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Intro -- Title page -- Table of Contents -- Copyright -- Contributors -- Preface -- Chapter 1: Defining Multiple Stressor Implications -- Abstract -- Acknowledgments -- 1.1 Global Environmental Change: A Source of Stress -- 1.2 Stress, Stressor, Receptor, and Effect: Context and Evolution of the Terms -- 1.3 Types of Stressors According to Their Energy and Frequency -- 1.4 Multiple Stressors in the Literature -- 1.5 Studying the Effects of Multiple Stressors -- 1.6 Ecosystem Responses to Multiple Stressors -- 1.7 Joint Implications of Multiple Stressors for Social and Ecological Systems -- 1.8 Status and Relevance of Multiple Stressors on Water Policies: A Brief Overview -- 1.9 Reading This Book -- Chapter 2: Climate Change and Interactions With Multiple Stressors in Rivers -- Abstract -- Acknowledgments -- 2.1 Introduction -- 2.2 Observations and Predictions of Climate Change in Rivers -- 2.3 Climate Change in Rivers: Similarities to Existing Stressors and Surprises -- 2.4 Vulnerability of River Ecosystems: An Example of Drought as a Manifestation of Climate Change in Addition to Other Stressors -- 2.5 Concluding Remarks -- Chapter 3: Understanding the Nexus Between Hydrological Alteration And Biological Invasions -- Abstract -- Acknowledgments -- 3.1 Altered Flow Regimes and Biological Invasions: Two Facets of Global Change in River Ecosystems -- 3.2 The Alteration-Invasion Nexus -- 3.3 Effects of the Alteration-Invasion Nexus on Riverine Populations and Communities -- 3.4 Effects of the Alteration-Invasion Nexus on Riverine Food Webs -- 3.5 The Alteration-Invasion Nexus as a Freshwater Conservation Challenge -- Chapter 4: Multiple Stressors and Hydromorphological Degradation -- Abstract -- 4.1 Introduction -- 4.2 Interactions Among Hydrological and Morphological Stressors

Las plantaciones de eucalipto (género Eucalyptus) tienen una amplia distribución a escala global y causan preocupación por los efectos que pueden ocasionar sobre el medio ambiente. En este trabajo revisamos la evolución de la superficie cubierta por los eucaliptos en Euskadi y evaluamos sus efectos ambientales a partir de la bibliografía científica existente sobre esta región y sobre la península ibérica. Entre 1986 y 2019, la superficie de plantaciones de eucaliptos se ha cuadruplicado, pasando de 4.866 a 19.643 ha, proceso este que está acelerándose a causa de la plaga de la banda marrón del pino. Los estudios publicados muestran de manera sistemática que las plantaciones de eucaliptos en Euskadi y el resto de la Península tienen un efecto medioambiental negativo si se compara con las plantaciones de pino y, especialmente, con los bosques nativos. Las plantaciones de eucalipto modifican las características del suelo y disminuyen la biodiversidad. Entre los organismos más afectados se encuentran los hongos, líquenes, plantas herbáceas, anfibios, aves e invertebrados acuáticos. También se detectan alteraciones en el funcionamiento del ecosistema, en procesos como la descomposición de hojarasca. Aunque algunas afecciones parecen ser consecuencia de la intensidad con la que se explotan estas plantaciones y podrían reducirse mediante medidas correctoras, otros efectos parecen guardar relación con las características intrínsecas del eucalipto que, en consecuencia, no pueden modificarse.Es previsible que la magnitud de los impactos se agrave conforme se incremente la superficie cubierta por eucaliptales así como el número de rotaciones en sus explotaciones.

River ecosystems are subject to multiple stressors that affect their structure and functioning. Ecosystem structure refers to characteristics such as channel form, water quality or the composition of biological communities, whereas ecosystem functioning refers to processes such as metabolism, organic matter decomposition or secondary production. Structure and functioning respond in contrasting and complementary ways to environmental stressors. Moreover, assessing the response of ecosystem functioning to stressors is critical to understand the effects on the ecosystem services that produce direct benefits to humans. Yet, there is more information on structural than on functional parameters, and despite the many approaches available to measure river ecosystem processes, structural approaches are more widely used, especially in management. One reason for this discrepancy is the lack of synthetic studies analyzing river ecosystem functioning in a way that is useful for both scientists and managers. Here, we present a synthesis of key river ecosystem processes, which provides a description of the main characteristics of each process, including criteria guiding their measurement as well as their respective sensitivity to stressors. We also discuss the current limitations, potential improvements and future steps that the use of functional measures in rivers needs to face. © 2017 The Author(s) ; This work has been supported by the EU 7th Framework Programme Funding under Grant agreement no. 603629-ENV-2013-6.2.1-Globaqua. Additional financial support has been provided by the Basque Government under Grant agreement no. IT951-16. We also acknowledge financial support in terms of pre-doctoral and post-doctoral grants from the University of the Basque Country (O. Pereda, L. Solagaistua, I. Aristi, M. Arroita, A. Martínez) and from the Spanish Ministry of Economy and Competitiveness (S. Monroy). ; Peer reviewed

River regulation has fundamentally altered large sections of the world's river networks. The effects of dams on the structural properties of downstream reaches are well documented, but less is known about their effect on river ecosystem processes. We investigated the effect of dams on river nutrient cycling by comparing net uptake of total dissolved nitrogen (TDN), phosphorus (TDP) and organic carbon (DOC) in river reaches located upstream and downstream from three reservoir systems in the Ebro River basin (NE Iberian Peninsula). Increased hydromorphological stability, organic matter standing stocks and ecosystem metabolism below dams enhanced the whole-reach net uptake of TDN, but not that of TDP or DOC. Upstream from dams, river reaches tended to be at biogeochemical equilibrium (uptake. ≈. release) for all nutrients, whereas river reaches below dams acted as net sinks of TDN. Overall, our results suggest that flow regulation by dams may cause relevant N cycling discontinuities in rivers. Higher net N uptake capacity below dams could lead to reduced N export to downstream ecosystems. Incorporating these discontinuities could significantly improve predictive models of N cycling and transport in complex river networks ; This research was financially supported by the Spanish Ministry of Economy and Competitiveness and FEDER through the project SCARCE (Consolider-Ingenio CSD2009-00065), and by the European Union through the FP7 project GLOBAQUA (Grant agreement No 603629)

River regulation has fundamentally altered large sections of the world's river networks. The effects of dams on the structural properties of downstream reaches are well documented, but less is known about their effect on river ecosystem processes. We investigated the effect of dams on river nutrient cycling by comparing net uptake of total dissolved nitrogen (TDN), phosphorus (TDP) and organic carbon (DOC) in river reaches located upstream and downstream from three reservoir systems in the Ebro River basin (NE Iberian Peninsula). Increased hydromorphological stability, organic matter standing stocks and ecosystem metabolism below dams enhanced the whole-reach net uptake of TDN, but not that of TDP or DOC. Upstream from dams, river reaches tended to be at biogeochemical equilibrium (uptake. ≈. release) for all nutrients, whereas river reaches below dams acted as net sinks of TDN. Overall, our results suggest that flow regulation by dams may cause relevant N cycling discontinuities in rivers. Higher net N uptake capacity below dams could lead to reduced N export to downstream ecosystems. Incorporating these discontinuities could significantly improve predictive models of N cycling and transport in complex river networks ; This research was financially supported by the Spanish Ministry of Economy and Competitiveness and FEDER through the project SCARCE (Consolider-Ingenio CSD2009-00065), and by the European Union through the FP7 project GLOBAQUA (Grant agreement No 603629)

River regulation has fundamentally altered large sections of the world's river networks. The effects of dams on the structural properties of downstream reaches are well documented, but less is known about their effect on river ecosystem processes. We investigated the effect of dams on river nutrient cycling by comparing net uptake of total dissolved nitrogen (TDN), phosphorus (TDP) and organic carbon (DOC) in river reaches located upstream and downstream from three reservoir systems in the Ebro River basin (NE Iberian Peninsula). Increased hydromorphological stability, organic matter standing stocks and ecosystem metabolism below dams enhanced the whole-reach net uptake of TDN, but not that of TDP or DOC. Upstream from dams, river reaches tended to be at biogeochemical equilibrium (uptake. ≈. release) for all nutrients, whereas river reaches below dams acted as net sinks of TDN. Overall, our results suggest that flow regulation by dams may cause relevant N cycling discontinuities in rivers. Higher net N uptake capacity below dams could lead to reduced N export to downstream ecosystems. Incorporating these discontinuities could significantly improve predictive models of N cycling and transport in complex river networks ; This research was financially supported by the Spanish Ministry of Economy and Competitiveness and FEDER through the project SCARCE (Consolider-Ingenio CSD2009-00065), and by the European Union through the FP7 project GLOBAQUA (Grant agreement No 603629)

Human appropriation of water resources may induce water stress in freshwater ecosystems when ecosystem needs are not met. Intensive abstraction and regulation cause river ecosystems to shift towards non-natural flow regimes, which might have implications for their water quality, biological structure and functioning. We performed a meta-analysis of published studies to assess the potential effects of water stress on nutrients, microcontaminants, biological communities (bacteria, algae, invertebrates and fish), and ecosystem functions (organic matter breakdown, gross primary production and respiration). Despite the different nature of the flow regime changes, our meta-analysis showed significant effects of human-driven water stress, such as significant increases in algal biomass and metabolism and reduced invertebrate richness, abundance and density and organic matter decomposition. Water stress also significantly decreased phosphate concentration and increased the concentration of pharmaceutical compounds. The magnitude of significant effects was dependent on climate, rainfall regime, period of the year, river size and type of water stress. Among the different causes of water stress, flow regulation by dams produced the strongest effects, followed by water abstraction and channelization. © 2018, The Author(s). ; This project was funded by the European Commission under the grant No. 603629 – project GLOBAQUA. VF acknowledges financial support from the Portuguese Foundation for Science and Technology (FCT) through UID/MAR/04292/2013 and IF/00129/2014. The authors acknowledge the support from the Economy and Knowledge Department of the Catalan Government through the Consolidated Research Group (ICRA-ENV 2017 SGR 1124). ; Peer reviewed

Many dryland areas are being converted into intensively managed irrigation crops, what can disrupt the hydrological regime, degrade soil and water quality, enhance siltation, erosion and bank instability, and affect biological communities. Still, the impacts of irrigation schemes on the functioning of terrestrial and aquatic ecosystems are poorly understood. Here we assess the effects of irrigation agriculture on breakdown of coarse organic matter in soil and water. We measured breakdown rates of alder and holm oak leaves, and of poplar sticks in terrestrial and aquatic sites following a gradient of increasing irrigation agriculture in a semi-arid Mediterranean basin transformed into irrigation agriculture in 50% of its surface. Spatial patterns of stick breakdown paralleled those of leaf breakdown. In soil, stick breakdown rates were extremely low in non-irrigated sites (0.0001-0.0003day-1), and increased with the intensity of agriculture (0.0018-0.0044day-1). In water, stick breakdown rates ranged from 0.0005 to 0.001day-1, and increased with the area of the basin subject to irrigation agriculture. Results showed that irrigation agriculture affects functioning of both terrestrial and aquatic ecosystems, accelerating decomposition of organic matter, especially in soil. These changes can have important consequences for global carbon budgets. © 2013 Elsevier B.V. ; This work has been supported by the Spanish Ministry of Economy and Competitiveness through the projects CSD2009-00065, CGL2009-13410-C02-01/02 and BFU2010-22053. We also acknowledge financial support in terms of predoctoral grants from the Basque Government (M. Arroita). ; Peer Reviewed

The effluents of wastewater treatment plants (WWTPs) include a complex mixture of nutrients and pollutants. Nutrients can subsidise autotrophic and heterotrophic organisms, while toxic pollutants can act as stressors, depending, for instance, on their concentration and interactions in the environment. Hence, it is difficult to predict the overall effect of WWTP effluents on river ecosystem functioning. We assessed the effects of WWTP effluents on river biofilms and ecosystem metabolism in one river segment upstream from a WWTP and three segments downstream from the WWTP and following a pollution gradient. The photosynthetic capacity and enzymatic activity of biofilms showed no change, with the exception of leucine aminopeptidase, which followed the pollution gradient most likely driven by changes in organic matter availability. The effluent produced mixed effects on ecosystem-scale metabolism. It promoted respiration (subsidy effect), probably as a consequence of enhanced availability of organic matter. On the other hand, and despite enhanced nutrient concentrations, photosynthesis-irradiance relationships showed that the effluent partly decoupled primary production from light availability, thus suggesting a stress effect. Overall, WWTP effluents can alter the balance between autotrophic and heterotrophic processes and produce spatial discontinuities in ecosystem functioning along rivers as a consequence of the mixed contribution of stressors and subsidisers ; This research was supported by the Spanish Ministry of Economy and Competitiveness and FEDER foundings through the SCARCE Consolider-Ingenio CSD2009-00065 and ABSTRACT CGL2012-35848 projects, and the European Communities 7th Framework Programme Funding under Grant agreement no. 603629-ENV-2013-6.2.1-Globaqua. We especially thank the people who assisted in the field and in the laboratory. A thorough review of the manuscript by Prof. Roger I. Jones and two unknown reviewers is deeply appreciated too. We also want to acknowledge financial support in terms of predoctoral grants from the University of the Basque Country (I. Aristi), the Basque Government (M. Arroita), as well as a postdoctoral grant 'Juan de la Cierva' (jci-2010-06397) (D. von Schiller) and a Marie Curie European Reintegration Grant (PERG07-GA-2010-259219) (V. Acuña). This work was partly supported by the Basque Government (Consolidated Research Group: Stream Ecology 7-CA-18/10)

The effluents of wastewater treatment plants (WWTPs) include a complex mixture of nutrients and pollutants. Nutrients can subsidise autotrophic and heterotrophic organisms, while toxic pollutants can act as stressors, depending, for instance, on their concentration and interactions in the environment. Hence, it is difficult to predict the overall effect of WWTP effluents on river ecosystem functioning. We assessed the effects of WWTP effluents on river biofilms and ecosystem metabolism in one river segment upstream from a WWTP and three segments downstream from the WWTP and following a pollution gradient. The photosynthetic capacity and enzymatic activity of biofilms showed no change, with the exception of leucine aminopeptidase, which followed the pollution gradient most likely driven by changes in organic matter availability. The effluent produced mixed effects on ecosystem-scale metabolism. It promoted respiration (subsidy effect), probably as a consequence of enhanced availability of organic matter. On the other hand, and despite enhanced nutrient concentrations, photosynthesis-irradiance relationships showed that the effluent partly decoupled primary production from light availability, thus suggesting a stress effect. Overall, WWTP effluents can alter the balance between autotrophic and heterotrophic processes and produce spatial discontinuities in ecosystem functioning along rivers as a consequence of the mixed contribution of stressors and subsidisers ; This research was supported by the Spanish Ministry of Economy and Competitiveness and FEDER foundings through the SCARCE Consolider-Ingenio CSD2009-00065 and ABSTRACT CGL2012-35848 projects, and the European Communities 7th Framework Programme Funding under Grant agreement no. 603629-ENV-2013-6.2.1-Globaqua. We especially thank the people who assisted in the field and in the laboratory. A thorough review of the manuscript by Prof. Roger I. Jones and two unknown reviewers is deeply appreciated too. We also want to acknowledge financial support in terms of predoctoral grants from the University of the Basque Country (I. Aristi), the Basque Government (M. Arroita), as well as a postdoctoral grant 'Juan de la Cierva' (jci-2010-06397) (D. von Schiller) and a Marie Curie European Reintegration Grant (PERG07-GA-2010-259219) (V. Acuña). This work was partly supported by the Basque Government (Consolidated Research Group: Stream Ecology 7-CA-18/10)