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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.

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.

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.

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.

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.

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

Flow cessation affects river ecosystems submitted to low precipitation and increased water demand, and creates unfavourable conditions to aquatic biological communities. Diatoms are amongst the most sensitive biological groups to hydric stress, making them good indicators of preceding hydrological conditions. We here analyse the response of diatom assemblages to the duration and frequency of non-flow periods in 23 Mediterranean temporary streams. All of them experienced a strong decrease in water flow during summer, leading to a period of flow cessation. In addition, other ten permanent streams (zero dry days during the study period) were included in the study for comparative purposes. Temporary and permanent streams showed similar diatom species richness, evenness, and alpha diversity. However, beta diversity was higher in temporary than permanent streams, regardless rare taxa (

It is well established that a global sanitation crisis threatens humans. By comparison, much less attention has been given to address the effects of this crisis on the health of ecosystems. We provide examples of how sewage can affect natural ecosystems and where hotspots in sewage contamination commonly overlap with these habitats. We highlight these issues for some of the major ecosystems spanning across terrestrial, aquatic, and coastal realms. Recent studies reveal that untreated and poorly treated sewage elevates concentrations of nutrients, pathogens, endocrine disruptors, heavy metals, and pharmaceuticals in natural ecosystems. We show many large areas (10,000's of km2) across the globe with high levels of sewage contamination and that these contamination hotspots overlap extensively in occurrence with coral reefs, salt marshes, and fish-rich river systems. Given the global extent of sewage pollution in and near natural habitats, conservation biologists and managers must address this threat. However, because of its size, conservationists cannot solve this problem alone. We therefore argue that conservation must combine forces with the human health sector to create cross-disciplinary synergisms in innovation and efficiency. New sewage management solutions are emerging, such as waste-free toilets and resource recovery to generate fuel and drinking water; but more innovation is needed - a demand that will most effectively be reached through cross-sector collaboration.

Urban pollution and hydrological stress are common stressors of stream ecosystems, but their combined effects on ecosystem functioning are still unclear. We measured a set of functional processes and accompanying environmental variables in locations upstream and downstream of urban sewage inputs in 13 streams covering a wide range of water pollution levels and hydrological variability. Sewage inputs seriously impaired stream chemical characteristics and led to complex effects on ecosystem functioning. Biofilm biomass accrual, whole-reach nutrient uptake and metabolism (ecosystem respiration) were generally subsidized, whereas organic matter decomposition and biofilm phosphorus uptake capacity decreased with increasing pollutant concentrations. Hydrological stress affected stream ecosystem functioning but its effect was minor compared to the effects of urban pollution, due to the large inter-site variability of the streams. Changes appeared mainly linked to the concentration of pharmaceutically active compounds, followed by other chemical characteristics and by hydrology. The results point to the need to further improve sewage treatment, especially as climate change will stress riverine organisms and reduce the dilution capacity of the receiving streams.

Inland waters are significant sources of carbon dioxide (CO2) to the atmosphere. CO2 supersaturation and subsequent CO2 emissions from inland waters can be driven by internal metabolism, external inputs of dissolved inorganic carbon (DIC) derived from the catchment, and other processes (e.g., internal geochemical reactions of calcite precipitation or photochemical mineralization of organic solutes). However, the sensitivity of the magnitude and sources of CO2 emissions to fluvial network hydromorphological alterations is still poorly understood. Here we investigated both the magnitude and sources of CO2 emissions from lotic (i.e., running waters) and lentic (i.e., stagnant waters associated to small dams) waterbodies of a Mediterranean fluvial network by computing segment-scale mass balances of CO2. Our results showed that sources other than internal metabolism sustained most (82%) of the CO2 emissions from the studied fluvial network. The magnitude and sources of CO2 emissions in lotic waterbodies were highly dependent on hydrology, with higher emissions dominated by DIC inputs derived from the catchment during high flows and lower emissions partially fueled by CO2 produced biologically within the river during low flows. In contrast, CO2 emissions in lentic waterbodies were low, relatively stable over the time and the space, and dominated by DIC inputs from the catchment regardless of the different hydrological situations. Overall, our results stress the sensitivity of fluvial networks to human activities and climate change and particularly highlight the role of hydromorphological conditions on modulating the magnitude and sources of CO2 emissions from fluvial networks.

Current approaches have failed to deliver a truly integrated management of the different elements of the urban water system, such as freshwater ecosystems, drinking water treatment plants, distribution networks, sewer systems and wastewater treatment plants. Because the different parts of urban water have not been well integrated, poor decisions have been made for society in general, leading to the misuse of water resources, the degradation of freshwater ecosystems and increased overall treatment costs. Some attempts to solve environmental issues have adopted the ecosystem services concept in a more integrated approach, however this has rarely strayed far away from pure policy, and has made little impact in on-the-ground operational matters. Here, we present an improved decision-making framework to integrate the management of urban water systems. This framework uses the ecosystem service concept in a practical way to make a better use of both financial and water resources, while continuing to preserve the environment This research was supported by the European Communities 7thFramework Programme (SANITAS ITN Project agreement 289193); as well as by the individual fellowships Ramon y Cajal (RYC-2013-14595) and Marie Curie Career Integration Fellowship (PCIG9-GA-2011-293535) to Lluís Corominas, and a José Castillejo (CAS15-00163) to Vicenç Acuña. Authors also acknowledge the support from the Economy and Knowledge Department of the Catalan Government (Consolidated Research Group 2014 SGR 291 - ICRA).

Pharmaceuticals are designed to improve human and animal health, but may also be a threat to freshwater ecosystems, particularly after receiving urban or wastewater treatment plant (WWTP) effluents. Knowledge on the fate and attenuation of pharmaceuticals in engineered and natural ecosystems is rather fragmented, and comparable methods are needed to facilitate the comprehension of those processes amongst systems. In this study the dynamics of 8 pharmaceuticals (acetaminophen, sulfapyridine, sulfamethoxazole, carbamazepine, venlafaxine, ibuprofen, diclofenac, diazepam) and 11 of their transformation products were investigated in a WWTP and the associated receiving river ecosystem. During 3 days, concentrations of these compounds were quantified at the influents, effluents, and wastage of the WWTP, and at different distances downstream the effluent at the river. Attenuation (net balance between removal and release from and to the water column) was estimated in both engineered and natural systems using a comparable model-based approach by considering different uncertainty sources (e.g. chemical analysis, sampling, and flow measurements). Results showed that pharmaceuticals load reduction was higher in the WWTP, but attenuation efficiencies (as half-life times) were higher in the river. In particular, the load of only 5 out of the 19 pharmaceuticals was reduced by more than 90% at the WWTP, while the rest were only partially or non-attenuated (or released) and discharged into the receiving river. At the river, only the load of ibuprofen was reduced by more than 50% (out of the 6 parent compounds present in the river), while partial and non-attenuation (or release) was observed for some of their transformation products. Linkages in the routing of some pharmaceuticals (venlafaxine, carbamazepine, ibuprofen and diclofenac) and their corresponding transformation products were also identified at both WWTP and river. Finally, the followed procedure showed that dynamic attenuation in the coupled WWTP-river system could be successfully predicted with simple first order attenuation kinetics for most modeled compounds This research was supported by the European Communities 7th Framework Programme Marie Curie Career Integration Grant PCIG9-GA-2011-293535. Authors also acknowledge the support from the Economy and Knowledge Department of the Catalan Government (Consolidated Research Group 2014 SGR 291 - ICRA) and the Spanish Ministry of Economy and Competitiveness for funding (CTM2015- 66892-R, CTM2012-38314-C02-01 and RYC-2013-14595)

Decisions on river rehabilitation actions are often based on cost-benefit analyses taking into account the costs and benefits of the considered management actions, but ecosystem services are often not included as benefits, despite recent evidences on the effects of river rehabilitations on ecosystem services. A cost-benefit analysis integrating market and non-market costs and benefits was undertaken in this study to assess the economic feasibility of a river rehabilitation project in a water scarce region, the Yarqon River Rehabilitation project (Israel). In this case, the costs included both the capital costs of implementing rehabilitation measures (including maintenance costs) and the opportunity costs of water allocation (foregone benefits to farmers from water provisioning for agriculture). The benefits of rehabilitation included the net marginal benefits of the cultural ecosystem services at local scale (estimated with a hedonic pricing method), and at regional scale (estimated with a value function transfer), in addition to the habitat service gene-pool protection (estimated with a replacement cost method). Bearing in mind the uncertainties surrounding water resource management decisions, especially in water scarce areas, a sensitivity and risk analysis was conducted using an analysis that included both Monte Carlo simulations and the standardized regression coefficients method. The rehabilitation of the Yarqon River provided positive net present values (approximately $139 million in 30-year period). This was thanks to the provision of cultural ecosystem services and despite the high rehabilitation costs, and that the massive water reallocation involved high foregone benefits to farmers. Therefore, these results highlight that river rehabilitation in water scarce regions can be economically viable due to the social amenity demand for urban rivers This research was supported by EU-ITN SANITAS (ITN-289193), a Marie Curie European Reintegration Grant (PERG07-GA-2010-259219) and a Career Integration Grant (PCIG09-2011-293365) within the 7th European Community Framework Programme, and the RYC-2013-14595 from the Spanish Ministry of Economy and Competitiveness. Authors acknowledge the support from the Economy and Knowledge Department of the Catalan Government through Consolidated Research Group (2014 SGR 291) Catalan Institute for Water Research

Most fluvial networks worldwide include watercourses that recurrently cease to flow and run dry. The spatial and temporal extent of the dry phase of these temporary watercourses is increasing as a result of global change. Yet, current estimates of carbon emissions from fluvial networks do not consider temporary watercourses when they are dry. We characterized the magnitude and variability of carbon emissions from dry watercourses by measuring the carbon dioxide (CO2) flux from 10 dry streambeds of a fluvial network during the dry period and comparing it to the CO2 flux from the same streambeds during the flowing period and to the CO2 flux from their adjacent upland soils. We also looked for potential drivers regulating the CO2 emissions by examining the main physical and chemical properties of dry streambed sediments and adjacent upland soils. The CO2 efflux from dry streambeds (mean ± SD = 781.4 ± 390.2 mmol m−2 day−1) doubled the CO2 efflux from flowing streambeds (305.6 ± 206.1 mmol m−2 day−1) and was comparable to the CO2 efflux from upland soils (896.1 ± 263.2 mmol m−2 day−1). However, dry streambed sediments and upland soils were physicochemically distinct and differed in the variables regulating their CO2 efflux. Overall, our results indicate that dry streambeds constitute a unique and biogeochemically active habitat that can emit significant amounts of CO2 to the atmosphere. Thus, omitting CO2 emissions from temporary streams when they are dry may overlook the role of a key component of the carbon balance of fluvial networks This research was funded by the Spanish Ministry of Economy and Competitiveness through the Projects CGL2011-30474-C02-01 and CGL2014-58760-C3-1-R.

In-stream attenuation of dissolved and particulate forms of carbon, nitrogen and phosphorus are a crucial ecosystem service, especially in watercourses downstream of chemical pollution point-sources (i.e. wastewater treatment plants). Most chemical-fate models assume that attenuation is directly proportional to the concentration of available dissolved organic carbon, and inorganic nitrogen and phosphorus compounds in watercourses, but there are multiple evidences of saturation and even inhibition of attenuation at higher concentrations. Our current comprehension of nutrient attenuation kinetics in streams remains a limiting factor for the development and calibration of predictive models of the chemical fate of these compounds in rivers, thus hindering the development and implementation of more effective regulatory strategies. Here, we assessed the in-stream attenuation of dissolved organic carbon, inorganic nitrogen (NH4+, NO2-, NO3-) and phosphorus (PO43-) compounds at increasing concentrations of these compounds, and analyzed the interaction between attenuation kinetics and biofilm structure and function. Specifically, the net balances of these compounds were assessed in artificial streams exposed to eight treatments following the gradient of WWTP contribution to the river flow (0, 14, 29, 43, 58, 72, 86, and 100% of WWTP effluent water). Results indicate that biological in-stream attenuation by a given biofilm of an effluent dominated watercourse might be saturated if exposed for short periods to high nutrient concentrations such as during combined sewer overflow events, but that communities can adapt if exposed long enough to high concentrations, therefore avoiding or at least minimizing saturation. More attention should be therefore given to the management of effluent-dominated watercourses, as reductions in the temporal variability of the discharged wastewater by WWTP might enhance attenuation and thus reduce water quality issues downstream.

Organic micro-contaminants (OMCs) enter in freshwaters and interact with other contaminants such as carbon nanoparticles, becoming a problem of unknown consequences for river ecosystems. Carbon nanoparticles (as fullerenes C60) are good adsorbents of organic contaminants and their interaction can potentially affect their toxicity to river biofilms. We tested the C60 interactions with selected OMCs and their effects on river biofilms in different short-term experiments. In these, river biofilms were exposed to C60 and three OMCs (triclosan, diuron, or venlafaxine) and their respective mixtures with fullerenes (C60 + each OMC). The effects were evaluated on structural, molecular, and functional descriptors of river biofilms. Our results showed that C60 did not cause toxic effects in river biofilms, whereas diuron and triclosan significantly affected the heterotrophic and phototrophic components of biofilms and venlafaxine affected only the phototrophic component. The joint exposure of C60 with venlafaxine was not producing differences with respect to the former response of the toxicant, but the overall response was antagonistic (i.e., decreased toxicity) with diuron, and synergistic (i.e., increased toxicity) with triclosan. We suggest that differences in the toxic responses could be related to the respective molecular structure of each OMC, to the concentration proportion between OMC and C60, and to the possible competition between C60 pollutants on blocking the receptors of the biological cell membranes. We conclude that the presence of C60 at low concentrations modified the toxicity of OMC to river biofilms. These interactions should therefore be considered when predicting toxicity of OMC in river ecosystems. © 2018 Freixa, Acuña, Gutierrez, Sanchís, Santos, Rodriguez-Mozaz, Farré, Barceló and Sabater., We would like to thank Ferran Romero for his help in the molecular analysis, Lorenzo Proia for his help in using MicroResp technique, and Maria Casellas for laboratory assistance.

Inland waters substantially contribute to global carbon fluxes, and within them, low-order forested streams are important processors of allochthonous organic matter (OM) inputs. Leaf litter quantity and quality are expected to change in response to global change (e.g., climate change, land use change) but few long-term studies exist to better understand these shifts. The goal of this study was to assess the quantity and quality of OM sources to determine which global and local environmental factors control the dynamics of OM at the reach scale. The study was performed on a Mediterranean stream edged by a deciduous riparian forest over a 10-yr-time period. Riparian inputs, benthic and transported OM, and its carbon and nitrogen content were determined. The quantity of riparian inputs (912 ± 56 g dry mass m−2 yr−1) was comparable to temperate regions with deciduous riparian forests, but the Mediterranean climate determined the different dynamics of these inputs. El Nino Southern Oscillation was strongly related to the interannual variability in riparian inputs through changes in precipitation. The annual amount of inputs depended on previous cumulated nonflow periods, with successive nonflow periods causing a progressive decrease in riparian inputs. The distribution of inputs throughout the year followed either a unimodal or bimodal pattern according to the absence or presence of a nonflow period in summer. In addition, drought caused lower quality (higher carbon : nitrogen molar ratio) riparian inputs. Changes in the quantity and quality of OM were explained by both present and past local and global factors.

During summer drought, Mediterranean fluvial networks are transformed into highly heterogeneous landscapes characterized by different environments (i.e., running and impounded waters, isolated river pools and dry beds). This hydrological setting defines novel biogeochemically active areas that could potentially increase the rates of carbon emissions from the fluvial network to the atmosphere. Using chamber methods, we aimed to identify hot spots for carbon dioxide (CO2) and methane (CH4) emissions from two typical Mediterranean fluvial networks during summer drought. The CO2 efflux from dry beds (mean ± SE = 209 ± 10 mmolCO2m-2 d-1) was comparable to that from running waters (120 ± 33 mmol m-2 d-1) and significantly higher than from impounded waters (36.6 ± 8.5 mmol m-2 d-1) and isolated pools (17.2 ± 0.9 mmol m-2 d-1). In contrast, the CH4 efflux did not significantly differ among environments, although the CH4 efflux was notable in some impounded waters (13.9 ± 10.1 mmol CH4 m-2 d-1) and almost negligible in the remaining environments (mean\0.3 mmol m-2 d-1). Diffusion was the only mechanism driving CO2 efflux in all environments and was most likely responsible for CH4 efflux in running waters, isolated pools and dry beds. In contrast, the CH4 efflux in impounded waters was primarily ebullition-based. Using a simple heuristic approach to simulate potential changes in carbon emissions from Mediterranean fluvial networks under future hydrological scenarios, we show that an extreme drying out (i.e., a four-fold increase of the surface area of dry beds) would double the CO2 efflux from the fluvial network. Correspondingly, an extreme transformation of running waters into impounded waters (i.e., a twofold increase of the surface area of impounded waters) would triple the CH4 efflux. Thus, carbon emissions from dry beds and impounded waters should be explicitly considered in carbon assessments of fluvial networks, particularly under predicted global change scenarios, which are expected to increase the spatial and temporal extent of these environments This research was funded by the Spanish Ministry of Economy and Competitiveness through the projects CGL2011-30474-C02-01 and CGL2014-58760-C3-1-R

Current trends indicate that the duration of the period with no surface flow experienced by temporary waterways is increasing. Even though several studies have already characterised the effects of non-flow periods on stream ecosystems, the consequences of their increasing duration remain poorly understood. Replicate artificial streams were used to characterise the effects of the duration of the non-flow period on stream biofilm processes. We hypothesised that increased duration of the non-flow period would differentially influence autotrophic and heterotrophic processes and promote heterotrophy (lower P: R ratios). We aimed to identify possible non-linearities and thresholds in the disturbance-response relationships between the duration of the non-flow period (six treatments) and stream biofilm processes (six ecological variables representing autotrophic or heterotrophic processes). The duration of the non-flow period proved to be important for the balance between autotrophic and heterotrophic processes in stream biofilms, with the autotrophic processes being less resistant but more resilient. Autotrophic and heterotrophic processes also differed in terms of disturbance-response relationships, which were linear for most autotrophic ecological variables and sigmoid logistic for heterotrophic variable. Hence, non-flow periods had an immediate effect on autotrophic processes, but the effect on heterotrophic processes was delayed and completed only after crossing the ecological threshold of complete desiccation. These differences involved a shift towards lower P: R ratios at longer durations of the non-flow period. However, the high resilience of autotrophic processes, mainly related to the ability of diatoms to recover, limited the shift towards lower P: R ratios to the non-flow period and to the first weeks after flow return. This study demonstrates the complex effects of flow intermittency on stream biofilm processes, and emphasises the relevance of the duration of the non-flow period as a predictor of the effects on temporary waterways This research was supported by a Marie Curie European Reintegration Grant (PERG07-GA-2010-259219) within the 7th European Community Framework Programme, by the Spanish Ministry of Economy and Competitiveness through its financial support through the project CARBONET (CGL2011-30474-C02-01) and by the European Union through the European Regional Development Fund (FEDER)

Aquatic organisms from freshwater ecosystems impacted by waste water treatment plant (WWTP) effluents are constantly exposed to constant concentrations of pharmaceuticals, endocrine disruptors and related compounds, among other anthropogenic contaminants. Macroinvertebrates inhabiting freshwater ecosystems might be useful bioindicators of exposure to contaminants, since their lives are long enough to bioaccumulate, but at the same time may integrate short-term changes in the environment. However, studies about potential bioaccumulation of emerging contaminants in these organisms are very scarce. The objectives of this study were to develop an analytical methodology for the analysis of 41 pharmaceuticals and 21 endocrine disruptors in freshwater invertebrates. In addition, bioaccumulation of these contaminants in three macroinvertebrate taxa inhabiting a waste water treatment plant -impacted river was evaluated. The method for the simultaneous extraction of both families of compounds is based on sonication, purification via removal of phospholipids, and analysis by ultra performance liquid chromatography coupled to a mass spectrometer (UPLC-MS/MS) in tandem. Recoveries for pharmaceuticals were 34-125%, and for endocrine disruptors were 48-117%. Method detection limits (MDLs) for EDCs were in the range of 0.080-2.4 ng g-1, and for pharmaceuticals, 0.060-4.3 ng g-1. These pollutants were detected in water samples taken downstream the waste water treatment plant effluent at concentrations up to 572 ng L-1. Two non-esteroidal anti-inflammatory drugs, diclofenac and ibuprofen, and four endocrine disruptors - estrone, bisphenol A, TBEP, and nonylphenol - were detected in at least one macroinvertebrate taxa in concentrations up to 183 ng g-1 (dry weight). An isobaric interference was identified during the analysis of diclofenac in Hydropsyche samples, which was successfully discriminated via accurate mass determination by TFC-LTQ Orbitrap This study has been financed by Spanish Ministry o fEconomy and Competitiveness through the project SCARCE (Consolider-Ingenio 2010CSD200900065). This work was partly supported by the Generalitat de Catalunya (Consolidated Research Group: Catalan Institute for water Research 2014 SGR 291)

Freshwater ecosystems are confronted with multiple chemical, biological and physical stressors. Co-occurring stressors commonly result in additive responses, but non-additive interactions may also occur, hindering our predicting capacity. Despite growing interest in multiple stressor research, the response of freshwater communities to co-occurring chemical and climate change-related physical stressors remains largely unexplored. Here, we used a microcosm approach to evaluate the effect of the combined action of chemical and physical stressors on river biofilms. Results showed that additive responses dominated, whereas 14.5% of all responses were non-additive (75% antagonisms and 25% synergisms). Among these non-additive interactions, physical stressors dominated over chemicals and drove the overall responses. Overall, the occurrence of these non-additive interactions, together with the dominance of the climate-change related physical stressors, might lead to unexpected responses as a result of climate change.

Wastewater effluents increase the nutrient load of receiving streams while introducing a myriad of anthropogenic chemical pollutants that challenge the resident aquatic (micro)biota. Disentangling the effects of both kind of stressors and their potential interaction on the dissemination of antibiotic resistance genes in bacterial communities requires highly controlled manipulative experiments. In this work, we investigated the effects of a combined regime of nutrients (at low, medium and high concentrations) and a mixture of emerging contaminants (ciprofloxacin, erythromycin, sulfamethoxazole, diclofenac, and methylparaben) on the bacterial composition, abundance and antibiotic resistance profile of biofilms grown in artificial streams. In particular, we investigated the effect of this combined stress on genes encoding resistance to ciprofloxacin (qnrS), erythromycin (ermB), sulfamethoxazole (sul1 and sul2) as well as the class 1 integron-integrase gene (intI1). Only genes conferring resistance to sulfonamides (sul1 and sul2) and intI1 gene were detected in all treatments during the study period. Besides, bacterial communities exposed to emerging contaminants showed higher copy numbers of sul1 and intI1 genes than those not exposed, whereas nutrient amendments did not affect their abundance. However, bacterial communities exposed to both emerging contaminants and a high nutrient concentration (1, 25 and 1 mg L−1 of phosphate, nitrate and ammonium, respectively) showed the highest increase on the abundance of sul1 and intI1 genes thus suggesting a factors synergistic effect of both stressors. Since none of the treatments caused a significant change on the composition of bacterial communities, the enrichment of sul1 and intI1 genes within the community was caused by their dissemination under the combined pressure exerted by nutrients and emerging contaminants. To the best of our knowledge, this is the first study demonstrating the contribution of nutrients on the maintenance and spread of antibiotic resistance genes in streambed biofilms under controlled conditions. Our results also highlight that nutrients could enhance the effect of emerging contaminants on the dissemination of antibiotic resistance.

A mesocosm case study was conducted to gain understanding and practical knowledge on biofilm emerging contaminants biodegradation capacity under stressor and multiple stressor conditions. Two real life scenarios: I) biodegradation in a pristine intermittent stream experiencing acute pollution and II) biodegradation in a chronically polluted intermittent stream, were examined via a multifactorial experiment using an artificial stream facility. Stream biofilms were exposed to different water flow conditions i.e. permanent and intermittent water flow. Venlafaxine, a readily biodegradable pharmaceutical was used as a measure of biodegradation capacity while pollution was simulated by a mixture of four emerging contaminants (erythromycin, sulfisoxazole, diclofenac and imidacloprid in addition to venlafaxine) in environmentally relevant concentrations. Biodegradation kinetics monitored via LC-MS/MS was established, statistically evaluated, and used to link biodegradation with stress events. The results suggest that the effects of intermittent flow do not hinder and may even stimulate pristine biofilm biodegradation capacity. Chronic pollution completely reduced biodegradation in permanent water flow experimental treatments while no change in intermittent streams was observed. A combined effect of water flow conditions and emerging contaminants exposure on biodegradation was found. The decrease in biodegradation due to exposure to emerging contaminants is significantly greater in streams with permanent water flow suggesting that the short and medium term biodegradation capacity in intermittent systems may be preserved or even greater than in perennial streams.