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Altres ajuts: acords transformatius de la UAB Instituto Nacional de Investigación y Tecnologı́a Agraria y Alimentaria PID2020-114060RR-C33-INFLUOMA Avian influenza viruses (AIVs) can affect wildlife, poultry, and humans, so a One Health perspective is needed to optimize mitigation strategies. Migratory waterfowl globally spread AIVs over long distances. Therefore, the study of AIV persistence in waterfowl staging and breeding areas is key to understanding their transmission dynamics and optimizing management strategies. Here, we used artificial streams mimicking natural conditions of waterfowl habitats in the Mediterranean climate (day/night cycles of photosynthetic active radiation and temperature, low water velocity, and similar microbiome to lowland rivers and stagnant water bodies) and then manipulated temperature and sediment presence (i.e., 10-13 °C vs. 16-18 °C, and presence vs. absence of sediments). An H1N1 low pathogenic AIV (LPAIV) strain was spiked in the streams, and water and sediment samples were collected at different time points until 14 days post-spike to quantify viral RNA and detect infectious particles. Viral RNA was detected until the end of the experiment in both water and sediment samples. In water samples, we observed a significant combined effect of temperature and sediments in viral decay, with higher viral genome loads in colder streams without sediments. In sediment samples, we didn't observe any significant effect of temperature. In contrast to prior laboratory-controlled studies that detect longer persistence times, infectious H1N1 LPAIV was isolated in water samples till 2 days post-spike, and none beyond. Infectious H1N1 LPAIV wasn't isolated from any sediment sample. Our results suggest that slow flowing freshwater surface waters may provide conditions facilitating bird-to-bird transmission for a short period when water temperature are between 10 and 18 °C, though persistence for extended periods (e.g., weeks or months) may be less likely. We hypothesize that experiments simulating real environments, like the one described here, provide a more realistic approach for assessing environmental persistence of AIVs.

In some regions, climate change is increasing the variability of rainfall and the frequency of extreme events such as drought. Consequently, non‐flow periods have grown in length and frequency, both in temporary and in formerly permanent streams. Water abstraction for human use may further prolong these dry periods. We analysed the resistance and resilience of biofilms from permanent and temporary streams to non‐flow conditions. This was achieved by exposing cobbles (collected from permanent and temporary streams) with intact biofilm to 31 days of non‐flow, followed by 20 days of stream flow in artificial stream channels. Biofilm resistance and resilience were assessed at a structural (algal biomass, pigment composition, and algae and cyanobacteria composition) and functional level (photosynthetic efficiency and community metabolism). Algal taxa in biofilms from permanent and temporary streams differed throughout the experiment. Biofilms from permanent streams were less resistant to non‐flow than those from temporary streams at structural level. Permanent stream biofilms also presented lower resilience at a structural level, but responded similarly to temporary stream biofilms at a functional level. Our investigation shows how the non‐flow period disturbed permanent stream biofilms, and suggests that temporary stream biofilms will have greater adaptive capacity as hydroperiod becomes shorter due to climate change.

Temporary streams make up the majority of river networks in many regions around the world. Although they are known to have non-flow periods, it is uncertain in what ways the temporal components of the non-flow period affect stream ecosystems. We analyzed how duration and frequency of the non-flow period influence the biofilm metabolism of 33 Mediterranean streams in NE Iberian Peninsula. Selected streams ranged from perennial to ephemeral, and their hydrology was characterized during a period of 150 days before the sampling. Cobbles were collected from the streams, for which the total biofilm biomass (ash-free dry mass and chlorophyll-a) and metabolism (community respiration and gross primary production) were measured. Metabolic differences were observed between both permanent and temporary streams, as well as within temporary streams. Among these, the frequency of the non-flow period did not affect biofilm biomass or metabolism, but the duration did significantly decrease autotrophic biomass and gross primary production. Severity of the non-flow period (solar radiation and maximum streambed temperature) also affected gross primary production negatively. Thus, 80% of the observed gross primary production variability among all temporary streams was explained by the total duration and the severity of the non-flow period. In contrast, community respiration in the streams was not affected by the temporal components of the non-flow period. Our results highlight the effects of different temporal components of the non-flow period on autotrophic and heterotrophic processes, indicating that longer durations of the non-flow period or high severity conditions might decrease gross primary production promoting heterotrophy.

While wastewater treatment plant (WWTP) effluents have become increasingly recognized as a stressor for receiving rivers, their effects on river microbial communities remain elusive. Moreover, global change is increasing the frequency and duration of desiccation events in river networks, and we ignore how desiccation might influence the response of microbial communities to WWTP effluents. In this study, we evaluated the interaction between desiccation events and WWTP effluents under different dilution capacities. Specifically, we used artificial streams in a replicated regressional design, exposing first a section of the streams to a 7-day desiccation period and then the full stream to different levels of a realistic WWTP effluent dilution, from 0% to 100% of WWTP effluent proportion of the total stream flow. The microbial community response was assessed by means of high-throughput sequencing of 16S rRNA gene amplicons and quantitative PCR targeting ecologically-relevant microbial groups. Threshold Indicator Taxa Analysis (TITAN) was used, together with model fitting, to determine community thresholds and potential indicator taxa. Results show significant interactions between WWTP effluents and desiccation, particularly when sediment type is considered. Indicator taxa included members of Proteobacteria, Actinobacteria and Cyanobacteria, with abrupt changes in community structure at WWTP effluent proportion of the total flow above 50%, which is related to nutrient levels ranging 4.6–5.2 mg N − N O 3 − L−1, 0.21–0.32 mg P − P O 4 3 − L−1 and 7.09–9.00 mg DOC L−1. Our work indicates that situations where WWTP effluents account for >50% of the total river flow might risk of dramatic microbial community structure changes and should be avoided.

Effluents from urban wastewater treatment plants (WWTP) consist of complex mixtures of substances that can affect processes in the receiving ecosystems. Some of these substances (toxic contaminants) stress biological activity at all concentrations, while others (e.g., nutrients) subsidize it at low concentrations and stress it above a threshold, causing subsidy-stress responses. Thus, the overall effects of WWTP effluents depend mostly on their composition and the dilution capacity of the receiving water bodies. We assessed the immediate and legacy effects of WWTP effluents in artificial streams, where we measured the uptake of soluble reactive phosphorus (SRP) by the biofilm, biomass accrual, benthic metabolism and organic matter decomposition (OMD). In a first phase (32 d), the channels were subjected to a gradient of effluent contribution, from pure stream water to pure effluent. WWTP effluent affected the ecosystem processes we measured, although we found no clear subsidy-stress patterns except for biofilm biomass accrual. Instead, most of the processes were subsidized, although they showed complex and process-specific patterns. Benthic metabolism and OMD were subsidized without saturation, as they peaked at medium and high levels of pollution, respectively, but they never fell below control levels. SRP uptake was the only process that decreased with increasing effluent concentration. In a second phase of the experiment (23 d), all channels were kept on pure stream water to analyse the legacy effects of the effluent. For most of the processes, there were clear legacy effects, which followed either subsidy, stress, or subsidy-stress patterns. SRP uptake capacity was stressed with increasing pollution legacy, whereas algal accrual and benthic metabolism continued being subsidized. Conversely, biofilm biomass accrual and OMD showed no legacy effects. Overall, the WWTP effluent caused complex and process-specific responses in our experiment, mainly driven by the mixed contribution of subsidizers and stressors. These results help improving our understanding of the effects of urban pollution on stream ecosystem functioning. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved. This research was supported by the European Union 7th Framework Programme (GLOBAQUA; 603629-ENV-2013-6.2.1). Authors also acknowledge the financial support from the University of the Basque Country (pre-doctoral fellowship to O. Pereda), the Basque Government (Consolidated Research Group: Stream Ecology 7-CA-18/10), and the Economy and Knowledge Department of the Catalan Government (Consolidated Research Group: ICRA-ENV 2017 SGR 1124). Authors are also especially grateful to Maria Casellas, Carme Font, Carmen Gutiérrez, Ferran Romero and Laia Sabater-Liesa for their assistance during the laboratory experiments.

The undervaluation of the ecosystem services that temporary waterways provide to human wellbeing is one of the most important threats for the conservation and management of these ecosystems. Recreational services might be particularly undervalued in temporary waterways, as there is some evidence that social perceptions and attitudes towards rivers and streams may depend on their flow permanency. The objective of this study was to determine if the recreational use (here considered as an indicator of social perceptions) of temporary waterways differs from the recreational use of perennial waterways. We analysed the recreational use of temporary and perennial waterways in a Mediterranean basin using geotagged photographs (with temporal and spatial-coordinate metadata) that were uploaded during the period 2003 -2020 on the outdoor recreational website Wikiloc, as well as on Google Earth. The observed recreational activity in each type of waterway was compared with the expected activity, estimated from the proportion of temporary and perennial waterways in the basin, considering the accessibility from both paved and unpaved roads, proximity to populations and flow permanency were significant drivers of recreational activities associated with waterways, thus confirming our two hypotheses of a negative bias towards temporary waterways.This is the first study of our knowledge reporting evidence on the role of flow permanency on the social perception towards waterways. The undervaluation of temporary waterways is one of their major threats, and we must activity design and implement management actions to change this social perception from educational activities at schools to restoration actions.

Environmental policies fall short in protecting freshwater ecosystems, which are heavily threatened by human pressures and their associated stressors. One reason is that stressor effects depend on the context in which they occur and it is difficult to extrapolate patterns to predict the effect of stressors without these being contextualized in a general frame. This study aims at improving existing decision-making frameworks such as the DPSIR approach (Driver-Pressure-State-Impact-Response) or ERA (Environmental Risk Assessment) in the context of stressors. Here, we delve into stressor-impact relationships in freshwater ecosystems and develop a guideline which includes key characteristics such as stressor type, stressor duration, location, the natural levels of environmental variables to which each ecosystem is used to, among others. This guideline is intended to be useful in a wide range of ecosystem conditions and stressors. Incorporating these guidelines may favor the comparability of scientific results and may lead to a substantial advancement in the efficacy of diagnosis and predictive approaches of impacts.

The concept of Nature-Based Solutions (NBS) has emerged to foster sustainable development by transversally addressing social, economic, and environmental urban challenges. However, there is still a considerable lack of agreement on the conceptualization of NBS, especially concerning typologies, nomenclature, and performance assessments in terms of ecosystem services (ES) and urban challenges (UC). Therefore, this article consolidates the knowledge from 4 European projects to set a path for a common understanding of NBS and thus, facilitate their mainstreaming. To do so, firstly, we performed elicitation workshops to develop an integrative list of NBS, based on the identification of overlaps among NBS from different projects. The terminologies were formalized via web-based surveys. Secondly, the NBS were clustered, following a conceptual hierarchical classification. Thirdly, we developed an integrative assessment of NBS performance (ES and UC) based on the qualitative evaluations from each project. Afterwards, we run a PCA and calculated the evenness index to explore patterns among NBS. The main conceptual advancement resides in providing a list of 32 NBS and putting forward two novel NBS categories: NBS units (NBSu) that are stand-alone green technologies or green urban spaces, which can be combined with other solutions (nature-based or not); NBS interventions (NBSi) that refer to the act of intervening in existing ecosystems and in NBSu, by applying techniques to support natural processes. The statistical analysis suggests that NBSu are more versatile than NBSi in terms of UC and ES. Moreover, the results of the integrative assessment of NBS performance suggest a greater agreement concerning the role of NBS in addressing environmental UC, cultural and regulating ES than regarding socio-economic UC and supporting and provision ES. Finally, the ‘green factor’ and the replication of non-intensive practices occurring in nature seem to be key criteria for practitioners to identify a particular solution as an NBS Authors acknowledge the support from the European Union Horizon 2020 research project EdiCitNet (GA776665), the COST Action Circular City (CA 17133), CLEaN-TOUR project (CTM2017-85385-C2-1-R), the Economy and Knowledge Department of the Catalan Government through Consolidated Research Groups ICRA-ENV (2017SGR1124) and ICRAtech (2017SGR1318). ICRA researchers thank funding from CERCA program (Generalitat de Catalunya). Lluís Corominas acknowledge the Ministry of Economy and Competitiveness for the Ramon and Cajal grant and the corresponding I3 consolidation (RYC-2013-14595). Nataša Atanasova acknowledges the project “Closing material flows by wastewater treatment with green technologies” (ID J2-8162), financially supported by the Slovenian Research Agency Open Access funding provided thanks to the CRUE-CSIC agreement with Elsevier

Freshwater ecosystems are exposed to multiple stressors, but their individual and combined effects remain largely unexplored. Here, we investigated the response of stream biofilm bacterial communities to warming, hydrological stress, and pesticide exposure. We used 24 artificial streams on which epilithic (growing on coarse sediments) and epipsammic (growing on fine sediments) stream biofilms were maintained. Bacterial community composition and estimated function of biofilms exposed during 30 days to individual and combined stressors were assessed using 16S rRNA gene metabarcoding. Among the individual effects by stressors, hydrological stress (i.e., a simulated low-flow situation) was the most relevant, since it significantly altered 57% of the most abundant bacterial taxa (n = 28), followed by warming (21%) and pesticide exposure (11%). Regarding the combined effects, 16% of all stressor combinations resulted in significant interactions on bacterial community composition and estimated function. Antagonistic responses prevailed (57 to 89% of all significant interactions), followed by synergisms (11 to 43%), on specific bacterial taxa, indicating that multiple-stressor scenarios could lead to unexpected shifts in the community composition and associated functions of riverine bacterial communities. IMPORTANCE Freshwater ecosystems such as rivers are of crucial importance for human well-being. However, human activities result in many stressors (e.g., toxic chemicals, increased water temperatures, and hydrological alterations) cooccurring in rivers and streams worldwide. Among the many organisms inhabiting rivers and streams, bacteria are ecologically crucial; they are placed at the base of virtually all food webs and they recycle the organic matter needed for bigger organisms. Most of these bacteria are in close contact with river substratum, where they form the biofilms. There is an urgent need to evaluate the effects of these stressors on river biofilms, so we can anticipate future environmental problems. In this study, we experimentally exposed river biofilms to a pesticide mixture, an increase in water temperature and a simulated low-flow condition, in order to evaluate the individual and joint effects of these stressors on the bacterial community composition and estimated function.

In spite of their great ecological, economic and cultural importance, freshwater ecosystems are one of the most degraded ecosystems in the world affected by a wide array of stressors. Around 60% of surface water bodies are failing good ecological status. Several regulations have been developed (e.g. Water Framework Directive (WFD) (2000/60/EC) in Europe) to protect and enhance the status of water resources. Environmental legislation follows a reactive rather than proactive behaviour resulting in end-of-pipe measures. Further, it sets limits for individual stressors while, at least 40% of European waters are subject to multiple stressors. Further, it does not consider physical, chemical and biological characteristics of receiving ecosystems. Similarly, most results from scientific works addressing multi stressors effects cannot be extrapolated to other fluvial ecosystems if not embedded in a conceptual framework which accounts for each site’s characteristics.DPSIR (Driver-Pressure-State-Impact-Response) model is an analytical framework amended by the European Environment Agency (EEA) under the WFD. Although DPSIR framework has been used in a large number of studies there are still some gaps which hurdle its usefulness. DPSIR do not separate the term “stressor” as an explicit term but it instead incorporates stressor variables in the “state” term which often promotes confusion among managers and scientists. Through an extensive literature review and synthesis, here we propose a multi stressor approach based on a DPSSIR framework (Driver-Pressure-State-Stressor-Impact-Response). One considering the State and the Stressor categories in the model.Main points of our work are that State characterization must include both hydrological and chemical characteristics (usually included in previous studies) but also morphological (mostly forgotten although they play a key role in receiving system’s response linked to spatial heterogeneity and ecological habitats –include hyporheic and floodplains-riparian areas-) and biological characteristics. State should account also for seasonal dynamics which modulate the windows of ecological opportunity. To assess the impact, it is necessary to address stressors interaction and cascading effects throughout the food web, since impact varies among receptor organisms. In this assessment it must be taken into account the natural thresholds (range) to which the receiving system is used to (State); the set point of the receiving system before –temporal/spatial- the action of the stressor (State) and the magnitude of the stressor (degree of change – stressor -).With the use of this new conceptual framework, DPSSIR aims to serve as a basis for both stakeholders to establish a new regulatory framework as well as for scientists when designing an experiment to study pressures and impacts in aquatic ecosystems considering the characteristics of the receiving environment, the interaction between stressors (also context-dependent) and the transfer along the food web. Not based merely on setting limits from laboratory studies with a specific organism. It aims to prevent the degradation of aquatic ecosystems and improve the ecological status of aquatic ecosystems.

From the issue entitled "Special Issue: Understanding effects of global change on water quantity and quality in river basins", INTRODUCTION: The Consolider-Ingenio 2010 project SCARCE, with the full title "Assessing and predicting effects on water quantity and quality in Iberian Rivers caused by global change" aims to examine and predict the relevance of global change on water availability, water quality, and ecosystem services in Mediterranean river basins of the Iberian Peninsula, as well as their socio-economic impacts. Starting in December 2009, it brought together a multidisciplinary team of 11 partner Spanish institutions, as well as the active involvement of water authorities, river basin managers, and other relevant agents as stakeholders. METHODS: The study areas are the Llobregat, Ebro, Jucar, and Guadalquivir river basins. These basins have been included in previous studies and projects, the majority of whom considered some of the aspects included in SCARCE but individually. Historical data will be used as a starting point of the project but also to obtain longer time series. The main added value of SCARCE project is the inclusion of scientific disciplines ranging from hydrology, geomorphology, ecology, chemistry, and ecotoxicology, to engineering, modeling, and economy, in an unprecedented effort in the Mediterranean area. The project performs data mining, field, and lab research as well as modeling and upscaling of the findings to apply them to the entire river basin. RESULTS: Scales ranging from the laboratory to river basins are addressed with the potential to help improve river basin management. The project emphasizes, thus, linking basic research and management practices in a single framework. In fact, one of the main objectives of SCARCE is to act as a bridge between the scientific and the management and to transform research results on management keys and tools for improving the River Basin Management Plans. Here, we outline the general structure of the project and the activities conducted within the ten Work Packages of SCARCE., This work has been supported by the Spanish Ministry of Science and Innovation through the project Consolider-Ingenio 2010 CSD2009-00065. Special thanks are due to all partners of the SCARCE consortium and the peer review panel for ensuring quality results and fruitful collaboration within the project.

Amultitude of pharmaceuticals enter surface waters via discharges of wastewater treatment plants (WWTPs), and many raise environmental and health concerns. Chemical fate models predict their concentrations using estimates of mass loading, dilution and in-stream attenuation. However, current comprehension of the attenuation rates remains a limiting factor for predictive models.We assessed in-stream attenuation of 75 pharmaceuticals in 4 river segments, aiming to characterize in-stream attenuation variability among different pharmaceutical compounds, as well as among river segments differing in environmental conditions. Our study revealed that in-streamattenuation was highly variable among pharmaceuticals and river segments and that none of the considered pharmaceutical physicochemical and molecular properties proved to be relevant in determining the mean attenuation rates. Instead, the octanol–water partition coefficient (Kow) influenced the variability of rates among river segments, likely due to its effect on sorption to sediments and suspended particles, and therefore influencing the balance between the different attenuation mechanisms (biotransformation, photolysis, sorption, and volatilization). The magnitude of themeasured attenuation rates urges scientists to consider themas important as dilutionwhen aiming to predict concentrations in freshwater ecosystems This research was supported by aMarie Curie European Reintegration Grant (PERG07-GA-2010-259219) and by a Marie Curie Career Integration Grant (PCIG9-GA-2011-293535) within the 7th European Community Framework Programme, aswell as by the SpanishMinistry of Economy and Competitiveness through the projects SCARCE (Consolider-Ingenio 2010 CSD2009-00065) and ENDERUS (CTM-2009-13018), and the postdoctoral grants “Juan de la Cierva” (jci-2009-05604 and jci-2010- 06397), and by the European Union through the European Regional Development Fund (FEDER). This work was partly supported by the Generalitat de Catalunya (Consolidated Research Group: Water and Soil Quality Unit 2009-SGR-965)

The Authors Investments for upgrading wastewater treatment plants (WWTPs) with tertiary treatment to reduce microcontaminant loads in surface waters at a catchment scale can be daunting. These investments are highly sensitive to the selection of environmental quality standards (EQSs) for the target microcontaminants. Our hypothesis is that there is a balance between EQS selection and investment that needs to be considered in decision-making. We used a customized microcontaminant fate and transport model coupled to an optimization algorithm to validate this hypothesis in the Llobregat river basin and for the pharmaceutical compound diclofenac. The algorithm optimizes the number of WWTPs in this catchment requiring an upgrade to minimize the total amount of diclofenac that exceeds the EQS in every river section and the total cost. We simulated and optimized 40 scenarios representing a combination of 4 potential EQSs (10, 30, 50 and 100 ng L−1), 5 levels of uncertainty bounds in the predictions of river concentrations and 2 hydrological scenarios (average flows, flows annually exceeding 30% of the days; and environmental flows, flows annually exceeding 99% of the days). The results showthat there is a nonlinear relationship between the EQS and the required investment. The investment increases by 100% from an EQS of 100 ng L−1 to 10 ng L−1, significantly increasing (by 60%) from 30 to 10 ng L−1. Thus, establishing an EQS of 30 ng L−1 would balance environmental protection and costs. The selection of the hydrological conditions also plays a key role in the upgrade analysis because the costs for environmental flows are 50% higher than for average flows. Finally, we highlight that the investment in research would allow the reduction of uncertainties, hence allowing more qualified decisions to be made and a reduction in the WWTP upgrade costs (up to 4 €·household−1·year−1) The authors would like to acknowledge the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 642904 (TreatRec ITN- EID). The authors thank Mirabella Mulder for providing details on the cost breakdown for ozonation and sand filtration. The authors also thank Rafael Marcè (ICRA), Carlos Constantino and Peter Daldorph (Atkins) for giving feedback on the article. Lluís Corominas acknowledges funding from the Spanish Ministry of Economy and Competitiveness for the RYC-2013-14595. Additionally, we acknowledge the Economy and Knowledge Department of the Catalan Government (Consolidated Research Group 2014 SGR 291)

Temporary streams are characterized by the alternation of dry and wet hydrological phases, creating both a harsh environment for the biota as well as a high diversity of opportunities for adaptation. These systems are mainly microbial-based during several of these hydrological phases, and those growing on all solid substrata (biofilms) accordingly change their physical structure and community composition. Biofilms experience large decreases in cell densities and biomass, both of bacteria and algae, during dryness. Algal and bacterial communities show remarkable decreases in their diversity, at least locally (at the habitat scale). Biofilms also respond with significant physiological plasticity to each of the hydrological changes. The decreasing humidity of the substrata through the drying process, and the changing quantity and quality of organic matter and nutrients available in the stream during that process, causes unequal responses on the biofilm bacteria and algae. Biofilm algae are affected faster than bacteria by the hydric stress, and as a result the ecosystem respiration resists longer than gross primary production to the increasing duration of flow intermittency. This response implies enhancing ecosystem heterotrophy, a pattern that can be exacerbated in temporary streams suffering of longer dry periods under global change This work has received a grant from the European Community 7th Framework Programme undergrant agreement No. 603629-ENV-2013-6.2.1-Globaqua.The authors acknowledge the support from the Economy and Knowledge Department of the Catalan Government as being part of the Consolidated Research Group of the Catalan Institute for Water Research (2014SGR291)

The current knowledge on bioaccumulation of emerging contaminants (ECs) in aquatic invertebrates exposed to the realistic environmental concentrations is limited. Even less is known about the effects of chemical pollution exposure on the metabolome of aquatic invertebrates. We conducted an in situ translocation experiment with passive filter-feeding caddisfly larvae (Hydropsyche sp.) in an effluent-influenced river in order to i) unravel the bioaccumulation (and recovery) dynamics of ECs in aquatic invertebrates, and ii) test whether exposure to environmentally realistic concentrations of ECs will translate into metabolic profile changes in the insects. The experiment was carried out at two sites, upstream and downstream of the discharge of an urban wastewater treatment plant effluent. The translocated animals were collected at 2-week intervals for 46 days. Both pharmaceuticals and endocrine disrupting compounds (EDCs) were detected in water (62 and 7 compounds, respectively), whereas in Hydropsyche tissues 5 EDCs accumulated. Overall, specimens from the upstream site translocated to the impacted site reached higher ECs concentrations in their tissues, as a reflection of the contaminants’ water concentrations. However, bioaccumulation was a temporary process susceptible to change under lower contaminant concentrations. Non-targeted metabolite profiling detected fine metabolic changes in translocated Hydropsyche larvae. Both translocations equally induced stress, but it was higher in animals translocated to the impacted site.

Intermittent streams (IS) comprise a large proportion of the drainage network in many parts of the world. The non‐flow period of IS are known to impact stream biota because aquatic habitats dry out. However, less well understood are the relative effects of the temporal component of these drying events including their duration and frequency. Here, we characterised effects of temporal component of drying events on abundant and species‐rich meiofauna. The effects were assessed in 22 streams in the north‐eastern Iberian Peninsula. The duration and frequency of non‐flow events was characterized over a period of 250 days prior to sampling the sediment‐dwelling meiofauna in riffle zones that completely dried out. Overall, meiofauna abundances were amongst the highest ever reported for streambeds. Most meiofaunal taxa correlated positively with the frequency of drying events and correlated positively with the length of dry periods recorded shortly before sampling, suggesting that the community was able to recover quickly. Tardigrades were the only group to correlate positively with the longest dry periods, suggesting that they had the best resilience capabilities in streams that had experienced the longest droughts. On average, nematodes made up half of the meiofauna. We identified a total of 113 different nematode species. The nematode community was more taxonomically diverse in IS, with a smaller proportion of bacterivores and a higher proportion of fungivore species such as Filenchus vulgaris. Thereby resembling the trophic structure commonly observed in soil ecosystems. Our results show that most meiofauna were positively influenced by drying disturbance, that is being able to quickly recover after them. This suggests outstanding resilience capabilities, and points out meiofaunal organisms as key players for kick‐starting stream food webs and functions once flow returns This study was supported by the SPACESTREAM project (CGL2017-88640-C2-1-R) from the Spanish Ministry of Economy and Competitiveness and the Consolidated Research Group ICRA-ENV (2017 SGR 1124) from the Economy and Knowledge Department of the Catalan Government

1. River ecosystems worldwide are affected by altered flow regimes, and an advanced science and practice of environmental flows has developed to understand and reduce these impacts. But most environmental flows approaches ignore flow intermittency, which is a natural feature of 30% of the global river network length. Ignoring flow intermittency when setting environmental flows in naturally intermittent rivers might lead to deleterious ecological effects. \ud \ud 2. We review evidence of the ecological effects of flow intermittency and provide guidance to incorporate intermittency (non-flow events) into existing methods judged as suitable for application in temporary waterways. \ud \ud 3. To better integrate non-flow events into hydrological methods, we propose a suite of new indicators to be used in the Range of Variability Approach. These indicators reflect dry periods and the unpredictable nature of temporary waterways. We develop a predictability index for protecting those species adapted to temporary conditions. \ud \ud 4. For hydraulic habitat models, we find that mesohabitat methods are particularly effective for describing complex habitat dynamics during dry phases. We present an example of the European eel to show the relationship between discharge and non-flow days and wet area, habitat suitability, and connectivity. \ud \ud 5. We find that existing holistic approaches may be applied to temporary waterways without significant structural alteration to their stepwise frameworks, but new component methods are needed to address flow-related aspects across both flow and non-flow periods of the flow regime. \ud \ud 6. Synthesis and applications. Setting environmental flow requirements for temporary waterways requires modification and enhancement of existing approaches and methodologies, most notably the explicit consideration of non‐flow events and greater integration of specific geomorphic, hydrogeologic, and hydraulic elements. Temporary waterways are among the freshwater ecosystems most vulnerable to alterations in flow regimes, and they are also under great pressure. The methodological modifications recommended in this paper will aid water managers in protecting key components of temporary flow regimes, thereby preserving their unique ecology and associated services.

Human consumption of pharmaceuticals leads to high concentrations of pharmaceuticals in wastewater, which is usually not or insufficiently collected and treated before release into freshwater ecosystems. There, pharmaceuticals may pose a threat to aquatic biota. Unfortunately, occurrence data of pharmaceuticals in freshwaters at the global scale is scarce and unevenly distributed, thus preventing the identification of hotspots, the prediction of the impact of Global Change (particularly streamflow and population changes) on their occurrence, and the design of appropriate mitigation actions. Here, we use diclofenac (DCL) as a typical pharmaceutical contaminant, and a global model of DCL chemical fate based on wastewater sanitation, population density and hydrology to estimate current concentrations in the river network, the impact of future changes in runoff and population, and potential mitigation actions in line with the Sustainable Development Goals. Our model is calibrated against measurements available in the literature. We estimate that 2.74 ± 0.63% of global river network length has DCL concentrations exceeding the proposed EU Watch list limit (100 ng L-1). Furthermore, many rivers downstream from highly populated areas show values beyond 1000 ng L-1, particularly those associated to megacities in Asia lacking sufficient wastewater treatment. This situation will worsen with Global Change, as streamflow changes and human population growth will increase the proportion of the river network above 100 ng L-1 up to 3.10 ± 0.72%. Given this background, we assessed feasible source and end-of-pipe mitigation actions, including per capita consumption reduction through eco-directed sustainable prescribing (EDSP), the implementation of the United Nations Sustainable Development Goal (SDG) 6 of halving the proportion of population without access to safely managed sanitation services, and improvement of wastewater treatment plants up to the Swiss standards. Among the considered end-of-pipe mitigation actions, implementation of SDG 6 was the most effective, reducing the proportion of the river network above 100 ng L-1 down to 2.95 ± 0.68%. However, EDSP brought this proportion down to 2.80 ± 0.64%. Overall, our findings indicate that the sole implementation of technological improvements will be insufficient to prevent the expected increase in pharmaceuticals concentration, and that technological solution need to be combined with source mitigation actions., Authors acknowledge the support from the Economy and Knowledge Department of the Catalan Government through Consolidated Research Group (ICRA-ENV 2017 SGR 1124), as well as from the CERCA program.

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).

An increasing amount of carbon-based nanomaterials (CNM) (mostly fullerenes, carbon nanotubes and graphene) has been observed in aquatic systems over the last years. However, the potential toxicity of these CNM on aquatic ecosystems remains unclear. This paper reviews the existing literature on the toxic effects of CNM in aquatic organisms as well as the toxic effects of CNM through influencing the toxicity of other micro-pollutants, and outlines a series of research needs to reduce the uncertainty associated with CNMs toxic effects. The results show that environmental concentrations of CNM do not pose a threat on aquatic organisms on their own. The observed concentrations of CNM in aquatic environments are in the order of ngL-1 or even lower, much below than the lowest observed effect concentrations (LOEC) on different aquatic organisms (in the order of mgL-1). Toxic effects have been mainly observed in short-term experiments at high concentrations, and toxicity principally depends on the type of organisms, exposition time and CNM preparation methods. Moreover, we observed that CNM interact (establishing synergistic and/or antagonistic effects) with other micro-pollutants. Apparently, the resulting interaction is highly dependent on the chemical properties of each micro-pollutant, CNM acting either as carriers or as sorbents, thereby modifying the original toxicity of the contaminants. Results stress the need of studying the interactive effects of CNM with other micro-pollutants at environmental relevant concentrations, as well as their effects on biological communities in the long-term.

Global change is dramatically altering flow regimes worldwide. Among the most important consequences are the transition of many permanent waterways to temporary waterways, the increase in duration and frequency of non‐flow periods of temporary streams, and the increase in the severity (i.e. irradiance, temperature and humidity) of the non‐flow period. Nowadays, there is a lack of knowledge on how changes in duration, frequency and severity of the non‐flow period will reflect on biodiversity and biogeochemical changes in temporary streams. We designed a manipulative experiment using artificial streams to evaluate the effects of severity of the non‐flow period on stream biofilms. Sixteen artificial streams were assigned to four treatments: continuous flow, continuous intermittency and intermittency with and without rain events. Effects were assessed on selected features of stream biofilm structure (i.e. bacterial density and basal fluorescence) and function (photosynthetic efficiency and enzymatic activities), as well as CO₂ emissions and dissolved organic matter quantity and quality from water column and sediments. The occurrence of rain events during the non‐flow period enhanced organic carbon processing and CO₂ emissions to the atmosphere, reducing the sediment reservoir of exportable organic carbon and therefore reducing the dissolved organic carbon exports from streambeds at flow resumption. Given the ongoing reducing trends in the frequency of rain events in semi‐arid and arid regions, we expect temporary streams to process and emit less and to export more carbon to downstream systems.

The growing awareness of the relevance of organic microcontaminants on the environment has led to a growing number of studies on attenuation of these compounds in wastewater treatment plants (WWTP) and rivers. However, the effects of the sampling strategies (frequency and duration of composite samples) on the attenuation estimates are largely unknown. Our goal was to assess how frequency and duration of composite samples influence uncertainty of the attenuation estimates in WWTPs and rivers. Furthermore, we also assessed how compound consumption rate and degradability influence uncertainty. The assessment was conducted through simulating the integrated wastewater system of Puigcerda (NE Iberian Peninsula) using a sewer pattern generator and a coupled model of WWTP and river. Results showed that the sampling strategy is especially critical at the influent of WWTP, particularly when the number of toilet flushes containing the compound of interest is small (≤100 toilet flushes with compound day −1 ), and less critical at the effluent of the WWTP and in the river due to the mixing effects of the WWTP. For example, at the WWTP, when evaluating a compound that is present in 50 pulses·d −1 using a sampling frequency of 15-min to collect a 24-h composite sample, the attenuation uncertainty can range from 94% (0% degradability) to 9% (90% degradability). The estimation of attenuation in rivers is less critical than in WWTPs, as the attenuation uncertainty was lower than 10% for all evaluated scenarios. Interestingly, the errors in the estimates of attenuation are usually lower than those of loads for most sampling strategies and compound characteristics (e.g. consumption and degradability), although the opposite occurs for compounds with low consumption and inappropriate sampling strategies at the WWTP. Hence, when designing a sampling campaign, one should consider the influence of compounds' consumption and degradability as well as the desired level of accuracy in attenuation estimations.

Temporary streams and rivers support biodiversity and provide valuable goods and services, especially in arid and semi-arid landscapes. However, temporary streams and rivers are being degraded at alarming rates owing to development, hydromorphological alteration, and disposal of waste water, among other stressors, and pressure will likely increase under global change. Here we propose that it is key to manage temporary streams and rivers as a unique ecohydrological type and not as a permanent waterway or a terrestrial ecosystem. Nevertheless, two challenges hinder this goal. First, data availability on intermittent low regimes and associated biotas is currently scarce. As a consequence, flow-ecology relationships in temporary waterways are largely unknown, and appropriate metrics to define and monitor their ecological status are missing. Second, the ecological and social values of temporary streams and rivers are often underestimated, being regarded as secondary ecosystems relative to permanent waterways. To conserve temporary streams and rivers, ecologists need to define them as unique ecosystems and conservation targets, and practitioners need to systematically collect biological and hydrological data in these ecosystems. Innovative approaches at the intersection of ecology, citizen science, and management, can also contribute to their management and conservation by: i) mapping them, ii) informing people about their ecological values, iii) safeguarding them from further human threats, iv) preserving their flow regime when managing reservoirs, wastewater treatment plants, and water abstraction activities, and v) restoring physically-degraded temporary reaches (e.g. due to gravel mining and off-road use) or reaches that have lost historical flows due to increasing drought severity, diversions, and groundwater overuse.

Small Natural Features (SNFs) are analogous to keystone species in that they have ecological importance that is disproportionate to their size. Thus the recognition and management of SNFs can be an efficient way to conserve biodiversity and ecosystem services. In particular, while the size of SNFs can engender threats (e.g., they are often overlooked and are relatively vulnerable to complete destruction), small size also leads to special conservation opportunities (e.g., integration with resource uses such as forestry or fisheries). Commonly, SNF conservation begins with education and inventory to form a foundation for appropriate, targeted protection and/or sustainable management. However, in cases of severe degradation or loss, more intensive activities such as restoration or creation may be required. Diverse approaches to conservation action are possible. For example, sometimes SNF conservation is undertaken incidentally to other efforts or on a voluntary basis; sometimes it involves substantial economic incentives or restrictive regulations. In general, the required investment for SNF conservation is likely to be smaller than that for larger areas, with disproportionate benefits given the substantial spatio-temporal influence of these features. In practice, conservation of SNFs should be complementary to traditional, larger-scale, forms of conservation by fostering creative, constructive efforts to conserve some seemingly minor features; features that have previously unknown or unappreciated roles critical to their broader ecosystems and to biodiversity.

Diel temperature patterns are changing because of global warming, with higher temperatures being predicted to be more pronounced at night. Biological reactions are temperature dependent, with some occurring only during the daylight hours (e.g., light photosynthesis) and other during the entire day (e.g., respiration). Consequently, we expect the modification of daily temperature cycles to alter microbial biological reactions in stream sediments. Here, we aimed to study the effect of warming and changes of the diel temperature patterns on stream sediment biofilm functions tied to organic carbon decomposition, as well as on biofilm meiofaunal community structure. We performed an eight-week experiment with 12 artificial streams subjected to three different diel temperature patterns: warming, warmer nights and control. Significant effects of warming on biofilm function and structure were mainly detected in the long term. Our results showed that warming altered biofilm function, especially in the warmer nights' treatment, which enhanced β-glucosidase enzyme activity. Interestingly, clear opposite diel patterns were observed for dissolved organic carbon and β-glucosidase activity, suggesting that, at night, sediment bacteria quickly consume the input of photosynthetic dissolved organic carbon labile compounds created during light-time. The biofilm structure was also altered by warming, as both warming and warmer night treatments enhanced copepod abundance and diminished abundances of turbellaria and nematodes, which, in turn, controlled bacterial, algal and ciliate communities. Overall, we conclude that warming has strong effect on sediment biofilm structure and enhanced microbial organic matter degradation which might, consequently, affect higher trophic levels and river carbon cycling.

Global change exposes ecosystems to a myriad of stressors differing in their spatial (i.e. surface of stressed area) and temporal (i.e. exposure time) components. Among freshwater ecosystems, rivers and streams are subject to physical, chemical and biological stressors, which interact with each other and might produce diverging effects depending on exposure time. We conducted a manipulative experiment using 24 artificial streams to examine the individual and combined effects of warming (1.6 °C increase in water temperature), hydrological stress (simulated low-flow situation) and chemical stress caused by pesticide exposure (15.1–156.7 ng L−1) on river biofilms. We examined whether co-occurring stressors could lead to non-additive effects, and if these differed at two different exposure times. Specifically, structural and functional biofilm responses were assessed after 48 hours (short-term effects) and after 30 days (long-term effects) of exposure. Hydrological stress caused strong negative impacts on river biofilms, whereas effects of warming and pesticide exposure were less intense, although increasing on the long term. Most stressor combinations (71%) resulted in non-significant interactions, suggesting overall additive effects, but some non-additive interactions also occurred. Among non-additive interactions, 59% were classified as antagonisms after short-term exposure to the different stressor combinations, rising to 86% at long term. Our results indicate that a 30-day exposure period to multiple stressors increases the frequency of antagonistic interactions compared to a 48-hour exposure to the same conditions. Overall, the impacts of multiple-stressor occurrences appear to be hardly predictable from individual effects, highlighting the need to consider temporal components such as duration when predicting the effects of multiple stressors.

International audience; Urban wastewater effluents bring large amounts of nutrients, organic matter and organic micro- contaminants into freshwater ecosystems. The effects of this complex mixture of pollutants on fresh- water invertebrates have been studied mainly in temperate rivers and streams with high dilution capacities. In contrast, Mediterranean streams and rivers have lower dilution capacities especially during the seasonal drought, and are therefore exposed to high concentrations of pollutants. Here, we assess the effects of urban wastewater pollution on invertebrate communities from Mediterranean streams under different hydrological conditions. Specifically, we assessed the invertebrates taxonomic composition and functional biological traits in 12 streams, differing in stream and substrate size (sand or cobbles), under low (2 surveys) and baseflow (1 survey) conditions. In each stream, we selected reaches both upstream and downstream of the wastewater discharge point. Our results indicate that urban wastewater pollution favours the most tolerant invertebrate taxa and homogenises functional trait composition over time. Changes in functional traits were more evident during the seasonal drought, when the low flow con- ditions at the upstream and downstream sites were more severe and, pollutant concentrations down- stream were at their highest. However, the effects of urban wastewater pollution were not uniform in the downstream sites; as local invertebrate communities differed in according to the river substrate and stream size (i.e., width and discharge). Overall, urban pollution caused by wastewater enhanced both, taxonomic and functional differences between the invertebrate communities. Such an absence of homogenisation among wastewater pollution impacted sites was probably related to the relevant role of stream substrate-size as well flow conditions in the rivers receiving the impact. These are attributes that need to be considered when setting the pollutant discharge limits in rivers and streams receiving effluents.

GLOBAL-FATE is an open-source, multiplatform, and flexible contaminant fate model that links human consumption of pharmaceutical-like compounds with their concentration in the river network at the global scale. GLOBAL-FATE simulates human consumption and excretion of pharmaceuticals, the attenuation of the contaminant load in wastewater treatment plants, and runoff and contaminant routing along the river network under steady-state, including first order decay of the contaminant in rivers reaches, lakes, and reservoirs. We provide a comprehensive description of model equations and the overall structure of the model, with particular attention to input/output datasets. GLOBAL-FATE is written in C and can be compiled in any platform, and uses inputs in standard GIS format. Additionally, the model can be run inside QGIS as a plug-in. The model has no built-in working resolution, which depends on the user inputs. We exemplify the application of GLOBAL-FATE solving the global concentration of diclofenac in the river network. A comparison with a dataset of diclofenac concentration observations in rivers suggest that GLOBAL-FATE can be successfully applied in real case modelling exercises. The model is particularly sensitive to the generation of contaminant loads by human pharmaceutical consumption, and also to the processes governing contaminant attenuation in the river network.

A huge variety of organic microcontaminants are presently detected in freshwater ecosystems, but there is still a lack of knowledge about their interactions, either with living organisms or with other contaminants. Actually, carbon nanomaterials like fullerenes (C60) can act as carriers of organic microcontaminants, but their relevance in processes like bioaccumulation and biotransformation of organic microcontaminants by organisms is unknown. In this study, mesocosm experiments were used to assess the bioaccumulation and biotransformation of three organic microcontaminants (venlafaxine, diuron and triclosan) in river biofilms, and to understand how much the concomitant presence of C60 at environmental relevant concentrations could impact these processes. Results indicated that venlafaxine exhibited the highest bioaccumulation (13% of the initial concentration of venlafaxine in water), while biotransformation was more evident for triclosan (5% of the initial concentration of triclosan in water). Furthermore, biotransformation products such as methyl-triclosan were also present in the biofilm, with levels up to 42% of the concentration of accumulated triclosan. The presence of C60 did not involve relevant changes in the bioaccumulation and biotransformation of microcontaminants in biofilms, which showed similar patterns. Nevertheless, the study shows that a detailed evaluation of the partition of the organic microcontaminants and their transformation products in freshwater systems are important to better understand the impact of the co-existence of others microcontaminants, like carbon nanomaterials, in their possible routes of bioaccumulation and biotransformation. © 2018 Elsevier Inc., This work has been funded by the Spanish Ministry of Economy and Competitiveness (project NANOTRANSFER; ERA SIINN PCIN-2015-182-C02-02 and project PLAS-MED; CTM2017-89701-C3-2-R). Authors also acknowledge the support from the Economy and Knowledge Department of the Catalan Government through Consolidated Research Group (ICRA-ENV 2017 SGR 1124 & 2017 SGR 1404). Lúcia H.M.L.M. Santos acknowledges the Juan de la Cierva Program (FJCI-2014-22377) and Sara Rodríguez-Mozaz acknowledges the Ramon y Cajal Program (RYC-2014-16707). Funding sources This work has been funded by the Spanish Ministry of Economy and Competitiveness (project NANOTRANSFER; ERA SIINN PCIN-2015-182-C02-02 and project PLAS-MED; CTM2017-89701-C3-2-R). Authors also acknowledge the support from the Economy and Knowledge Department of the Catalan Government through Consolidated Research Group (ICRA-ENV 2017 SGR 1124 & 2017 SGR 1404). Lúcia H.M.L.M. Santos acknowledges the Juan de la Cierva program (FJCI-2014-22377) and Sara Rodríguez-Mozaz acknowledges the Ramon y Cajal program (RYC-2014-16707).

Ecosystem services have become a mainstream topic in research and policy agendas, and their relevance in nature management is also rapidly increasing. Ecosystem services are grounded on biodiversity and ecosystem functions, but they are also shaped by socioeconomic factors, such as water or food demand. Because of their linkages with the biophysical domain, any effect of individual or multiple stressors might affect ecosystem services and therefore human well-being; hence there is raising concern about the effects of multiple stressors on ecosystem services. Here, we review current perspectives on the linkages between multiple stressors and ecosystem services; research needs are highlighted to better comprehend these linkages in order to avoid impairments on human well-being.

Climate and land-use changes are posing increasing threats to freshwater-related ecosystem services, acting both on the supply and the demand side. A better understanding of the dynamics of these potential services, driven by the interactions between the factors mentioned above, could bring benefits to water resources management, the environment, and human well-being. In this work, we developed an integrated modeling approach to assess the conjoined impacts of land-use and climate changes on the potential ecosystem services (i.e. water yield and nutrients retention) until 2050. This approach was applied to the Taro River basin in Italy. Firstly, the results showed a 20% reduction in water yield was driven mainly by the increases in evapotranspiration demand and changes in rainfall patterns. Furthermore, a mean decrease of approximately 3% of the total nitrogen retention and a mean increase of 3% for the total phosphorus retention could be mainly attributed to land-use changes. Secondly, the rate of change would be different over time with the most pronounced differences between 2020 and 2030 and slower variations afterward. Finally, the obtained results could be a valuable support to identify and prioritize the best management practices for sustainable water use, balancing the tradeoffs among services.

Global change is severely impacting the biosphere that, through ecosystem services, sustains human well-being. Such impacts are expected to increase unless mitigation management actions are implemented. Despite the call from the scientific and political arenas for their implementation, few studies assess the effectiveness of actions on freshwater-related services. Here, by modeling water provisioning, water purification and erosion control under current and future conditions, we assess future trends of service provision with and without mitigation policies. In particular, two different storylines combine multiple climate, land use/land cover and agricultural management scenarios, and represent a pro-efficiency business as usual (myopic storyline) and a future that considers social and environmental sustainability (sustainable storyline). The mentioned services are modeled for the horizon 2050 and in three South European river basins: Ebro, Adige and Sava, which encompass the wide socio-environmental diversity of the region. Our results indicate that Mediterranean basins (Ebro) are extremely vulnerable to global change respect Alpine (Adige) or Continental (Sava) basins, as the Ebro might experience a decrease in water availability up to 40%, whereas the decrease is of only 2–4% in the Adige or negligible in the Sava. However, Mediterranean basins are also more sensitive to the implementation of mitigation actions, which would compensate the drop in water provisioning. Results also indicate that the regulating services of water purification and erosion control will gain more relevance in the future, as both services increased between 4 and 20% in both global change scenarios as a result of the expansion of agricultural and urban areas. Overall, the impact of global change is diverse among services and across river basins in Southern Europe, with the Mediterranean basins as the most vulnerable and the Continental as the least. The implementation of mitigation actions can compensate the impact and therefore deserves full political attention