Outils de diagnose structurelle et fonctionnelle pour la bioévaluation de la qualité des sédiments associés à la présence de barrages. Approche intégrée de la population au processus écosystémique

Abstract : Sediment evaluation and monitoring is an essential part of ecosystem monitoring since sediments represent an important component of aquatic habitats and are also a potential source of contamination. Current methodologies of their ecotoxic risk assessment do not encompass ecosystemic responses and do not take into account multiple abiotic and biotic stressors. Run-of-river reservoirs entrap a large amount of sediments and constitute an opportunity to develop original risk assessment methodologies that integrate biological responses in situ and their potential effects for river ecosystem functioning. Six run-of-river reservoirs were selected to study the effects of sediment contamination at several spatial and biological scales, thanks to structural and functional approaches. Our results evidenced a selection in faunistic assemblages in response to contamination, associated with low taxonomic and functional diversity. Our results also evidenced sublethal responses, with niches shifts of invertebrate population and modification of biotic interactions. Sediment contamination has also impacted metabolic functional diversity of bacterial communities and fungal richness and biomass. These biocenotic alterations have resulted in disturbances in ecosystemic processes such as leaf breakdown and benthic flux at the water-sediment interface. Ecosystems downstream dams were also impacted, through resuspension of contaminated sediments, alteration of water quality and cascading effects related to structural and functional responses of reservoirs communities. Our findings evidenced challenges of the sediment quality preservation and the need to develop risk assessment methodologies based on the vulnerability at each biological scale in order to understand and elucidate ecological status and trajectories of aquatic ecosystems
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Fanny Colas. Outils de diagnose structurelle et fonctionnelle pour la bioévaluation de la qualité des sédiments associés à la présence de barrages. Approche intégrée de la population au processus écosystémique. Autre. Université de Lorraine, 2012. Français. ⟨NNT : 2012LORR0386⟩. ⟨tel-01749594⟩

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