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Intact peatlands provide hydrological ecosystem services, such as regulating water regimes and immobilizing pollutants within catchments. Climate change impacts including drought and wildfire may impair their functioning, potentially impacting ecosystem service delivery. Here we investigate stream water quality changes following the combined impacts of a summer drought and wildfire in a peat‐dominated catchment in the UK during 2018. The study catchment stores legacy pollutants (i.e., metals) due to past industrial activity, thus making it particularly susceptible to pollutant release during wildfires. We quantified changes in water chemistry during five storm events over a 9‐month period following the wildfire. Concentration‐discharge (C‐Q) relationships for nine solutes were analyzed to explore changes in activation and connectivity of solute source zones. Hysteresis and flushing indices of C‐Q responses further described solute dynamics during storm events. We found that most nutrient and base cation concentrations in the stream discharge were highest in the immediate post‐fire storm events and decreased during subsequent autumn and spring storms. Metal concentrations increased during autumn and spring storms, indicating delayed mobilization from within‐peat or distal headwater sources. Our findings suggest that seasonal re‐wetting and hydrologic connectivity following disturbance influenced solute source zone activation and transport in the study catchment. Water quality responses associated with wildfire and drought were primarily observed in the months following the wildfire, suggesting mobilization of pollutants peaks shortly after fire. Our results contribute to a critical understanding of the future of water quality risks in temperate peatland catchments subject to disturbances exacerbated by climate change. Plain Language Summary: Peatlands are defined by their accumulated organic matter, providing valuable natural services such as storing carbon, and regulating climate, water quality and runoff. Such capability may be reduced when peatlands are impacted by extreme wildfires and droughts. We studied impacts of a severe wildfire and drought on stream water quality in a peatland catchment in the UK, within a region that may be more frequently impacted by these events in the future due to changing climate. This peatland also stores pollutants (namely metals emitted and retained during the industrial revolution), further enhancing risks to drinking water quality. We determined how the wildfire affected instream chemistry post‐fire, and how nutrients and metals moved through the catchment. We found that levels of nutrients in the stream flow increased immediately after the wildfire, followed by a decrease with time. However, the levels of metals increased during the following autumn and spring. This suggests that metals were released later and came from different parts of the catchment compared to the nutrients. Our results show that following the fire, the way water flowed through the catchment played an important role in how substances were transported. The impacts on water quality were most pronounced in the first months post‐wildfire and seemed to be short‐lived. Key Points: Nutrients and base cation streamflow concentrations were elevated following wildfire, and decreased in autumn and spring storm eventsMetals in the catchment showed delayed mobilization, indicating distal headwater source zones rather than proximal to stream sourcesSeasonal re‐wetting after drought enhanced catchment hydrologic connectivity, influencing source zone activation and transport [ABSTRACT FROM AUTHOR]

Improved monitoring of potable water is essential if we are to achieve the UN Sustainable Development Goals (SDGs), specifically SDG6: to make clean water and sanitation available to all. Typically monitoring of potable water requires laboratory analysis to detect indicators of fecal pollution, such as thermotolerant coliforms (TTCs), Escherichia coli (E. coli), or intestinal enterococci. However, these analyses are time‐consuming and expensive, and recent advances in field deployable sensing technology offer opportunities to investigate both the spatial and temporal dynamics of microbial pollution in a more resolved and cost‐effective manner, thus advancing process‐based understanding and practical application for human health. Fluorescence offers a realistic proxy for monitoring coliforms in freshwaters with potential for quantification of potable water contamination in near real‐time with no need for costly reagents. Here, we focus on E. coli to provide a state‐of‐the‐art review of potential technologies capable of delivering an effective real‐time E. coli sensor system. We synthesize recent research on the use of fluorescence spectroscopy to quantify microbial contamination and discuss a variety of approaches (and constraints) to relate the raw fluorescence signal to E. coli enumerations. Together, these offer an invaluable platform to monitor drinking water quality which is required in situations where the water treatment and distribution infrastructure is degraded, for example in less economically developed countries; and during disaster‐relief operations. Overall, our review suggests that the fluorescence of dissolved organic matter is the most viable current method—given recent advances in field‐deployable technology—and we highlight the potential for recent developments to enhance approaches to water quality monitoring. This article is categorized under:Engineering Water > Water, Health, and SanitationEngineering Water > MethodsHuman Water > Methods [ABSTRACT FROM AUTHOR]

In the face of intermeshed phases of pollutants, we need compressed and overlapping solutions that: Integrate understanding of human activity into holistic water management To address complex water quality challenges, rivers and their hinterlands must be managed as connected systems. We propose river pollution can be conceptualized in three historical "Phases", characterized by distinct contaminant types and mitigation methods: Phase 1. FROM CRISIS TO SOLUTIONS The last two centuries of water problems and solutions (Figure 2) demonstrate that we must be proactive in managing river pollution rather than create new pollution legacies for future generations. Growing pollutant knowledge has improved regulation with more stringent standards Although the widespread detection of long-banned pollutants such as Polychlorinated biphenyls could signal worsening pollution, often it reflects improved measurement capabilities. [Extracted from the article]

The global increase of urban impervious land cover poses a significant threat to the integrity of river ecosystems. Hence, it is critical to assess the efficiency of green roofs (GR) to mitigate the negative impacts of urbanization on river ecosystems, such as thermal surges and pollutants. In this study, we evaluated the ecohydrological behaviour of two fully established GR under differing management regimes at the Chicago Botanical Gardens from July to September 2019. The drainage outflow from a non‐vegetated roof, a managed GR (perennial native and non‐native plants) and an unmanaged GR (perennial natural prairie vegetation) were monitored, and thermal dynamics, dissolved organic matter (DOM) composition and nitrate concentration assessed. The managed GR runoff had a lower DOC concentration and less humic‐like DOM signal (SUVA254) compared to the unmanaged GR. In contrast, lower concentrations of nitrate and more recalcitrant DOM (less protein‐like compounds relative to humic‐like compounds) were associated with the unmanaged GR. The unmanaged GR also displayed a greater capacity to reduce thermal surges associated with storm events. Our study provides new information on the implications of GR management for water quality with particular relevance to the urban stream syndrome. Further, the impacts of GR management on the mitigation of thermal surges and DOM composition can help to improve future GR design, as these ecohydrological responses have been largely overlooked to date. Our findings can support future urban planning, particularly for scenarios where green infrastructures are used to mitigate the impacts of climate change on urban river ecosystems. [ABSTRACT FROM AUTHOR]

The appeal of trait‐based approaches for assessing environmental vulnerabilities arises from the potential insight they provide into the mechanisms underlying the changes in populations and community structure. Traits can provide ecologically based explanations for observed responses to environmental changes, along with predictive power gained by developing relationships between traits and environmental variables. Despite these potential benefits, questions remain regarding the utility and limitations of these approaches, which we explore focusing on the following questions: (a) How reliable are predictions of biotic responses to changing conditions based on single trait–environment relationships? (b) What factors constrain detection of single trait–environment relationships, and how can they be addressed? (c) Can we use information on meta‐community processes to reveal conditions when assumptions underlying trait‐based studies are not met? We address these questions by reviewing published literature on aquatic invertebrate communities from stream ecosystems. Our findings help to define factors that influence the successful application of trait‐based approaches in addressing the complex, multifaceted effects of changing climate conditions on hydrologic and thermal regimes in stream ecosystems. Key conclusions are that observed relationships between traits and environmental stressors are often inconsistent with predefined hypotheses derived from current trait‐based thinking, particularly related to single trait–environment relationships. Factors that can influence findings of trait‐based assessments include intercorrelations of among traits and among environmental variables, spatial scale, strength of biotic interactions, intensity of habitat disturbance, degree of abiotic stress, and methods of trait characterization. Several recommendations are made for practice and further study to address these concerns, including using phylogenetic relatedness to address intercorrelation. With proper consideration of these issues, trait‐based assessment of organismal vulnerability to environmental changes can become a useful tool to conserve threatened populations into the future. [ABSTRACT FROM AUTHOR]

Predicted trends towards more intense droughts are of particular significance for running water ecosystems, as the loss of critical stream habitat can provoke sudden changes in biodiversity and shifts in community structure. However, analysing ecological responses to the progressive loss of stream habitat requires a continuous disturbance gradient that can only be generated through large‐scale manipulations of streamflow.In the first experiment of its kind, we used large artificial stream channels (mesocosms) as analogues of spring‐fed headwaters and simulated a gradient of drought intensity that encompassed flowing streams, disconnected pools, and dry streambeds. We used breakpoint analysis to analyse macroinvertebrate community responses to intensifying drought, and identify the taxa and compositional metrics sensitive to small changes in drought stress.We detected breakpoints for >60% of taxa, signalling sudden population crashes or irruptions as drought intensified. Abrupt changes were most pronounced where riffle dewatering isolated pools. In the remnant wetted habitat, we observed a shift to larger body sizes across the community, primarily driven by irruptions of predatory midge larvae and coincident population collapses among prey species (worms and smaller midges).Our results suggest that intense predation in confined, fragmented stream habitat can lead to unexpected changes in body sizes, challenging the conventional wisdom that droughts favour the small. Pool fragmentation might thus be the most critical stage of habitat loss during future droughts, as the point at which impacted rivers and streams begin to exhibit major shifts in fundamental food web properties. [ABSTRACT FROM AUTHOR]

Functional traits are increasingly being used to predict extinction risks and range shifts under long‐term climate change scenarios, but have rarely been used to study vulnerability to extreme climatic events, such as supraseasonal droughts. In streams, drought intensification can cross thresholds of habitat loss, where marginal changes in environmental conditions trigger disproportionate biotic responses. However, these thresholds have been studied only from a structural perspective, and the existence of functional nonlinearity remains unknown. We explored trends in invertebrate community functional traits along a gradient of drought intensity, simulated over 18 months, using mesocosms analogous to lowland headwater streams. We modelled the responses of 16 traits based on a priori predictions of trait filtering by drought, and also examined the responses of trait profile groups (TPGs) identified via hierarchical cluster analysis. As responses to drought intensification were both linear and nonlinear, generalized additive models (GAMs) were chosen to model response curves, with the slopes of fitted splines used to detect functional thresholds during drought. Drought triggered significant responses in 12 (75%) of the a priori‐selected traits. Behavioural traits describing movement (dispersal, locomotion) and diet were sensitive to moderate‐intensity drought, as channels fragmented into isolated pools. By comparison, morphological and physiological traits showed little response until surface water was lost, at which point we observed sudden shifts in body size, respiration mode and thermal tolerance. Responses varied widely among TPGs, ranging from population collapses of non‐aerial dispersers as channels fragmented to irruptions of small, eurythermic dietary generalists upon extreme dewatering. Our study demonstrates for the first time that relatively small changes in drought intensity can trigger disproportionately large functional shifts in stream communities, suggesting that traits‐based approaches could be particularly useful for diagnosing catastrophic ecological responses to global change. A growing number of studies are using species' traits to diagnose and predict their responses to long‐term climate change, but few have explored trait sensitivity to extreme climatic events, such as prolonged droughts. We combined a large manipulative flow experiment with traits‐based analyses to elucidate functional responses of stream macroinvertebrate communities to intensifying drought. Drought caused abrupt and pervasive changes in community trait profiles and triggered population collapses of certain functional groups, most notably those comprising non‐flying taxa. Our detection of multiple response thresholds indicates that traits could be valuable functional biomarkers for species‐ and community‐level resistance to extreme disturbance. [ABSTRACT FROM AUTHOR]

Climatic extremes are becoming more frequent and intense across much of the globe, potentially transforming the biodiversity and functioning of affected ecosystems. In freshwaters, hydrological extremes such as drought can regulate beta diversity, acting as powerful environmental filters to dictate the complement of species and functional traits found at local and landscape scales. New methods that enable beta diversity and its functional equivalent to be partitioned into turnover (replacement of species/functions) and nestedness‐resultant (gain/loss of species/functions) components may offer novel insights into the parallel impacts of drought on ecosystem structure and function. Using a series of artificial channels (mesocosms) designed to mimic perennial headwater streams, we experimentally manipulated streamflows to simulate a gradient of drought intensity. We then modelled taxonomic and functional turnover and nestedness of macroinvertebrate communities along this gradient, validating direct gradient approaches (bootstrapping, Mantel tests) against null models of nestedness. Drought intensification produced significant environmental distance decay trends (i.e. communities became increasingly taxonomically and functionally dissimilar the more differentially disturbed by drought they were). Taxonomic distance decay was primarily driven by turnover, while the functional trend reflected a combination of richness differences and turnover at different points along the gradient. Taxonomic and functional distance decay slopes were not significantly different, implying that communities were functionally vulnerable to drying. The increased frequency and intensity of droughts predicted under most climate change scenarios could thus profoundly modify not only the structure of running water invertebrate communities, but also the ecosystem functions they underpin. [ABSTRACT FROM AUTHOR]

Storm events can drive highly variable behavior in catchment nutrient and water fluxes, yet short-term event dynamics are frequently missed by low-resolution sampling regimes. In addition, nutrient source zone contributions can vary significantly within and between storm events. Our inability to identify and characterize time-dynamic source zone contributions severely hampers the adequate design of land use management practices in order to control nutrient exports from agricultural landscapes. Here we utilize an 8 month high-frequency (hourly) time series of streamflow, nitrate (NO3-N), dissolved organic carbon (DOC), and hydroclimatic variables for a headwater agricultural catchment. We identified 29 distinct storm events across the monitoring period. These events represented 31% of the time series and contributed disproportionately to nutrient loads (42% of NO3-N and 43% of DOC) relative to their duration. Regression analysis identified a small subset of hydroclimatological variables (notably precipitation intensity and antecedent conditions) as key drivers of nutrient dynamics during storm events. Hysteresis analysis of nutrient concentration-discharge relationships highlighted the dynamic activation of discrete NO3-N and DOC source zones, which varied on an event-specific basis. Our results highlight the benefits of high-frequency in situ monitoring for characterizing short-term nutrient fluxes and unraveling connections between hydroclimatological variability and river nutrient export and source zone activation under extreme flow conditions. These new process-based insights, which we summarize in a conceptual model, are fundamental to underpinning targeted management measures to reduce nutrient loading of surface waters. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) quality and quantity is not measured routinely in-situ limiting our ability to quantify DOM process dynamics. This is problematic given legislative obligations to determine event based variability; however, recent advances in field deployable optical sensing technology provide the opportunity to address this problem. In this paper, we outline a new approach for in-situ quantification of DOM quantity (Dissolved Organic Carbon: DOC) and a component of quality (Biochemical Oxygen Demand: BOD) using a multi-wavelength, through-flow fluorescence sensor. The sensor measured tryptophan-like (Peak T) and humic-like (Peak C) fluorescence, alongside water temperature and turbidity. Laboratory derived coefficients were developed to compensate for thermal quenching and turbidity interference (i.e., light attenuation and scattering). Field tests were undertaken on an urban river with ageing wastewater and stormwater infrastructure (Bourn Brook; Birmingham, UK). Sensor output was validated against laboratory determinations of DOC and BOD collected by discrete grab sampling during baseflow and stormflow conditions. Data driven regression models were then compared to laboratory correction methods. A combination of temperature and turbidity compensated Peak T and Peak C was found to be a good predictor of DOC concentration ( R2 = 0.92). Conversely, using temperature and turbidity correction coefficients provided low predictive power for BOD ( R2 = 0.46 and R2 = 0.51, for Peak C and T, respectively). For this study system, turbidity appeared to be a reasonable proxy for BOD, R2 = 0.86. However, a linear mixed effect model with temperature compensated Peak T and turbidity provided a robust BOD prediction ( R2 = 0.95). These findings indicate that with careful initial calibration, multi-wavelength fluorescence, coupled with turbidity, and temperature provides a feasible proxy for continuous, in-situ measurement of DOC concentration and BOD. This approach represents a cost effective monitoring solution, particularly when compared to UV - absorbance sensors and DOC analysers, and could be readily adopted for research and industrial applications. [ABSTRACT FROM AUTHOR]

In alpine river networks, water source (i.e. snow, ice or groundwater) plays a major role in influencing flow regimes, benthic habitat and macro-invertebrate community structure. Across these systems, a natural stress gradient can be conceptualized, from rivers fed exclusively by meltwater (harsh habitat) to those with no melt input (relatively benign, groundwater fed). However, despite the current context of rapid glacier retreat, our understanding of linkages between meltwater contributions, physico-chemical habitat and biodiversity remains limited. To address this research gap, habitat characteristics and macro-invertebrate community structure were studied at 26 sites (five river basins) in the French Pyrénées across a meltwater gradient from 0% to 99%. A combination of generalized regression models and multivariate analyses showed that the stress gradient was associated with the following: (i) linear responses of key physico-chemical habitat variables, in particular bed stability, (ii) unimodal responses at the community level (e.g. richness and total density peaks at 40-60% meltwater contribution), and (iii) both unimodal and monotonic responses at the level of individual taxa. Sites characterized by high contributions of meltwater, although species poor, were important for beta diversity because of their specialist endemic fauna. Our findings suggest that continued glacier and snowpack retreat due to expected future climate change are likely to lead to more homogeneous alpine river habitats (i.e. reduced meltwater-groundwater stress gradient breadth). As a result, increased alpha diversity is expected as previously harsh habitats become more favourable; however, an associated decrease in beta diversity is likely as glacial stream specialists become replaced by generalists. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT Aim Small (< 1 km2) alpine glaciers are likely to disappear in this century, resulting in decreased regional habitat heterogeneity in associated streams. Both heterogeneity within and spatial isolation among glacier-influenced streams can enhance beta diversity of stream-dwelling organisms. We measured beta at both community and population-genetic levels within and among streams currently influenced by small Pyrenean glaciers. We aimed to evaluate whether patterns are analogous between the two levels, to apply various approaches for characterizing beta, and to infer the outcome of future glacier loss on regional biodiversity. Location Four glacier-fed basins in the Parc National des Pyrénées, France. Methods We classified each of 18 stream reaches across the basins into either high-, mid- or low-'glaciality' (glacial influence) groups according to four physicochemical characteristics. At each reach, we collected macroinvertebrate communities and evaluated mitochondrial DNA haplotypes for 11-13 individuals of Baetis alpinus Pictet. Using taxa/haplotypes as basic units, we evaluated community and population-genetic beta diversity simultaneously. We measured beta diversity in three major ways: as multivariate (Sørensen's dissimilarity, Jost D) and 'classical' (gamma/alpha) variation to compare among glaciality groups, and as turnover along the glaciality gradient within each basin. Results For most approaches at both organizational levels, beta was greatest among high-glaciality reaches, absolute values of variation of beta in high-glaciality streams were strikingly similar between levels, and the steepest turnover within basins occurred between high- and mid-glaciality reaches. Therefore, high-glaciality reaches contained assemblages and populations that were unique both within that stream type (among basins) and compared with other stream types within basins. Main conclusions Parallel beta diversity patterns at population-genetic and community levels suggested that environmental drivers influence these levels analogously. Extreme conditions (e.g. low temperature, high instability, isolation) in high-glaciality streams probably enhance beta at both levels. Stream beta diversity is likely to decrease substantially with continued glacial reduction in this system. [ABSTRACT FROM AUTHOR]