title: Scale dependency in the hydromorphological control of a stream ecosystem functioning.
abstract: Physical habitat degradation is prevalent in river ecosystems. Although still little is known about the ecological consequences of altered hydromorphology, understanding the factors at play can contribute to sustainable environmental management. In this study we aimed to identify the hydromorphological features controlling a key ecosystem function and the spatial scales where such linkages operate. As hydromorphological and chemical pressures often occur in parallel, we examined the relative importance of hydromorphological and chemical factors as determinants of leaf breakdown. Leaf breakdown assays were investigated at 82 sites of rivers throughout the French territory. Leaf breakdown data were then crossed with data on water quality and with a multi-scale hydromorphological assessment (i.e. upstream catchment, river segment, reach and habitat) when quantitative data were available. Microbial and total leaf breakdown rates exhibited differential responses to both hydromorphological and chemical alterations. Relationships between the chemical quality of the water and leaf breakdown were weak, while hydromorphological integrity explained independently up to 84.2% of leaf breakdown. Hydrological and morphological parameters were the main predictors of microbial leaf breakdown, whereas hydrological parameters had a major effect on total leaf breakdown, particularly at large scales, while morphological parameters were important at smaller scales. Microbial leaf breakdown were best predicted by hydromorphological features defined at the upstream catchment level whereas total leaf breakdown were best predicted by reach and habitat level geomorphic variables. This study demonstrates the use of leaf breakdown in a biomonitoring context and the importance of hydromorphological integrity for the functioning of running water. It provides new insights for environmental decision-makers to identify the management and restoration actions that have to be undertaken including the hydromorphogical features that should be kept in minimal maintenance to support leaf breakdown.
authors.affiliation: Université de Toulouse, CNRS, INP, UPS, EcoLab, 118 Route de Narbonne, 31062 Toulouse, France. Electronic address: fanny.colas@irstea.fr.
authors.forename: Fanny
authors.initials: F
authors.lastname: Colas
authors.affiliation: AFB, Pôle d'Etudes et Recherches AFB-Irstea Hydro-écologie des Plans d'eau, DAST, 94300 Vincennes, France; Irstea, Pôle d'études et recherches AFB-Irstea Hydroécologie des Plans d'eau, Unité de recherche RECOVER, Equipe FRESHCO, 13182 Aix-en-Provence, France. Electronic address: jean-marc.baudoin@onema.fr.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Baudoin
authors.affiliation: Université Paris 1-Pantheon-Sorbonne, CNRS, Laboratoire de Géographie Physique, France. Electronic address: frederic.gob@univ-paris1.fr.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Gob
authors.affiliation: Université Paris 1-Pantheon-Sorbonne, CNRS, Laboratoire de Géographie Physique, France. Electronic address: vincent.tamisier@lgp.cnrs.fr.
authors.forename: Vincent
authors.initials: V
authors.lastname: Tamisier
authors.affiliation: Irstea, Unité de recherche MALY Milieux aquatiques, écologie et pollutions, centre de Lyon-Villeurbanne, 5 rue de la Doua, BP 32108, F-69616 Villeurbanne cedex, France. Electronic address: laurent.valette@irstea.fr.
authors.forename: Laurent
authors.initials: L
authors.lastname: Valette
authors.affiliation: Onema, Direction générale, DCIE, 94300 Vincennes, France. Electronic address: karl.kreutzenberger@onema.fr.
authors.forename: Karl
authors.initials: K
authors.lastname: Kreutzenberger
authors.affiliation: Université de Toulouse, CNRS, INP, UPS, EcoLab, 118 Route de Narbonne, 31062 Toulouse, France. Electronic address: didier.lambrigot@univ-tlse3.fr.
authors.forename: Didier
authors.initials: D
authors.lastname: Lambrigot
authors.affiliation: Université de Toulouse, CNRS, INP, UPS, EcoLab, 118 Route de Narbonne, 31062 Toulouse, France. Electronic address: eric.chauvet@univ-tlse3.fr.
authors.forename: Eric
authors.initials: E
authors.lastname: Chauvet
mesh_terms: D004463:Ecology; D017753:Ecosystem; D004784:Environmental Monitoring; D045483:Rivers; D060753:Water Quality
keywords: Ecosystem functioning; Hydromorphology; Leaf breakdown; Multiple stressors; Scaling effect