water Article Disentangling the Effects of Multiple Stressors on Large Rivers Using Benthic Invertebrates—A Study of Southeastern European Large Rivers with Implications for Management Gorazd Urbaniˇc 1,* , Zlatko Mihaljevi´c 2 , Vesna Petkovska 3 and Maja Pavlin Urbaniˇc 1 1 URBANZERO Institute for holistic environmental management, Ltd., Selo pri Mirni 17, 8233 Mirna, Slovenia;
[email protected] 2 Faculty of Science, Department of Biology, University of Zagreb, Rooseveltov trg 6, 10000 Zagreb, Croatia;
[email protected] 3 Clinical Institute for Occupational, Traffic and Sports Medicine, University Medical Centre Ljubljana, Poljanski nasip 58, 1000 Ljubljana, Slovenia;
[email protected] * Correspondence:
[email protected]; Tel.: +386-41-509-933 Received: 6 January 2020; Accepted: 22 February 2020; Published: 25 February 2020 Abstract: Predicting anthropogenic actions resulting in undesirable changes in aquatic systems is crucial for the development of effective and sustainable water management strategies. Due to the co-occurrence of stressors and a lack of appropriate data, the effects on large rivers are difficult to elucidate. To overcome this problem, we developed a partial canonical correspondence analyses (pCCA) model using 292 benthic invertebrate taxa from 104 sites that incorporated the effects of three stressors groups: hydromorphology, land use, and water quality. The data covered an environmental gradient from near-natural to heavily altered sites in five large rivers in Southeastern Europe. Prior to developing the multi-stressor model, we assessed the importance of natural characteristics on individual stressor groups. Stressors proved to be the dominant factors in shaping benthic invertebrate assemblages. The pCCA among stressor-groups showed that unique effects dominated over joint effects.