Effects of intermittent stream flow on macroinvertebrate community composition and biological traits in a naturally saline Mediterranean stream M.R. Vidal-Abarca * , M.M. Sánchez-Montoya 1 , C. Guerrero 1 , R. Gómez 2 , M.I. Arce 1 , V. García-García 1 , M.L. Suárez 3 Department of Ecology and Hydrology, Regional Campus of International Excellence “Campus Mare Nostrum”, University of Murcia, Campus of Espinardo, 30100 Murcia, Spain article info Article history: Received 26 March 2013 Received in revised form 25 September 2013 Accepted 30 September 2013 Available online Keywords: Benthic invertebrate assemblages Flow intermittence Saline stream Salinity Traits abstract As saline streams are geographically widespread in arid and semiarid regions, flow intermittence frequently occurs as another stressor factor apart from salinity. Rambla Salada is a temporary naturally saline stream with an intermittent reach upstream. This stream is an ideal scenario to study the effects of intermittent stream flow on macroinvertebrate community composition and biological traits in a naturally saline Mediterranean stream. This study analysed three sites with different hydrological re- gimes (one intermittent and two perennials). Flow intermittence exerted low pressure on the macro- invertebrate composition and biological traits which led to the loss of drought-intolerant species and taxa rather than acting as a selective force to promote desiccation-resistant taxa. Macroinvertebrate community at the intermittent site was a subset of the community found in perennial sites, and the presence of flier taxa at this site helped avoid flow cessation. These minor changes have consequences to assess the ecological quality of these saline temporary streams in the context of the Water Framework Directive, given the major differences revealed by some indices between the intermittent and perennial sites as the former obtained lower values due to the presence of few desiccation-intolerant species, which significantly increased the value of those biological indices. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Although saline streams are rare ecosystems in Europe, they are relatively frequent in arid and semiarid regions in general (Williams, 1996, 2002). The naturally water salinity of such streams is due to their drainage catchment lithology (e.g., presence of gypsum and halite-rich evaporite rocks; Gómez et al., 2005) and the balance between rainfall and evapotranspiration (high evapo- transpiration and scarce precipitation) (e.g., Haron and Dragovich, 2010; Williams, 1987). Salinity and osmotic stress potentially acts as a severe abiotic stressor on biota in general, and on macroinvertebrate commu- nities in particular (e.g., Moreno et al., 2010; Piscart et al., 2006). The existing bibliography generally shows that the effects of increasing salinity on freshwater ecosystems leads to reduction in biodiversity (e.g., Williams, et al., 1990; Gallardo-Mayenco, 1994), thus modifying the trophic structure of aquatic communities (Muñoz and Prat, 1994). A recent review by Millán et al. (2011) on saline streams in southeast Spain highlights that while semiarid saline streams share some characteristics with Mediterranean freshwater streams, many other structural and functional aspects differ, fundamentally species composition in macroinvertebrate communities due to the strong selective pressure exerted by salinity. In this sense, Heteroptera, Coleoptera and Diptera are the most diverse groups inhabiting saline streams and on the contrary Ephemeroptera, Trichoptera, Odonata, Crustaceans, Hydrachnidia and Mollusca taxa are scarce (Mellado-Díaz et al., 2008; Millán et al., 2011). In this regard, it is important to consider that salinity trigger values, which act as a selective stressor for aquatic species, seem to * Corresponding author. Tel.: þ34 868 887849; fax: þ34 868 883963. E-mail addresses: charyvag@um.es (M.R. Vidal-Abarca), marsanch@um.es (M.M. Sánchez-Montoya), crisguer@um.es (C. Guerrero), rgomez@um.es (R. Gómez), marisarce@um.es (M.I. Arce), viquigar@um.es (V. García-García), mlsuarez@um.es (M.L. Suárez). 1 Tel.: þ34 868 884653; fax: þ34 868 883963. 2 Tel.: þ34 868 884987; fax: þ34 868 883963. 3 Tel.: þ34 868 884979; fax: þ34 868 883963. Contents lists available at ScienceDirect Journal of Arid Environments journal homepage: www.elsevier.com/locate/jaridenv 0140-1963/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jaridenv.2013.09.008 Journal of Arid Environments 99 (2013) 28e40