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The aim of this study was to test the effects of agricultural land use on benthic insect population body-mass and community biomass size spectrum. Agricultural land use effects were assessed by conducting a reciprocal transfer experiment between two stream reaches exposed to differing intensities of row crop and livestock agricultural activity representing best attainable and highly developed agricultural land use scenarios. We found that transferred insect communities showed no change in richness, abundance, distribution or biomass, indicating that exposure to increased agricultural intensity did not have selective lethal effects on transferred benthic insect communities. However, populations of Ephemerellidae and Hydropsyche demonstrated an increase and decrease, respectively, in body-mass following the transfer to the best attainable agriculture site. Furthermore, the community biomass size spectrum at the best attainable agriculture site contained large, predatory insects not found at the intensive agriculture site. Our findings suggest that taxon-specific body-mass and biomass size spectra have the potential to detect environmental effects prior to long-term community changes. Further research is needed to explore the mechanisms by which changes in the biomass size spectrum link agricultural intensity to shifts in benthic insect community structure. [ABSTRACT FROM AUTHOR]

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]

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]

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. [ABSTRACT FROM AUTHOR]

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]

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]

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]

Bioassessment is based upon the premise that biological assemblages have predictable relationships with the surrounding natural and human environments. As the nature of these relationships can vary from region to region, it is important that environment–biota relationships be established prior to the initiation of any bioassessment program. In this study, multivariate analysis was used to establish how fish and benthic macroinvertebrate (BMI) assemblages in southwestern Ontario streams vary across natural and human activity gradients. The use of canonical correspondence analysis allowed us to determine that changes in community composition of both fish and BMI are strongly correlated with variation in the extent of human activity. The primary source of variation in community composition across activity gradients appeared to reflect a shift from intolerant to tolerant taxa as the extent of human activity increased. Habitat and feeding traits, for BMI and fish respectively, accounted for a secondary source of variation primarily attributable to differences in the extent of human activity at the reach scale. However, variation in human activity, especially at the basin scale, covaried with the dominant natural gradient of surface geology, making interpretation of the results difficult. Implications for bioassessment studies are discussed. [ABSTRACT FROM AUTHOR]

Aim The aim of this study was to understand the roles of landscape features in shaping patterns of contemporary and historical genetic diversification among populations of the Andean tree frog ( Hypsiboas andinus) across spatial scales. Location Andes mountains, north-western Argentina, South America. Methods Mitochondrial DNA control region sequences were utilized to assess genetic differentiation among populations and calculate population pair-wise genetic distances. Three models of movement, namely traditional straight-line distance and two effective distances based on habitat classification, were examined to determine which of these explained the most variation in pair-wise population genetic differentiation. The two habitat classifications were based on digital vegetation and hydrology layers that were generated from a 90-m resolution digital elevation model (DEM) and known relationships between elevation and habitat. Mantel tests were conducted to test for correlations between geographic and genetic distance matrices and to estimate the percentage variation explained by each type of geographic distance. To investigate the location of possible barriers to gene flow, we used Monmonier’s maximum difference algorithm as implemented inbarrier 2.2. Results At both geographic scales, effective distances explained more variation in genetic differentiation than did straight-line distance. The least-cost distances based on the simple classification performed better than the more detailed habitat classification. We controlled for the effects of historical range fragmentation determined from previous nested clade analyses, and therefore evaluated the effect of different distances on the genetic variation attributable to more recent factors. Effective distances identified populations that were highly divergent as a result of isolation in unsuitable habitats. The proposed locations of barriers to gene flow identified using Monmonier’s maximum difference algorithm corresponded well with earlier analyses and supported findings from our partial Mantel tests. Main conclusions Our results indicate that landscape features have been important in both historical and contemporary genetic structuring of populations of H. andinus at both large and small spatial scales. A landscape genetic perspective offers novel insights not provided by traditional phylogeographic studies: (1) effective distances can better explain patterns of differentiation in populations, especially in heterogeneous landscapes where barriers to dispersal may be common; and (2) least-cost path analysis can help to identify corridors of movement between populations that are biologically more realistic. [ABSTRACT FROM AUTHOR]

Knowledge of benthic macroinvertebrate β-diversity patterns and drivers in an agricultural landscape can inform and improve watershed management decisions. Our study used multi-site and pairwise measures to determine taxonomic and functional β-diversity and associated nestedness and turnover components for benthic macroinvertebrate communities in the agricultural landscape. Total taxonomic β-diversity was mostly due to turnover, whereas total functional β-diversity was composed of turnover and nestedness more equally. Variation partitioning showed that spatial and habitat variables explained the largest proportion of variation in the total and turnover component of both taxonomic and functional β-diversity. Variation in nestedness was associated with local-scale habitat. Agricultural land cover was not a driver of β-diversity; however, extensive agricultural land cover appeared to disrupt the habitat–functional β-diversity relationship. Our findings suggest that distance among benthic macroinvertebrate communities should be considered when making land management or conservation decisions. Moreover, apparent disruption of the habitat–functional β-diversity relationship with extensive agricultural cover suggests managers should strategically target restoration activities to upland or channel areas based on catchment conditions. Finally, differences between taxonomic and functional β-diversity suggest including both measures in monitoring programs may enhance regional biodiversity assessments. [ABSTRACT FROM AUTHOR]

• SRP dynamics in streambed sediments are complex and heterogeneous over small scales. • SRP concentrations closely linked to iron and possibly manganese redox cycling. • High porewater SRP close to streambed surface likely derived from P-rich sediments. • Oxic cap may limit SRP flux to stream but is temporally and spatially discontinuous. Streambed sediment and groundwater represent important stores of soluble reactive phosphorus (SRP) in freshwater catchments yet their contributions to watershed SRP loads remain unclear. This study evaluates the spatio-temporal variability and geochemical and hydrologic controls on porewater SRP in the streambed along an agricultural reach, including the influence of groundwater-surface water interactions. High porewater SRP (>1000 µg/L) and high available sediment-bound SRP were observed in low groundwater discharge zones, specifically in the shallow (≤0.1 m) streambed sediments. Porewater SRP concentrations were linked to iron and possibly manganese redox cycling with more-reducing conditions consistently coinciding with high SRP. Porewater SRP varied temporally but distinct seasonal changes across the stream reach were not observed. A shallow oxic cap that may limit SRP release to the stream was observed in the very shallow streambed but its presence was spatially and temporally discontinuous. Finally, data indicate P-rich shallow streambed sediments are the likely source of the observed high SRP porewater concentrations in the streambed rather than incoming groundwater from the adjacent fields. Overall, the findings highlight the complexity of SRP dynamics in agricultural streambeds and provide insight into processes governing the timing and location of SRP loading streams. [ABSTRACT FROM AUTHOR]

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]

It has been proposed that biomonitoring may benefit from the use of metabolomics (the study of all small molecules in an organism) to detect sub-lethal organism stress through changes in the metabolite profile (i.e., the metabolome). However, to integrate the metabolome into biomonitoring programs the amount of natural variability among and within populations of indicator taxa must be established prior to generating a reference condition. This study determined variation in the metabolome among ecoregion and stream of origin in the northern crayfish (Faxonius virilis) and if that variation inhibited detection of stressor effects at sites exposed to human activities. We collected crayfish from seven minimally disturbed streams (i.e., reference streams), distributed across three level II ecoregions in central Canada and compared their metabolomes. We found ecoregion and stream origin were poor predictors of crayfish metabolomes. This result suggests crayfish metabolomes were similar, despite differing environmental conditions. Metabolomes of crayfish collected from three stream sites exposed to agricultural activity and municipal wastewater (i.e., test sites) were then compared to the crayfish metabolomes from the seven reference streams. Findings showed that crayfish metabolomes from test sites were strongly differentiated from those at all reference sites. The consistency in the northern crayfish metabolome at the studied reference streams indicates that a single reference condition may effectively detect impacts of human activities across the sampled ecoregions. • Application of metabolomics may enhance bioassessment of ecosystems. • Crayfish metabolomes from reference streams did not differ among ecoregion or stream. • Natural variation did not impede detection of impacts of human activity. • Regional reference conditions could include streams from multiple ecoregions. [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]

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]

Light, temperature, and discharge control stream metabolism, but the response of gross primary production (GPP) and ecosystem respiration (ER) to seasonal variation in these physical drivers may differ in accordance with the types of human activities present in the catchment. Our study examined three mid-order streams in southern Ontario, Canada that differed in anthropogenic nutrient sources (i.e., sewage treatment plant effluent, sewage lagoon effluent, and agriculture), but had comparable light, temperature, and discharge regimes. For each stream, GPP and ER were estimated daily from June through November. Comparisons of paired daily metabolic rates revealed pairwise differences among all streams, with streams receiving sewage effluent having greater rates and variability of GPP and ER than the stream draining agricultural land. The two sewage influenced streams differed only in ER. Temporal patterns of GPP and ER were correlated for all streams throughout the study period and were most affected by seasonal variation in temperature, whereby effluent receiving streams responded more rapidly to increases in temperature. Our findings suggest that managers may need to balance effects of human activities with regional environmental constraints on stream metabolism to maintain and enhance the ecological condition and services of stream ecosystems. [ABSTRACT FROM AUTHOR]

Global degradation of aquatic ecosystems has initiated widespread use of biomonitoring to inform management. Current biomonitoring programs typically apply biomarkers (e.g., vitellogenin) and (or) measurements of community composition (e.g., algae or benthic macroinvertebrates) as indicators to assess ecosystem condition. However, independently these indicators may fail to provide either ecologically significant (a limitation of biomarkers) or early warning (a limitation of population and community measures) information to aquatic managers. Environmental metabolomics studies the relationship between an organism's environment and its metabolome (i.e., description of the state of molecules produced or consumed during an organism's metabolic processes, e.g., amino acids). Shifts in the metabolome occur because of stress-driven changes in resource allocation and are often indicative of changes in organism fitness. The metabolome of target species may thus be an effective bioindicator; however, it has not been evaluated for use in aquatic biomonitoring. Our objectives were threefold: introduce and describe metabolomics, evaluate the metabolome as a bioindicator, and provide recommendations for integration of metabolomics into biomonitoring. We conclude that the metabolome meets many bioindicator criteria and the potential to meet the remaining criteria following further research. Specifically, we concluded the metabolome is grounded in sound ecological theory while also having the potential to be a priori predictive and to assess ecological functions. Although the reliability of the metabolome to detect change needs further study, there is growing evidence that the metabolome can detect changes in human impact and discriminate between stressors. We provide an example of this capability with a case study assessment of municipal wastewater. Practically, the metabolome can be readily integrated into existing biomonitoring protocols. However, the ability of agencies to adopt metabolomics-based biomonitoring may be impeded by a lack of understanding of metabolomics within institutions and difficulty of communication with stakeholders. We suggest training or hiring of appropriate personnel and the generation of a common metabolomics language as mechanisms for overcoming this impediment. We conclude that background knowledge for metabolomics-based monitoring is sufficient for agency-based pilot projects aimed at assessing ecological status of aquatic ecosystems. However, continued development may ultimately provide early warning and diagnostic assessments of aquatic impacts. [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]

Phosphorus (P) is an essential macronutrient for algal communities, but in excess can exacerbate stream eutrophication. However, P loadings to streams vary temporally from continuous to episodic as a result of inputs from point and non-point sources, respectively. P loading pattern can thus alter the temporal availability of P and may influence effects of P enrichment on algal communities. We assessed how P loading pattern influences algal biomass and composition by conducting a 29-day P enrichment experiment in nine artificial streams exposed to either: (1) continuous P enrichment; (2) episodic P enrichment, or; (3) no P enrichment. P enrichment increased algal biomass accrual, but peak biomass did not differ between continuously and episodically enriched treatments. Maximum absolute growth rates were also comparable between P enriched treatments. However, episodic P additions sustained elevated rates of biomass accrual, whereas absolute growth rates in the continuously enriched communities declined towards the end of the experiment. P enrichment resulted in comparable increases in relative abundance of chlorophytes and decreased proportions of bacillariophytes and charophytes in algal communities for continuously and episodically enriched treatments. However, composition of bacillariophyte (diatom) assemblages differed significantly among all P enrichment treatments in accordance with species autecological attributes for P. Our results demonstrate that episodic and continuous P enrichment may augment algal biomass similarly. Yet, P loading pattern regulated the composition of algal communities. Thus, remedial management strategies for the control of nuisance algae production may require focus on the predominant source of P to streams. Finally, species specific responses of diatom assemblages to P enrichment and associated loading patterns suggests this taxonomic group may have potential as diagnostic indicators for identifying the presence of key nutrient sources associated with eutrophication of stream ecosystems. Image 1 • Temporal patterns of phosphorus delivery may influence benthic algae communities. • Artificial streams simulated continuous and episodic phosphorus enrichment. • Phosphorus delivery pattern altered species composition but not biomass. • Short-duration phosphorus pulses can structure stream algal communities. • Stream management may benefit by addressing episodic phosphorus enrichment. [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]