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Assessment of the aquatic macroinvertebrate communities in seven cut-off channels in the French Upper-Rhône River, ten years after the restoration works

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Denomination Maítrise en sciences de l'environnement
Defense Maîtrise : Univ. Genève, 2017
Abstract 1) A functional analysis of aquatic invertebrate assemblages was carried out to supplement a more traditional analysis of taxonomic composition in a restored floodplain of the French Upper-Rhône. The data originated from the long-term (2003-2015) monitoring of seven lateral or cut-off channels in the Belley sector. The restoration of the floodplain occurred in winter 2004-2005 and comprised an increase in the residual flow in the by-passed river and the dredging or reconnection of some floodplain channels. Both measures increased the lateral hydrological connectivity between the river and the floodplain water-bodies. 2) Taxonomic composition and three taxonomic metrics, i.e. rarefied richness, relative abundance of alien species, and Ephemeroptera, Trichoptera and Plecoptera (EPT) richness, were analyzed for up-and downstream sites of six restored and one control cut-off channels. In parallel, 11 traits divided in 59 categories were selected to analyze the trait composition. Three complementary functional diversity indices and seven metrics from Merritt et al. (2002) used as surrogates of ecosystem attributes to provide an insight into functional ecosystem processes. 3) In contrast to our expectations, neither a functional homogenization due to the overall increase of lateral connectivity nor similar patterns of changes in comparable sites were observed. This reflects a high taxonomic and functional diversity between sites. The majority of the biotic variables we assessed at the site scale fluctuated between years, and though dificult to quantify, this suggests a level of dynamism that we interpret as a positive sign in the recovery of a 'living and flowing' Rhône River, as expressed in the original aims of the restoration project. 4) The study points the need to improve our understanding of the cut-off channel functioning to optimize ecological restoration projects of large floodplain sectors. We were also faced with issues related to trait information and we suggest that direct field or laboratory measurements of the traits carried by 'actual' individuals, and linking them with the ecosystem functioning would provide more precise and meaningful functional analyses.
Keywords Aquatic macroinvertebratesFloodplainRestorationFunctional diversityLateral hydrological connectivityDiversityRhône River
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Structures
Research group Ecology and Aquatic Biology
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TIMONER, Pablo. Assessment of the aquatic macroinvertebrate communities in seven cut-off channels in the French Upper-Rhône River, ten years after the restoration works. Université de Genève. Maîtrise, 2017. https://archive-ouverte.unige.ch/unige:96043

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Deposited on : 2017-08-07

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