title: Untangling the effects of multiple human stressors and their impacts on fish assemblages in European running waters.
abstract: This work addresses human stressors and their impacts on fish assemblages at pan-European scale by analysing single and multiple stressors and their interactions. Based on an extensive dataset with 3105 fish sampling sites, patterns of stressors, their combination and nature of interactions, i.e. synergistic, antagonistic and additive were investigated. Geographical distribution and patterns of seven human stressor variables, belonging to four stressor groups (hydrological-, morphological-, water quality- and connectivity stressors), were examined, considering both single and multiple stressor combinations. To quantify the stressors' ecological impact, a set of 22 fish metrics for various fish assemblage types (headwaters, medium gradient rivers, lowland rivers and Mediterranean streams) was analysed by comparing their observed and expected response to different stressors, both acting individually and in combination. Overall, investigated fish sampling sites are affected by 15 different stressor combinations, including 4 stressors acting individually and 11 combinations of two or more stressors; up to 4 stressor groups per fish sampling site occur. Stressor-response analysis shows divergent results among different stressor categories, even though a general trend of decreasing ecological integrity with increasing stressor quantity can be observed. Fish metrics based on density of species 'intolerant to water quality degradation' and 'intolerant to oxygen depletion" responded best to single and multiple stressors and their interactions. Interactions of stressors were additive (40%), synergistic (30%) or antagonistic (30%), emphasizing the importance to consider interactions in multi-stressor analyses. While antagonistic effects are only observed in headwaters and medium-gradient rivers, synergistic effects increase from headwaters over medium gradient rivers and Mediterranean streams to large lowland rivers. The knowledge gained in this work provides a basis for advanced investigations in European river basins and helps prioritizing further restoration and management actions.
authors.affiliation: Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna Max-Emanuelstrasse, 17 1180 Wien, Austria. Electronic address: rafaela.schinegger@boku.ac.at.
authors.forename: Rafaela
authors.initials: R
authors.lastname: Schinegger
authors.affiliation: Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna Max-Emanuelstrasse, 17 1180 Wien, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Palt
authors.affiliation: Forest Research Centre, School of Agriculture, University of Lisbon, Tapada da Ajuda, 1349-017 Lisboa, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Segurado
authors.affiliation: Institute of Hydrobiology and Aquatic Ecosystem Management, University of Natural Resources and Life Sciences, Vienna Max-Emanuelstrasse, 17 1180 Wien, Austria.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schmutz
mesh_terms: D000818:Animals; D057231:Climate Change; D003247:Conservation of Natural Resources / Q000379:methods* / Q000706:statistics & numerical data; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods* / Q000706:statistics & numerical data; D005060:Europe; D005068:Eutrophication; D005399:Fishes / Q000254:growth & development*; D006801:Humans; D062070:Hydrology; D008962:Models, Theoretical; D045483:Rivers / Q000737:chemistry*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D014874:Water Pollutants, Chemical
keywords: Ecological status; Fish metrics; Multiple human stressors; Riverine ecosystems; Water Framework Directive