the different species occur along a wide range of flow velocities (Mérigoux and Dolédec 2004;Dolédec et al 2007;Sagnes et al 2008;Mérigoux et al 2009). This difference is also reflected by their drift numbers under different flow conditions (Gibbins et al 2005(Gibbins et al , 2010.…”

Alien aquatic macroinvertebrates along the lateral dimension of a large floodplain

“…A more complete habitat spectrum could be sampled and other explanatory variables could be tested to enhance model quality. For instance, Mérigoux et al (2009) showed that D. polymorpha and D. tigrina, have pronounced hydraulic preferences in the main channel of the Rhône River. Limitations in the habitat modelling for alien species could also originate in the presence of cryptic species.…”

“…Nevertheless, this sector is located between two potential sources of colonisation: Lake Geneva upstream and the downstream part of the Rhône River, which is connected to the Rhine via the Saône River. Furthermore, after almost two centuries of embankment and hydro-power construction, the Upper-Rhône floodplain is currently being subjected to a hydrological and ecological restoration programme, which started in 2004 (see Mérigoux et al(2009) for details of this restoration programme). As part of this programme, several floodplain channels were deepened or reconnected to the main channel, and forest harvesting and replanting have occurred.…”