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Our study aimed to determine drivers of longitudinal variation in stream metabolism and benthic macroinvertebrate (BMI) composition and assess concordance of these ecological measures for two Canadian rivers (Rat River and Tobacco Creek). Gross primary production was associated with longitudinal position in both rivers but also with the percentage of the watershed used for agriculture and hydrogeomorphic zone. However, within- and among-zone differences in stream metabolism indicated that longitudinal variation followed a staircase pattern rather than a clinal pattern. BMI composition was associated with network position in both rivers, but hydrogeomorphic zones were only important in Tobacco Creek. Among-zone differences in BMI communities in Tobacco Creek depended on season. Concordance between stream metabolism and BMI composition was not observed within either river despite metabolism and BMI composition being associated with longitudinal position. For these rivers, segment-scale hydrogeomorphic conditions appear to be important modifiers of longitudinal patterns observed at the whole river scale. The lack of concordance between stream metabolism and BMI composition suggests reach-scale processes are driving ecological differences within sampling sites. Notre etude visait a determiner les facteurs de variation longitudinale du metabolisme des eaux et de la composition des macroinvertebres benthiques (MIB) et a evaluer la concordance de ces parametres ecologiques pour deux rivieres canadiennes (la riviere Rat et le Tobacco Creek). La production primaire brute est associee a la position longitudinale dans les deux rivieres, mais egalement au pourcentage du bassin versant utilise pour l'agriculture et la zone hydrogeomorphologique. Les differences au sein des zones et entre elles sur le plan du metabolisme des eaux indiquent toutefois que la variation longitudinale suit un motif en escalier plutot qu'un motif clinal. La composition des MIB est associee a la position dans le reseau pour les deux rivieres, mais les zones hydrogeomorphologiques ne sont importantes que dans le Tobacco Creek. Les differences entre zones des communautes de MIB dans le Tobacco Creek dependent de la saison. Une concordance entre le metabolisme des eaux et la composition des MIB n'est observee dans aucune des deux rivieres malgre le fait que le metabolisme et la composition des MIB soient associes a la position longitudinale. Pour ces rivieres, les conditions hydrogeomorphologiques a l'echelle du tronqon semblent etre d'importants modificateurs des motifs longitudinaux observes a l'echelle de la riviere. L'absence de concordance entre le metabolisme des eaux et la composition des MIB porte a croire que des processus a l'echelle du tronqon expliqueraient les differences ecologiques dans les sites d'echantillonnage. [Traduit par la Redaction], Introduction Detecting patterns of ecological condition in lotic systems and then discerning the processes that regulate these patterns are critical steps towards effective management of aquatic resources. According to the [...]

Rivers suffer from multiple stressors acting simultaneously on their biota, but the consequences are poorly quantified at the global scale. We evaluated the biological condition of rivers globally, including the largest proportion of countries from the Global South published to date. We gathered macroinvertebrate‐ and fish‐based assessments from 72,275 and 37,676 sites, respectively, from 64 study regions across six continents and 45 nations. Because assessments were based on differing methods, different systems were consolidated into a 3‐class system: Good, Impaired, or Severely Impaired, following common guidelines. The proportion of sites in each class by study area was calculated and each region was assigned a Köppen‐Geiger climate type, Human Footprint score (addressing landscape alterations), Human Development Index (HDI) score (addressing social welfare), % rivers with good ambient water quality, % protected freshwater key biodiversity areas; and % of forest area net change rate. We found that 50% of macroinvertebrate sites and 42% of fish sites were in Good condition, whereas 21% and 29% were Severely Impaired, respectively. The poorest biological conditions occurred in Arid and Equatorial climates and the best conditions occurred in Snow climates. Severely Impaired conditions were associated (Pearson correlation coefficient) with higher HDI scores, poorer physico‐chemical water quality, and lower proportions of protected freshwater areas. Good biological conditions were associated with good water quality and increased forested areas. It is essential to implement statutory bioassessment programs in Asian, African, and South American countries, and continue them in Oceania, Europe, and North America. There is a need to invest in assessments based on fish, as there is less information globally and fish were strong indicators of degradation. Our study highlights a need to increase the extent and number of protected river catchments, preserve and restore natural forested areas in the catchments, treat wastewater discharges, and improve river connectivity. [ABSTRACT FROM AUTHOR]

Municipal wastewater lagoons are common across North America and, unlike larger mechanical wastewater treatment plants, typically release nutrient-rich effluent directly to rivers in intermittent pulses. However, little is known about the fate of nutrients from these episodic events, which may happen under varying hydrologic or thermal conditions. We assessed fate of nitrogen (N) and phosphorus (P) from lagoon effluent during three releases to Deadhorse Creek, Manitoba, Canada. Using net nutrient uptake lengths and natural abundance stable isotope ratios of dissolved inorganic nitrogen (DIN) and primary producers, we found that DIN was processed during the summer releases though the dominant mechanism was unclear. However, nitrate was largely exported in autumn. Primary producers assimilated lagoon N but did not appear to reduce DIN concentrations. The longitudinal pattern of soluble reactive phosphorus (SRP) varied between releases and in summer 2019 the stream became a net source of SRP despite concomitant processing of DIN. We hypothesize that low demand for P in Deadhorse Creek, as suggested by upstream SRP > 0.05 mg P L−1, and nutrient ratios indicative of N limitation, reduced instream processing of P. Furthermore, our results indicated that cool or high flow conditions may result in the export of much of the lagoon nutrient load downstream. Our findings suggest the processes that transform wastewater nutrients are overwhelmed during effluent releases. Managers should consider increasing effluent dilution via continuous release of effluent rather than pulsed delivery. However, management of upstream nutrient supply may also be needed when relying upon the self-purifying capacity of rivers. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Water Resources Journal / Revue Canadienne des Ressources Hydriques is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

There has been a trend toward increasing anthropocentrism in definitions of river health through the explicit inclusion of societal valuation of ecosystem services provided by rivers. New frameworks and associated indicators of river health are therefore required to centralize ecosystem services within river assessment and management activities. Here, we adopt an anthropocentric conceptualization of rivers to focus on a river's ability to maintain ecological function and structure that support ecosystem services valued by society. We apply this approach to further existing conceptual models of river assessment by identifying how benthic indicators can be linked to valued ecosystem services in a river services assessment framework. This approach extends bioassessment from a focus on assessing departure from reference condition to also include the evaluation of rivers based on their delivery of ecosystem services. Indicators based on benthic processes and assemblages are widely used in river health assessments; thus, these are reviewed to identify those indicators most closely linked with the provision of river ecosystem services. Finally, we illustrate how our approach can be applied to management through contrasting watershed examples, including a highly modified agricultural region and relatively pristine Arctic watersheds. The proposed approach supports an explicit connection between valued ecosystem services and benthic indicators, providing more targeted assessment results for use in river management decision-making. [ABSTRACT FROM AUTHOR]

Context: In agricultural landscapes, riparian forests are used as a management tool to protect stream ecosystems from agricultural activities. However, the ability of managers to target stream protection actions is limited by incomplete knowledge of scale-specific effects of agriculture in riparian corridor and catchment areas.Objectives: We evaluated scale-specific effects of agricultural cover in riparian corridor and catchment areas on stream benthic macroinvertebrate (BMI) communities to develop cover targets for agricultural landscapes.Methods: Sixty-eight streams assigned to three experimental treatments (Forested Riparian, Agricultural Riparian, Agricultural Catchment) were sampled for BMIs. Ordination and segmented regression were used to assess impacts of agriculture on BMI communities and detect thresholds for BMI community metrics.Results: BMI communities were not associated with catchment agricultural cover where the riparian corridor was forested, but were associated with variation in catchment agriculture where riparian forests had been converted to agriculture. Trait-based metrics showed threshold responses at greater than 70% agricultural cover in the catchment. Increasing agriculture in the riparian corridor was associated with less diverse and more tolerant BMI communities. Eight metrics exhibited threshold responses ranging from 45 to 75% agriculture in the riparian corridor.Conclusions: Riparian forest effectively buffered streams from agricultural activity even where catchment agriculture exceeds 80%. We recommend managers prioritize protection of forested riparian corridors and that restore riparian corridors where agricultural cover is near identified thresholds be a secondary priority. Adoption of catchment management actions should be effective where the riparian corridor has been converted to agriculture. [ABSTRACT FROM AUTHOR]

Expansion and intensification of human land uses has resulted in the loss of all but remnant areas of natural cover over increasingly vast areas of land. Effective stream assessment in these regions thus requires indicators sensitive to ecosystem change in systems that are already highly stressed. The goal of this study was to determine if benthic macroinvertebrate communities in streams exposed to extensive anthropogenic stress are associated with land-use variables and demonstrate potential to be used as bioindicators for assessment of further land use modification. Using the Grand River in southern Ontario as our model, we sampled for benthic macroinvertebrates in 70 small (3–20 km 2 ) sub-watersheds that comprised a gradient of intensive land use (65–100% developed). Redundancy analysis and variance partitioning results indicated that macroinvertebrate taxonomy and traits were only weakly associated with environmental gradients with the strongest associations occurring at the reach scale. With strong anthropogenic filters present across the watershed, it is likely that the majority of benthic macroinvertebrate communities in the Grand River have experienced a homogenization towards tolerant taxa and traits that respond more to local habitat variables. Threshold Indicator Taxa Analysis (TITAN) revealed 19 valid taxa indicators and 32 valid trait indicators for one or more of six environmental variables (percent sub-watershed agriculture, percent buffer agriculture, pool substrate, sediment reduction, natural channel, and riparian width). However, individual taxon and community change points exhibited broad quantile scores indicating a gradual or random response to environmental variables. Comparison of traits and taxonomic associations with environmental variables showed minimal difference suggesting traits may not offer increased sensitivity to land-use stress. However, several traits did show potential to serve as diagnostic indicators for specific stressors associated with agricultural land use. Our ability to identify even a few indicators in a region with intensive human activity is promising for land managers charged with detecting biotic alterations in this stressed system. Further research developing indicators sensitive to intensification of anthropogenic stress in extensively developed landscapes is critical to ensuring managers have the tools needed to protect and enhance aquatic resources. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Water Resources Journal / Revue Canadienne des Ressources Hydriques is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Temporal variation may influence the ability of best management practices (BMPs) to mitigate the loss of agricultural pollutants to streams. Our goal was to assess variation in mitigation effects of BMPs by examining the associations between instream nutrient concentrations and the abundance and location of four structural BMPs over a hydrologic year. Water samples were collected monthly (Nov. 2013–Oct. 2014) in 15 headwater streams representing a gradient of BMP use in Southern Ontario, Canada. Partial least squares (PLS) regression models were used to associate two groups of collinear nutrient forms with the abundance and location of BMPs, antecedent precipitation and time of year. BMP metrics in PLS models were associated with instream concentrations of major phosphorus forms and ammonium throughout the year. In contrast, total nitrogen and nitrate-nitrite were only associated with BMPs during snowmelt. BMP metrics associated with reductions of phosphorus and ammonium included greater abundances of riparian buffers and manure storage structures, but not livestock restriction fences. Likewise, the abundance and location riparian vegetation in areas capturing more surface runoff were associated with decreased stream nitrogen concentrations during snowmelt. However, the amount of tile drainage was associated with increased nitrogen concentrations following snowmelt, as well as with greater phosphorus and ammonium concentrations throughout the year. Overall, our findings indicate that increasing the abundance of riparian buffers and manure storage structures may decrease instream nutrient concentrations in agricultural areas. Additionally, the implementation of these structural BMPs appear to be an effective year-round strategy to assist management objectives in reducing phosphorus concentrations in small agricultural streams and thus loadings to downstream tributaries. Further mitigation measures, such as managerial BMPs and controlled tile drainage, may be required to further reduce instream nutrient concentrations during baseflow periods and snowmelt events. [ABSTRACT FROM AUTHOR]

Best management practices (BMPs) are tools commonly used to mitigate negative impacts of agriculture on water quality; however, the relationship between BMPs and aquatic ecological function is unknown. Our research goal was to determine the association between both stream ecosystem metabolism and water quality, and the abundance and location of four different BMPs in agricultural catchments. Dissolved oxygen was measured over a two-week period in mid-June and used to estimate ecosystem metabolism of 13 headwater streams representing a gradient of BMP implementation in Southern Ontario, Canada. Stepwise regression analyses were used to associate stream metabolism and water quality with metrics describing the abundance and location of BMPs within each catchment. Studied streams exhibited rates of metabolism comparable to catchments from other agricultural regions. However, metrics of BMP implementation were not associated with either stream metabolism or water quality. Our results suggest that BMPs in the studied agricultural catchments are not improving water quality or mitigating water quality impacts on stream metabolism during the summer season. We propose that seasonality of catchment hydrology and time lag effects associated with past agricultural land use may be masking the mitigation benefits of BMPs on stream ecosystem conditions during the summer season. [ABSTRACT FROM AUTHOR]

Few researchers have assessed the important management questions regarding the sensitivity of indicators of aquatic ecosystem condition and the specificity with which anthropogenic development activities are described. Furthermore, there is limited knowledge as to the potential of structural and functional indicators to generate complementary knowledge about ecological condition that can be used to inform watershed management. We assessed 20 metrics of ecological structure and function at 19 riverine sites across the Red River watershed in the summer of 2010 using a gradient approach to test predictions that: (1) indicator sensitivity would vary with the specificity at which landscape development is described (i.e., coarse - land use [e.g., agriculture], medium - specific human activities [e.g., crop cultivation] and fine - management practices [e.g., crop rotation]); and (2) structural and functional indicators respond to different types and specificity of anthropogenic development. Evaluation of indicators revealed that indicator sensitivity was frequently greater for assessment of specific human activities (i.e., wastewater treatment, crop cultivation or livestock production), than for broad land-use categories (i.e., agriculture or urban). Structural and functional indicators were often associated with different types of anthropogenic development suggesting additive rather than redundant assessment information. Structural indicators were almost exclusively associated with crop cultivation and agricultural land cover. In contrast, functional indicators were generally associated with gradients of wastewater treatment and urban land cover. Our results demonstrate that aquatic ecosystem assessment programs would benefit from considering the specific anthropogenic development activity to be assessed and managed in order to evaluate and select the most sensitive indicators of stream condition. Furthermore, combined use of structural and functional indicators in aquatic monitoring program appears to improve detection of anthropogenic impacts in a multiple stressor environment. [ABSTRACT FROM AUTHOR]

Small watersheds in the Canadian Prairies are characterized by seasonally disconnected hydrologic networks whereby stream channels are hydrologically connected during snowmelt but have disconnected reaches throughout the remainder of the year. Snowmelt is the most significant hydrological event in the Canadian Prairies, yet few studies have investigated the role of snowmelt in the nutrient budget of prairie streams. We quantified hydrologic and nutrient dynamics during snowmelt for ten agricultural subwatersheds distributed along a gradient of human activity in the Red River Valley, Canada, to evaluate the timing of nitrogen (N) and phosphorus (P) export. Elevated concentrations of total P (TP) and total N (TN) were observed during the snowmelt peak, with maximum concentrations reaching 3.23 mg TP L-1 and 18.50 mg TN L-1. Dissolved P and N dominated the total nutrient pool throughout snowmelt, likely due to reduced erosion and sediment transport resulting from the combination of the flat topography, frozen soil and stream banks, and gradual snow cover melt. Significant correlations were observed between snowmelt N load (r = 0.91; p < 0.05) and both agricultural land cover and fertilizer usage, with a weaker correlation between snowmelt P load (r = 0.81; p < 0.05) and agricultural area. Our results showed that snowmelt plays a key role in nutrient export to prairie aquatic ecosystems and this may have serious impacts on downstream ecosystems. Land use management practices need to consider the snowmelt period to control nutrient loads to Lake Winnipeg and other waterbodies in the Great Plains. [ABSTRACT FROM AUTHOR]

Abstract: Using human activity and stream biota data collected from 160 small (600–3000ha) watersheds in rural southwestern Ontario, we determined the relative ability of three commonly used methods of describing fish and benthic macroinvertebrate assemblages (i.e., metrics, presence/absence, and relative abundance) to assess the biological effects of reach and basin scale human activity. Analyses indicated that benthic macroinvertebrate presence/absence was more strongly correlated with human activity at both reach and basin scales than fish presence/absence, benthic macroinvertebrate or fish relative abundance, and metrics derived from benthic macroinvertebrates or fish data. However, sites exhibiting lower levels of human activity were, in some cases, better differentiated by relative abundance. The use of metrics did not provide any additional information regarding the effects of human activities and regularly appeared to underestimate differences between moderately exposed sites and sites exposed to low or very high levels of human activity. Tests for redundancy between fish and benthic macroinvertebrates indicated that they respond differently to the same type and extent of human activity suggesting that the assemblages are sensitive to different stressors emanating from the same activities. There was also a disparity between assemblages with regards to which scale they were most strongly associated as fish were more associated with human activities at the basin scale whereas benthic invertebrates were most strongly associated with the activities at the reach scale. Finally, there was no apparent advantage to describing human activities at multiple scales as predicted basin scores were highly correlated among scales, a finding that may be attributable to the homogeneity of rural environments. Similar studies need to be conducted for a broader spectrum of human activities across a larger geographic extent to determine if these findings are widely applicable. [Copyright &y& Elsevier]

The linkage of trait responses to stressor gradients has potential to expand biomonitoring approaches beyond traditional taxonomically based assessments that identify ecological effect to provide a causal diagnosis. Traits-based information may have several advantages over taxonomically based methods. These include providing mechanistic linkages of biotic responses to environmental conditions, consistent descriptors or metrics across broad spatial scales, more seasonal stability compared with taxonomic measures, and seamless integration of traits-based analysis into assessment programs. A traits-based biomonitoring approach does not require a new biomonitoring framework, because contemporary biomonitoring programs gather the basic site-by-species composition matrices required to link community data to the traits database. Impediments to the adoption of traits-based biomonitoring relate to the availability, consistency, and applicability of existing trait data. For example, traits generalizations among taxa across biogeographical regions are rare, and no consensus exists relative to the required taxonomic resolution and methodology for traits assessment. Similarly, we must determine if traits form suites that are related to particular stressor effects, and whether significant variation of traits occurs among allopatric populations. Finally, to realize the potential of traits-based approaches in biomonitoring, a concerted effort to standardize terminology is required, along with the establishment of protocols to ease the sharing and merging of broad, geographical trait information. Integr Environ Assess Manag 2011;7:187-197. © 2010 SETAC [ABSTRACT FROM AUTHOR]

1. Bioassessment has evolved significantly from a method of deciding whether an ecosystem exposed to stressors should ‘pass’ or ‘fail’ (or how badly it fails). Society wants some notion of what has caused any observed degradation of ecosystems, and what management strategies might improve degraded ecosystems. Managers also want to predict what negative or positive effects different land use strategies will have on the component ecosystems of a landscape, including lakes and streams. 2. Here we illustrate an approach to providing these tools to managers with data from a bioassessment study of streams in the Fraser River Basin of British Columbia, Canada. 3. Landscape scale descriptors of both the natural (e.g. catchment size, surficial geology) and stressor (e.g. hard rock mines, forest harvest) environment of each site were used to define the natural and stressor environments of each of the 242 stream sites. 4. We classified 206 reference (relatively unexposed to human activity) sites using their benthic macroinvertebrate community composition, and then discriminated among the faunally defined groups with landscape scale descriptors of the natural environment of the sites. 5. This discriminant function model allowed us to predict which group each of the test sites would be in if it were in reference condition, and then measure the relationship between the amount of human activity and the biota in each of these groups. 6. These relationships were turned into projections of what will happen to a stream ecosystem's biota if the stressor environment is either improved or degraded. These projection models form the basis of evidence-based land use planning that takes into account the health of freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Bioassessment assumes that ecological conditions remain stable in the absence of environmental changes. Evidence suggests this assumption may hold for reference streams, but knowledge gaps remain for impacted streams. Our study quantified interannual variation of benthic macroinvertebrate communities, monitored for at least 14 years in eight impacted streams in the Upper Thames River watershed in Ontario, Canada. Benthic communities exhibited moderate interannual variation in relative abundance of EPT (Ephemeroptera, Plecoptera and Trichoptera) and Chironomidae taxa. Year-to-year changes were reflected in lower community persistence than that observed in studies of reference streams. In contrast, tolerance-based metrics showed minimal interannual variation, suggesting compositional changes were because of taxonomic substitutions, in which one tolerant taxon replaced another. Analyses indicated limited directionality in temporal variation for most bioassessment metrics. An exception was taxa richness, which increased at most sites, possibly because of changes in subsampling. However, no associations between calculated bioassessment metrics and measured environmental factors (stream flow and water chemistry) or sampling procedures were observed. We conclude interannual variation in ecological conditions can be substantial and may not be associated with deterministic factors routinely measured in stream assessments. We recommend increased sampling frequency and traits-based assessment as options for limiting effects of interannual variation on assessment results. [ABSTRACT FROM AUTHOR]

• Cumulative effects of human activities are widespread in developed regions. • We assessed effects of agriculture and sewage effluent on stream communities. • Macroinvertebrate and diatom assemblage conditions declined with nutrient enrichment. • Enrichment effects were conditional on upstream nutrient status. • Assessment design needs to account for complexities in multi-use catchments. Human impacts on stream ecosystems are expected to intensify with population growth and climate change. Decisive information on how stream communities respond to cumulative human impacts is therefore integral for protecting streams draining multi-use catchments. To determine cumulative influences of nutrient enrichment and assess more nuanced approaches for the evaluation of human impacts, we present results from one factorial and two gradient assessment designs applied to benthic algae and macroinvertebrate data from 14 mid-order streams in southern Ontario, Canada with pre-existing human impacts (i.e., sewage effluent and agriculture). We found that among stream variability in ecological indicators measured downstream of sewage effluent outfalls confounded our generalized factorial assessment and provided inconclusive information on a known human impact. Despite our gradient assessment also not having strong statistical support, accounting for the extent of nutrient enrichment associated with differences in sewage effluent and agricultural inputs revealed that larger longitudinal changes in stream communities were associated with increased nutrient enrichment. However, re-weighting our nutrient enrichment gradient based on upstream nutrient concentrations to account for nonlinearities in the response of stream communities to nutrient enrichment produced more robust assessment results that were consistent with predicted effects of nutrients on stream ecosystems. Thus, while our factorial assessment suggests that the communities are resistant to nutrients from cumulative human impacts, our targeted gradient assessment demonstrates that the effects of nutrient enrichment are highly conditional on upstream ecosystem conditions. Future assessments may need to go beyond traditional approaches (i.e., impact presence/absence) and more explicitly consider the environmental stressors and their associated complexities related to the impact under investigation. [ABSTRACT FROM AUTHOR]

Intensive agriculture and growing human populations are important nitrogen (N) sources thought to be associated with eutrophication. However, the contribution and seasonality of N delivery to streams from human activities is poorly understood and knowledge of the role of stream communities in the assimilation of N from human activities is limited. We used N and oxygen stable isotope ratios of dissolved inorganic N (DIN) and concentrations of artificial sweeteners to identify the relative contribution of key sources of anthropogenic N (i.e., fertilizers, human, and livestock waste) to tributaries of the Red River Valley (RRV), Manitoba, Canada. Water and algae were sampled in 14 RRV tributaries during snowmelt, spring, summer, and autumn; and water was sampled at three locations in the Red River in spring, summer, and autumn. δ15N values of DIN in tributary water differed seasonally and were greatest during snowmelt. Incorporation of ammonium δ15N provided evidence for the importance of manure N to tributaries during snowmelt. Fertilizer and municipal lagoons served as principal sources of N to streams in spring and summer. Human and livestock waste sources of N were the dominant contributor to algae at greater than 90% of sites and algae δ15N was greatest at sites downstream of municipal lagoons. We also showed that the tributaries contribute human and livestock waste N to the Red River, though much of the nitrate in the river originates outside of Manitoba. Overall, our study determined that the anthropogenic sources of N to RRV streams vary seasonally, likely due to regional hydrologic conditions. Our study also showed the potential of artificial sweeteners and ammonium δ15N as tools for identifying N sources to rivers. Moreover, we demonstrate the need for the management of N sources and the protection of stream function to control downstream transfer of N from landscapes to waterbodies. Unlabelled Image • Contribution and timing of delivery of nitrogen to streams is poorly understood. • N sources identified using stable isotopes varied seasonally. • Use of artificial sweeteners aided differentiation of human and livestock waste. • Livestock N was dominant in snowmelt and sewage lagoons were important in summer. • Evidence of transport of waste sources of N from tributaries to the Red River [ABSTRACT FROM AUTHOR]

Environmental metabolomics has been proposed as a tool for biomonitoring because organisms regulate production or consumption of metabolites in response to environmental conditions. We evaluated the efficacy of the metabolome of three tissues (hepatopancreas, gill, and tail muscle) from the northern crayfish (Faxonius virilis) to detect and differentiate between impacts of human activities (i.e., reference, municipal wastewater, and agriculture). We conducted a reciprocal transfer study exposing crayfish for 1 or 2 weeks in three streams with different amounts and types of human activities in southern Manitoba, Canada. Tissue samples were analyzed using nuclear magnetic resonance spectroscopy to generate a metabolic profile. Findings indicated the gill tissue metabolome best detected and differentiated between human activities. In particular, the gill metabolome was able to rapidly integrate abrupt changes in environmental conditions associated with municipal wastewater activity. In contrast, the tail metabolome best differentiated between crayfish collected at the reference site from those collected at the two impacted sites. Metabolites extracted from hepatopancreas tissue showed limited and inconsistent detection of among site differences. Based on our findings, we conclude that the metabolome of the northern crayfish can be an effective biomonitoring tool, but monitoring purpose will dictate tissue selection. Indeed, we recommend the gill metabolome be used for short-term assays aimed at detecting acute effects, whereas the tail be applied for survey monitoring aimed at detecting deviations in ecological condition at test sites from reference site conditions. Unlabelled Image • Crayfish (Faxonius virilis) metabolome was tested as an aquatic bioindicator. • Metabolic response to human activity was tissue dependent. • Metabolome distinguished between reference, sewage and/or agricultural activities. • Metabolome has promise for assessing acute and chronic exposure to human activity. [ABSTRACT FROM AUTHOR]

The oil sands region in northeastern Alberta, Canada contain approximately 165 billion barrels of oil making it the third largest oil reserves in the world. However, processing of extracted bitumen generates vast amounts of toxic byproduct known as oil sands process waters. Naphthenic acids and associated sodium naphthenate salts are considered the primary toxic component of oil sands process waters. Although a significant body of work has been conducted on naphthenic acid toxicity at levels comparable to what is observed in current oil sands process waters, it is also important to understand any impacts of exposure to sublethal concentrations. We conducted a microcosm study using the mayfly Hexagenia spp . to identify sublethal impacts of naphthenic acid exposure on the survival, growth, and metabolome across a concentration gradient (0-100 μg L -1 ) of sodium naphthenate. Nuclear magnetic resonance-based metabolomic analyses were completed on both the polar and lipophilic extracted fractions of whole organism tissue. We observed a positive relationship between sodium naphthenate concentration and mean principal component score of the first axis of the polar metabolome indicating a shift in the metabolome with increasing naphthenic acid exposure. Eleven metabolites correlated with increased naphthenic acid concentration and included those involved in energy metabolism and apoptosis regulation. Survival and growth were both high and did not differ among concentrations, with the exception of a slight increase in mortality observed at the highest concentration. Although lethal concentrations of naphthenic acids in other studies are higher (150-56,200 μg L -1 ), our findings suggest that physiological changes in aquatic invertebrates may begin at substantially lower concentrations. These results have important implications for the release of naphthenic acids into surface waters in the Alberta oil sands region as an addition of even small volumes of oil sands process waters could initiate chronic effects in aquatic organisms. Results of this research will assist in the determination of appropriate discharge thresholds should oil sands process waters be considered for environmental release., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Pomfret, Brua, Milani and Yates.)

The biological assessment of rivers i.e., their assessment through use of aquatic assemblages, integrates the effects of multiple-stressors on these systems over time and is essential to evaluate ecosystem condition and establish recovery measures. It has been undertaken in many countries since the 1990s, but not globally. And where national or multi-national monitoring networks have gathered large amounts of data, the poor water body classifications have not necessarily resulted in the rehabilitation of rivers. Thus, here we aimed to identify major gaps in the biological assessment and rehabilitation of rivers worldwide by focusing on the best examples in Asia, Europe, Oceania, and North, Central, and South America. Our study showed that it is not possible so far to draw a world map of the ecological quality of rivers. Biological assessment of rivers and streams is only implemented officially nation-wide and regularly in the European Union, Japan, Republic of Korea, South Africa, and the USA. In Australia, Canada, China, New Zealand, and Singapore it has been implemented officially at the state/province level (in some cases using common protocols) or in major catchments or even only once at the national level to define reference conditions (Australia). In other cases, biological monitoring is driven by a specific problem, impact assessments, water licenses, or the need to rehabilitate a river or a river section (as in Brazil, South Korea, China, Canada, Japan, Australia). In some countries monitoring programs have only been explored by research teams mostly at the catchment or local level (e.g., Brazil, Mexico, Chile, China, India, Malaysia, Thailand, Vietnam) or implemented by citizen science groups (e.g., Southern Africa, Gambia, East Africa, Australia, Brazil, Canada). The existing large-extent assessments show a striking loss of biodiversity in the last 2-3 decades in Japanese and New Zealand rivers (e.g., 42% and 70% of fish species threatened or endangered, respectively). A poor condition (below Good condition) exists in 25% of South Korean rivers, half of the European water bodies, and 44% of USA rivers, while in Australia 30% of the reaches sampled were significantly impaired in 2006. Regarding river rehabilitation, the greatest implementation has occurred in North America, Australia, Northern Europe, Japan, Singapore, and the Republic of Korea. Most rehabilitation measures have been related to improving water quality and river connectivity for fish or the improvement of riparian vegetation. The limited extent of most rehabilitation measures (i.e., not considering the entire catchment) often constrains the improvement of biological condition. Yet, many rehabilitation projects also lack pre-and/or post-monitoring of ecological condition, which prevents assessing the success and shortcomings of the recovery measures. Economic constraints are the most cited limitation for implementing monitoring programs and rehabilitation actions, followed by technical limitations, limited knowledge of the fauna and flora and their life-history traits (especially in Africa, South America and Mexico), and poor awareness by decision-makers. On the other hand, citizen involvement is recognized as key to the success and sustainability of rehabilitation projects. Thus, establishing rehabilitation needs, defining clear goals, tracking progress towards achieving them, and involving local populations and stakeholders are key recommendations for rehabilitation projects (Table 1). Large-extent and long-term monitoring programs are also essential to provide a realistic overview of the condition of rivers worldwide. Soon, the use of DNA biological samples and eDNA to investigate aquatic diversity could contribute to reducing costs and thus increase monitoring efforts and a more complete assessment of biodiversity. Finally, we propose developing transcontinental teams to elaborate and improve technical guidelines for implementing biological monitoring programs and river rehabilitation and establishing common financial and technical frameworks for managing international catchments. We also recommend providing such expert teams through the United Nations Environment Program to aid the extension of biomonitoring, bioassessment, and river rehabilitation knowledge globally., Competing Interests: Conflicts of Interest: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. This manuscript was reviewed by the USEPA Center for Public Health and Environmental Assessment’s Pacific Ecological Systems Division and approved for publication. Approval does not signify that the contents reflect the views of the USEPA, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth's biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented "next-generation biomonitoring" by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.