Ecological Indicators 61 (2016) 234–247 Contents lists available at ScienceDirect Ecological Indicators jo ur nal ho me page: www.elsevier.com/locate/ ecolind Odonates as indicators of the ecological integrity of the river corridor: Development and application of the Odonate River Index (ORI) in northern Italy Bruno Golfieri a,∗ , Sönke Hardersen b , Bruno Maiolini c , Nicola Surian a a Department of Geosciences, University of Padova, Via Gradenigo 6, 35131 Padova, Italy b Corpo Forestale dello Stato, Centro Nazionale per lo Studio e la Conservazione della Biodiversità Forestale “Bosco Fontana”, Strada Mantova 29, 46045 Marmirolo (MN), Italy c E Mach Foundation, Research and Innovation Centre, Via E. Mach 1, 38100 San Michele all’Adige (TN), Italy a r t i c l e i n f o Article history: Received 11 February 2015 Received in revised form 11 September 2015 Accepted 12 September 2015 Available online 6 November 2015 Keywords: Dragonflies Damselflies Bioindicator River assessment Hydromorphological alteration Water Framework Directive a b s t r a c t The assessment of the ecological conditions of rivers is crucial for their appropriate management and restoration. Bioindicators commonly used to evaluate the river status (i.e. diatoms, aquatic macrophytes, benthic macroinvertebrates and fish) detect alterations of water quality, but are not particularly sensitive to hydromorphological degradation, which is another relevant pressure in river systems. Furthermore, those bioindicators are usually applied only to flowing channels. We developed a new multimetric index, the Odonate River Index (ORI), to assess the conditions of the whole corridor in alluvial rivers. The ORI is a development of an evaluation system proposed in Austria, and based on the Odonate Habitat Index (OHI). Odonates were chosen as bioindicators for the ecological integrity of the river corridor, since this taxon provides information on the conditions of their aquatic breeding sites, as well as on the surrounding terrestrial areas, due to its amphibiotic life cycle. We used a case study of 18 reaches from six Italian Alpine rivers, characterized by different morphological conditions and level of human impact. Within each study reach, we selected four sites, both lotic and lentic sites. Dragonfly surveys consisted in field observation of adults, and collection of larvae and exuviae. To define the best sampling strategy, we compared the results of the ORI metrics obtained varying the input data by combining different sampling methods: the best compromise between effort and exhaustiveness was obtained coupling the observation of adults with the collection of exuviae. We found the ORI to be a robust and reliable tool to assess the status of the river corridor in a wide range of environmental conditions and river morphology, being particularly suitable to detect hydromorphological degradation and alterations of the structure of aquatic and riparian vegetation. We identified two limiting factors for the applicability of this index: low water temperatures of the main channel (i.e. mean annual value below 10 ◦ C) and river reaches with no or scarce aquatic and riparian vegetation. In addition to the assessment of river conditions, the ORI could also be applied for monitoring the effects of river restoration actions. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Rivers are heavily affected by human impact and their pristine state is no more recognizable in many temperate regions, due to the long history of anthropogenic influence (Montgomery, 2008; Comiti, 2012). Moreover, rivers are considered the most threatened ecosystems of the world (Abell, 2002). Vörösmarty et al. (2010) list modifications at catchment scale (e.g. land use change and deforestation), water pollution, water abstraction and the diffu- sion of invasive species as the main impacts on river ecosystems. ∗ Corresponding author. Tel.: +39 3495824636; fax: +39 0498279134. E-mail address: bruno.golfieri@unipd.it (B. Golfieri). In addition, the alteration of hydromorphological conditions has been recognized as another fundamental pressure on river ecolog- ical status (Feld, 2004; Lorenz et al., 2004; Tockner et al., 2009). Interventions that modify the hydromorphology of rivers (e.g. channelization, bank protections, dams and sediment mining) have serious consequences for the ecological processes and on the biodi- versity of the river corridor (i.e. the active channel and its adjacent floodplain) (Elosegi et al., 2010; Tockner et al., 2010). The assessment of the ecological conditions of rivers is therefore a crucial issue for their management and restoration. The European Water Framework Directive 2000/60/EC (WFD; European Commission, 2000), the ultimate objective of which is to achieve a good ecological status in European streams within 2015, requires the assessment of biological, physical–chemical and http://dx.doi.org/10.1016/j.ecolind.2015.09.022 1470-160X/© 2015 Elsevier Ltd. All rights reserved.