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The boreal forest is one of the world's largest terrestrial biome and plays crucial roles in global biogeochemical cycles, such as carbon (C) sequestration in vegetation and soil. However, the impacts of decades of N deposition on N-limited ecosystems, like the eastern Canadian boreal forest, remain unclear. For 13 years, N deposition was simulated by periodically adding ammonium nitrate on soils of two boreal coniferous forests (i.e., balsam fir and black spruce) of eastern Canada, at low (LN) and high (HN) rates, corresponding to 3 and 10 times the ambient N deposition, respectively. We show that more than a decade of N addition had no strong effects on mineral soil C, N, P, and cation concentrations and on foliar total Ca, K, Mg, and Mn concentrations. In organic soil, C stock was not affected by N addition while N stock increased, and exchangeable Ca 2+ and Mg 2+ decreased at the balsam fir site under HN treatment. At both sites, LN treatment had nearly no impact on foliage and soil chemistry but foliar N and N:P significantly increased under HN treatment, potentially leading to foliar nutrient imbalance. Overall, our work indicates that, in the eastern Canadian boreal forest, soil and foliar nutrient concentrations and stocks are resilient to increasing N deposition potentially because, in the context of N limitation, extra N would be rapidly immobilized by soil micro-organisms and vegetation. These findings could improve modeling future boreal forest soil C stocks and biomass growth and could help in planning forest management strategies in eastern Canada., (© 2024 The Ecological Society of America.)

This study conducted a spatio-temporal analysis of runoff, total suspended sediment, suspended particulate carbon, nitrogen, and phosphorus loadings within the 2.06 km 2 Steppler subwatershed in southern Manitoba of Canada based on 11 years of field monitoring data collected at nine stations. Results showed that the nutrient losses were very small because of the implementation of multiple BMPs in the study area. However, a high spatio-temporal variation of runoff and water quality parameters was found for the nine fields within the subwatershed. The average runoff coefficient was 0.19 at the subwatershed outlet with sediment, suspended particulate carbon, total nitrogen, and total phosphorus losses of 73.8, 6.10, 4.54, and 0.76 kg/ha respectively. Spring snowmelt runoff was about 74.5% of the annual runoff at the subwatershed outlet, while for sediment, suspended particulate carbon, total nitrogen, and total phosphorus, the proportions were 61.1%, 63.6%, 74.9%, and 81.2% respectively during the monitoring period, which suggests that BMPs designed for reducing nutrient loadings from snowmelt runoff would be more effective than BMPs designed for reducing pollutant loading from rainfall storms in the study area. Research findings from this study will benefit the enhancement of current BMPs and the development of new BMPs in the region to minimize soil and nutrient losses from agricultural fields and improve water quality in receiving water bodies., (© 2023. Crown.)

Canada's livestock production and human populations are concentrated in southern regions. Understanding spatial and temporal distributions of animals and excreted nutrients is key to optimizing manure resources and minimizing impact of livestock. Here, we identify manureshed concerns and opportunities by reconciling nitrogen supply and demand on a regional and national scale. Data based on national statistics and farm surveys were allocated to homogeneous soil polygons (Soil Landscapes of Canada [SLC]) to quantify changes in nutrient distribution and ammonia (NH 3 ) emissions across Canada (1981-2018). Livestock sectors tied to domestic consumption, dairy and poultry, were stable over time and well dispersed. Export driven beef production has moved west since 1981, whereas pig production was prominent in Manitoba, Quebec, and Ontario. Per ha manure N excretion across livestock sectors in 2018 was generally low with 58% and 6% of the SLCs averaging <25 and >100 kg N ha -1 , respectively. Although only 3% of SLCs had average NH 3 emissions reaching 16-200 kg ha -1 , most of these were located near cities and emissions spiked in spring when more people might be exposed. The greatest concentrations of nutrients and livestock occurred around the three largest metropolitan areas: Toronto, Montreal-Quebec City, and Vancouver, posing challenges for nutrient recycling and public health. This study shows that as Canadian cities and livestock agriculture grow in southern Canada, so will challenges around food production, human health, and managing nutrients. Livestock and land use strategies are needed to reconcile changing animal sectors and growing populations., (© 2023 His Majesty the King in Right of Canada. Journal of Environmental Quality © 2023 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.)

Edge effects resulting from adjacent land uses are poorly understood in agroecosystems yet understanding above and belowground edge effects is crucial for maintaining ecosystem function. The aim of our study was to examine impacts of land management on aboveground and belowground edge effects, measured by changes in plant community, soil properties, and soil microbial communities across agroecosystem edges. We measured plant composition and biomass, soil properties (total carbon, total nitrogen, pH, nitrate, and ammonium), and soil fungal and bacterial community composition across perennial grassland-annual cropland edges. Edge effects due to land management were detected both aboveground and belowground. The plant community at the edge was distinct from the adjacent land uses, where annual, non-native, plant species were abundant. Soil total nitrogen and carbon significantly decreased across the edge (P < 0.001), with the highest values in the perennial grasslands. Both bacterial and fungal communities were different across the edge with clear changes in fungal communities driven directly and indirectly by land management. A higher abundance of pathogens in the more heavily managed land uses (i.e. crop and edge) was detected. Changes in plant community composition, along with soil carbon and nitrogen also influenced the soil fungal community across these agroecosystems edges. Characterizing edge effects in agroecosystem, especially those associated with soil microbial communities, is an important first step in ensuring soil health and resilience in these managed landscapes., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Aguiar et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Water quality plays an important role in river habitats. This study revealed the annual and seasonal variations and trend prediction of water quality in the middle Yangtze River after the third impoundment stage of the Three Gorges Reservoir. Multivariate statistical methods including principal component analysis/factor analysis (PCA/FA), Mann-Kendall (M-K) tests, discriminant analysis (DA), rescaled range (R/S) analysis, and the Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI) were used. Herein, eight water quality constituents including pH, electrical conductivity (EC), chloride (Cl), dissolved oxygen (DO), ammonia nitrogen (NH 3 N), total phosphorus (TP), water temperature (T), and permanganate index (CODmn) were monthly monitored in the Jiujiang hydrological transaction during 2010-2019. The information of eight water quality constituents, related to salinity, nutrient status, and oxidation reactions efficiency, was extracted. Water quality status remained as fair-good during 2010-2019 based on the results of CCME-WQI, with the seasonal significance ranked as T > DO > Cl > pH > EC > TP > NH 3 N > CODmn. In the future decade, annual average T was predicted to continue to increase although it might decrease in the wet season. EC was predicted to continue increasing annually especially in the wet season while Cl might decrease. NH 3 N and TP might maintain a significant decreasing trend in the future wet and dry seasons. DO maintained significantly increasing especially in the future dry seasons, whereas CODmn will continue to decrease annually and seasonally. The continued alkalization trend of waterbody was predicted, which is more significant in the wet season. The results provide helpful references for the ecological protection of the middle Yangtze River., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

This study focuses on understanding the role of passive wastewater treatment (wastewater lagoon plus wetland) in reducing the phosphorus discharge levels in a northern small community in Manitoba, Canada. The facultative lagoon system of that small community treats domestic wastewater and seasonally discharges effluent into a wetland that connects to Lake Manitoba . This research assesses phosphorus removal efficiency through the natural wetland during the vegetation growing season. The average total phosphorus (TP) concentration reduction for the observed treatment area of 1.3 ha was more than 70%, achieving the desired TP discharge concentration below 1 mg/L. Data analysis showed that the main accumulation of TP occurred at the 21-40 cm soil depth, which indicates the potential of natural wetland treatment applications under cold continental climate conditions as an effluent polishing step to satisfy regulatory requirements for phosphorus reduction.

Assessment of river quality has been attracting a great deal of attention because of its important implications for the living environment of human beings and aquatic organisms. This study investigated the spatial and temporal variation of water quality and its possible driving factors of Guanting Reservoir Basin. For this purpose, water quality was assessed with the Canadian Council of Ministers of the Environment Water Quality Index, together with nutrient inputs and social-economic data which were collected and analyzed during the period 2009-2019. The results showed that the overall water quality in Guanting Reservoir increased over time and was rated as "good" during the studied decade. Spatially, water quality in tributary upstream of Yanghe River and Sanggan River was better than that in Guishui River, resulting in better quality in West Reservoir than in East Reservoir. Among water quality indices, total nitrogen was the main pollutant affecting the water quality of the studied area. In addition, principal component analysis and correlation analysis were applied to evaluate the relationships between the socio-economic factors and water quality variation. Urbanization and industry structure were significantly correlated with the water quality variation in upstream tributaries. The findings provide insightful understanding into the spatio-temporal variations of water quality and the associated driving factors of Guanting Reservoir basin, which would help managers in executing theoretical reference for water quality protection., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Water quality plays an important role in estuarine habitats and affects aquatic organisms. The focus of this study was to understand the temporal-spatial variation of water quality and reveal the natural and anthropogenic drivers by using multiple analysis approaches. Herein, during 2012-2018, six water quality constituents (pH, electrical conductivity (EC), dissolved oxygen (DO), ammonia nitrogen (NH 3 N), total nitrogen (TN), and total phosphorus (TP) were examined for eight sites in the Yangtze Estuary, and the hydro-sediment data, i.e., discharge (Q) and sediment transport rate (STR), was collected from the upstream hydrological station Datong. The cluster analysis (CA), principal component analysis (PCA)/factor analysis (FA), Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI), and the Mann-Kendall (MK) test were applied. The eight sampling sites were geographically grouped into cluster I, cluster II, and cluster III based on the characteristics of water quality changes, which are under the influence of the upstream runoff, the anthropogenic activities, and seawater. The results are as follows: (1) NH 3 N, TN, and DO were key constituents representing the water quality of cluster I and cluster III, and those were EC, TN, and DO for cluster II; (2) The monthly-average Q and STR of Datong were negatively correlated to water quality constituents with seasonal variation except for pH; (3) The impact of anthropogenic activities on water quality was especially reflected in cluster III which is close to the Huangpu River Estuary; upstream runoff was the natural driver of water quality changes for cluster I while that was seawater for cluster II. Seawater acts a key role in affecting the water quality of cluster II situated at the North Branch. Revealing the key drivers of water quality change in the Yangtze Estuary provides a reference for water quality management., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In this article, the author discusses the landscape-scale patterns of the cyanobacterial toxin microcystin in Canadian lakes discovered by researchers through a regression tree model using the TREES module in the software SYSTAT 13. He mentions that the model helps to determine the relationship between microcystin concentrations, the concentration of total nitrogen (TN) to total phosphorus (TP) and the TN:TP ratio.

Fertilizer applications on lawns have raised environmental concerns in many Canadian municipalities. In this greenhouse study, NO 3 -N leaching losses from Kentucky bluegrass (Poa pratensis L.) lawns were evaluated on two soils (a schist loam and a clay loam) and on a sand/peat moss rootzone mix (80% sand, 20% peat moss). Eight different fertilizer N sources (urea, Polyon 8 and 12-wk release, Duration 45 and 90-d release, XCU, corn gluten meal, and UFLEXX) were assessed at five application rates (25-200 kg N ha -1  yr -1 ) and two application frequencies over two 8-wk trials. Average NO 3 -N concentration in leachate were measured at levels of 3.5, 7.4, and 1.4 mg L -1 from turf grown in loam, clay, and sand respectively, but losses from loam and clay were mostly affected by N mineralization from organic matter. Turf fertilized with rates ≥100 kg N ha -1 generally resulted in acceptable visual quality on both soils, but coated-urea fertilizers were more efficient to reduce leaching. In sand, UFLEXX and urea (150 and 200 kg N ha -1 ) as well as XCU (200 kg N ha -1 ) resulted in higher NO 3 -N losses, varying from 8.5 to 23.7 mg L -1 , and losses from other N sources were consistently below 3 mg L -1 . Our results show that it is possible to maintain good quality turfgrass while keeping low NO 3 -N leaching losses (i.e., <4 mg L -1 ) in loam, clay, and sand by selecting the ideal combination of N source, N rate, and application frequency., (© 2021 The Authors. Journal of Environmental Quality published by Wiley Periodicals LLC on behalf of American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.)

Climate mediated warming water temperature, drought and extreme flooding are projected to shift the phenology of nutrients in receiving lakes and reservoirs further intensifying eutrophication and algal blooms, especially in temperate reservoirs. An emerging issue in reservoir management is the prediction of climate change impacts, a necessity for sound decision making and sustainable management. Lake Diefenbaker is a large multipurpose reservoir in the Canadian Prairies. In this study, the impact of climate change on nutrient speciation in Lake Diefenbaker is examined using loosely linked SpAtially Referenced Regression On Watershed attributes (SPARROW) and CE-QUAL-W2 models. Two climate mediated scenarios, RCP 8.5 representing the most extreme climate change, and climate induced streamflow were modelled. Nutrient levels are anticipated to double under the climate change and streamflow scenarios. Winter and spring were identified as hot moments for nitrogen pollution with a plausible saturation of nitrous oxides in the future. Of concern is a plausible recycling of nitrate through dissimilatory nitrate reduction to ammonium. Summer and fall on the other hand represent the period for phosphorus enrichment and internal loading with a probable succession of cyanobacteria in the summer., (Copyright © 2021. Published by Elsevier Ltd.)

The Three Gorges Reservoir (TGR) underwent staged impoundment of water from 135 m to 175 m between 2003 and 2010. Periodic water impoundment was divided into drainage (March to early June), low water level (June to August), impoundment (September to October), and high water level (November to February) period. However, the impact of the Three Gorges Dam (TGD) and staged impoundment on water quality, especially in the long term, remains unclear. Herein, hydrological, pollution load, nutrient, and biochemical indices were determined for the TGR during 1998-2018. The Canadian Council of Ministers of the Environment Water Quality Index, a K-means clustering algorithm, and the Mann-Kendall (MK) test were applied to this data to explore the spatial and temporal distribution of water quality. The results show that water quality was good overall, but it before the full impoundment stage (2010) was worse than after that. The low water level period had the worst water quality among the four periods, and spatially, midstream was worst. Among water quality indices, the median total nitrogen (TN) and total phosphorus (TP) were in the range of 1.505-2.303 and 0.071-0.176 mg/L, respectively, and these were the key pollution indices. In addition, due to differences in hydrological and hydrodynamic conditions, and the regional distribution of pollution sources, water quality in the TGR displayed temporal and spatial heterogeneity. TN, TP, potassium permanganate index (COD Mn ), five-day biochemical oxygen demand (BOD 5 ) and Escherichia coli (E. coli) were maximal during the low water level period, and TN, TP and E. coli were highest in midstream. MK test results revealed that nutrients pollution became worse midstream, and a gradual increase in TP caused severe algal blooms downstream. Therefore, nutritional water treatment and non-point source pollution control should be the focus of future work., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

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. δ 15 N values of DIN in tributary water differed seasonally and were greatest during snowmelt. Incorporation of ammonium δ 15 N 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 δ 15 N 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 δ 15 N 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., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2020. Published by Elsevier B.V. All rights reserved.)

Finfish aquaculture is a source of dissolved nutrients, which can impact water quality in the wider environment. Therefore, the potential effects of dissolved nutrient loading must be considered if management is to transition towards an Ecosystem Approach to Aquaculture. In this study, the dissolved nitrogen dispersion pattern from a rainbow trout farm in Port Mouton (Nova Scotia, Canada) was simulated and evaluated in the context of potential toxicity for a foundation seagrass species. A range of scenarios defined under a precautionary approach were simulated using a fully spatial hydrodynamic model. These worst-case scenarios predicted a maximum nitrogen concentration at any moment of the day of 7.5 μM, which is below the expected toxicity threshold for seagrass. Further scenarios demonstrated that the increased dispersion caused by the wind could drop these values by 45-50% in the vicinity of the farm, suggesting the relevant role of wind forcing in nitrogen dispersion. This outcome suggests that the decline of seagrass reported in some parts of Port Mouton bay are unlikely to have been triggered by dissolved nutrients discharged from the farm. This case-study demonstrates the value of ecosystem modelling to make science-based and transparent decisions to implement an ecosystem approach to aquaculture., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study evaluates spatiotemporal variability in the behavior of septic system derived nutrients in a sandy nearshore aquifer and their discharge to a large lake. A groundwater nutrient-rich plume was monitored over a two-year period with the septic system origin of the plume confirmed using artificial sweeteners. High temporal variability in NO 3 -N attenuation in the nearshore aquifer prior to discharge to the lake (42-96%) reveals the complex behavior of NO 3 -N and potential importance of changing hydrological and geochemical conditions in controlling NO 3 -N discharge to the lake. While PO 4 -P was retarded in the nearshore aquifer, the PO 4 -P plume extended over 90 m downgradient of the septic system. It was estimated that the PO 4 -P plume may reach the lake within 10 years and represents a legacy issue whereby PO 4 -P loads to the lake may increase over time. To provide broader assessment of the contribution of septic systems to P and N loads to a large lake, a regional scale geospatial model was developed that considers the locations of individual septic systems along the Canadian Lake Erie shoreline. The estimated P and N loads indicate that septic systems along the shoreline are only a minor contributor to the annual P and N loads to Lake Erie. However, it is possible that nutrients from septic systems may contribute to localized algal blooms in shoreline areas with high septic system density. In addition, disproportionate P and N loads in discharging groundwater may change the N:P ratio in nearshore waters and promote growth of harmful cyanobacteria. The study provides new insights into factors controlling the function of the reaction zone near the groundwater-lake interface including its impact on groundwater-derived nutrient inputs to large lakes. Further, the study findings are needed to inform septic system and nutrient management programs aimed at reducing lake eutrophication., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

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.

Statistical modeling is commonly used to relate the performance of potato (Solanum tuberosum L.) to fertilizer requirements. Prescribing optimal nutrient doses is challenging because of the involvement of many variables including weather, soils, land management, genotypes, and severity of pests and diseases. Where sufficient data are available, machine learning algorithms can be used to predict crop performance. The objective of this study was to determine an optimal model predicting nitrogen, phosphorus and potassium requirements for high tuber yield and quality (size and specific gravity) as impacted by weather, soils and land management variables. We exploited a data set of 273 field experiments conducted from 1979 to 2017 in Quebec (Canada). We developed, evaluated and compared predictions from a hierarchical Mitscherlich model, k-nearest neighbors, random forest, neural networks and Gaussian processes. Machine learning models returned R2 values of 0.49-0.59 for tuber marketable yield prediction, which were higher than the Mitscherlich model R2 (0.37). The models were more likely to predict medium-size tubers (R2 = 0.60-0.69) and tuber specific gravity (R2 = 0.58-0.67) than large-size tubers (R2 = 0.55-0.64) and marketable yield. Response surfaces from the Mitscherlich model, neural networks and Gaussian processes returned smooth responses that agreed more with actual evidence than discontinuous curves derived from k-nearest neighbors and random forest models. When conditioned to obtain optimal dosages from dose-response surfaces given constant weather, soil and land management conditions, some disagreements occurred between models. Due to their built-in ability to develop recommendations within a probabilistic risk-assessment framework, Gaussian processes stood out as the most promising algorithm to support decisions that minimize economic or agronomic risks., Competing Interests: The authors have declared that no competing interests exist. All the funders (Natural Sciences and Engineering Council of Canada, Quebec Ministry of Agriculture, Fisheries and Food, Centre SEVE, Patate Dolbec Inc., Groupe Gosselin FG, Agriparmentier Inc., Patate Laurentienne, Ferme Bergeron-Niquet, and Patates Lac-St-Jean) have declared that no competing interests exist. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Wetland buffer zones (WBZs) are riparian areas that form a transition between terrestrial and aquatic environments and are well-known to remove agricultural water pollutants such as nitrogen (N) and phosphorus (P). This review attempts to merge and compare data on the nutrient load, nutrient loss and nutrient removal and/or retention from multiple studies of various WBZs termed as riparian mineral soil wetlands, groundwater-charged peatlands (i.e. fens) and floodplains. Two different soil types ('organic' and 'mineral'), four different main water sources ('groundwater', 'precipitation', 'surface runoff/drain discharge', and 'river inundation') and three different vegetation classes ('arboraceous', 'herbaceous' and 'aerenchymous') were considered separately for data analysis. The studied WBZs are situated within the temperate and continental climatic regions that are commonly found in northern-central Europe, northern USA and Canada. Surprisingly, only weak differences for the nutrient removal/retention capability were found if the three WBZ types were directly compared. The results of our study reveal that for example the nitrate retention efficiency of organic soils (53 ± 28%; mean ± sd) is only slightly higher than that of mineral soils (50 ± 32%). Variance in load had a stronger influence than soil type on the N retention in WBZs. However, organic soils in fens tend to be sources of dissolved organic N and soluble reactive P, particularly when the fens have become degraded due to drainage and past agricultural usage. The detailed consideration of water sources indicated that average nitrate removal efficiencies were highest for ground water (76 ± 25%) and lowest for river water (35 ± 24%). No significant pattern for P retention emerged; however, the highest absolute removal appeared if the P source was river water. The harvesting of vegetation will minimise potential P loss from rewetted WBZs and plant biomass yield may promote circular economy value chains and provide compensation to land owners for restored land now unsuitable for conventional farming., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

One of the main factors of the increased eutrophication level of surface waters is the high anthropogenic loads of biogenic substances discharged into water bodies. Municipal wastewaters, containing large amounts of nitrogen and phosphorus play one of the key roles in the acceleration of eutrophication intensity. The main direction in the prevention of eutrophication caused by wastewater discharge has become the reduction of nutrient loads introduced to wastewater receivers in accordance with strict legal requirements achievable only in advanced technologies. The treated wastewater quality standards are actually developed for total nitrogen and total phosphorus content, disregarding the fact that eutrophication potential of treated wastewater is determined by the content of non-organic nutrient forms directly bioavailable for water vegetation. That is why the currently used energy-consuming and expensive technologies do not always guarantee effective protection against eutrophication and its consequences. The goal of the study was to analyze the most widely used wastewater treatment technologies for enhanced biological nutrients removal in treated wastewater eutrophication potential. For this purpose, an analysis of the operation of 18 wastewater treatment plants based on different technologies in Finland, Canada, Poland, Russia and the United States was realized. The analysis concluded that the eutrophication potential of treated wastewater to a large extent is conditioned by the applied technology. The results of the research concluded that the eutrophication potential can serve an important criterion for decision-making regarding the proper selection of wastewater treatment technologies aimed at eutrophication mitigation.

Marine management interventions are increasingly being implemented with the explicit goal of rebuilding ocean ecosystems, but early responses may begin with alterations in ecological interactions preceding detectable changes in population-level characteristics. To establish a baseline from which to monitor the effects of spatial protection on reef fish trophic ecology and track future ecosystem-level changes, we quantified temperate reef fish densities, size, biomass, diets and isotopic signatures at nine sites nested within two fished and one five-year old marine protected area (MPA) on the northwest coast of Canada. We calculated rockfish (Sebastes spp.) community and species-specific niche breadth for fished and protected areas based on δ13C and δ15N values. We found that rockfish community niche width was greater inside the MPA relative to adjacent fished reefs due to an expanded nitrogen range, possibly reflecting early changes in trophic interactions following five years of spatial protection. Our data also demonstrated that the MPA had a positive effect on the δ15N signature of rockfish (i.e., trophic position), but the effect of rockfish length on its own was not well-supported. In addition, we found a positive interaction between rockfish length and δ15N signature, such that δ15N signatures of rockfish caught within the MPA increased more rapidly with body size than those caught in fished areas. Differences in rockfish size structure and biomass among fished and unfished areas were not clearly evident. Species of rockfish and lingcod varied in trophic and size responses, indicating that life-history traits play an important role in predicting MPA effects. These results may suggest early changes in trophic behavior of slow-growing rockfish due to predation risk by faster growing higher trophic level predators such as lingcod inside MPAs established on temperate reefs. Consequently, spatial protection may restore both the trophic and behavioral roles of previously fished consumers earlier and in measurable ways sooner than observable changes in abundance and size., Competing Interests: The authors have declared that no competing interests exist.

We present the first geomicrobiological characterization of the meromictic water column of Powell Lake (British Columbia, Canada), a former fjord, which has been stably stratified since the last glacial period. Its deepest layers (300-350 m) retain isolated, relict seawater from that period. Fine-scale vertical profiling of the water chemistry and microbial communities allowed subdivision of the water column into distinct geomicrobiological zones. These zones were further characterized by phylogenetic and functional marker genes from amplicon and shotgun metagenome sequencing. Binning of metagenomic reads allowed the linkage of function to specific taxonomic groups. Statistical analyses (analysis of similarities, Bray-Curtis similarity) confirmed that the microbial community structure followed closely the geochemical zonation. Yet, our characterization of the genetic potential relevant to carbon, nitrogen and sulphur cycling of each zone revealed unexpected features, including potential for facultative anaerobic methylotrophy, nitrogen fixation despite high ammonium concentrations and potential micro-aerobic nitrifiers within the chemocline. At the oxic-suboxic interface, facultative anaerobic potential was found in the widespread freshwater lineage acI (Actinobacteria), suggesting intriguing ecophysiological similarities to the marine SAR11. Evolutionary divergent lineages among diverse phyla were identified in the ancient seawater zone and may indicate novel adaptations to this unusual environment., (© 2019 Society for Applied Microbiology and John Wiley & Sons Ltd.)

Nitrogen loading has been linked to eutrophication and seagrass bed declines worldwide, yet early warning signs and potential mitigating factors are often less clear. Our objective was to use published nitrogen loading model results together with eelgrass habitat surveys from 7 bays in Atlantic Canada to assess linkages between nitrogen loading, tidal flushing and bivalve aquaculture on observed eutrophication indicators in eelgrass habitats. Field surveys revealed significant differences in primary indicators (annual algae, tissue nitrogen) and secondary changes in eelgrass bed structure, yet no large loss of eelgrass cover or biomass. Multivariate analyses found positive correlations between nitrogen loading and eutrophication indicators, with distinct clusters of high- and low-impact sites, and the mitigating effects of flushing time and aquaculture. Our results highlight that combining measures of nitrogen loading, eutrophication indicators and mitigating factors can help detect early warning signs and assess eutrophication risk to inform management and conservation of coastal ecosystems before significant losses of seagrass occurs., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Eutrophication of an under-ice river-lake system in Canada has been modeled using the Water Quality Analysis Simulation Program (WASP7). The model was used to assess the potential effect on water quality of increasing inter-basin transfer of water from an upstream reservoir into the Qu'Appelle River system. Although water is currently transferred, the need for increased transfer is a possibility under future water management scenarios to meet water demands in the region. Output from the model indicated that flow augmentation could decrease total ammonia and orthophosphate concentrations especially at Buffalo Pound Lake throughout the year. This is because the water being transferred has lower concentrations of these nutrients than the Qu'Appelle River system, although there is complex interplay between the more dilute chemistry, and the potential to increase loads by increasing flows. A global sensitivity analysis indicated that the model output for the lake component was more sensitive to input parameters than was the model output of the river component. Sensitive parameters included dissolved organic nitrogen mineralization rate, phytoplankton nitrogen to carbon ratio, phosphorus-to-carbon ratio, maximum phytoplankton growth rate, and phytoplankton death rate. Parameter sensitivities on output variables for the lake component were similar for both summer (open water) and winter (ice-covered), whereas those for the river component were different. The complex interplay of water quality, ice behaviors, and hydrodynamics of the chained river-lake system was all coupled in WASP7. Mean absolute error varied from 0.03-0.08 NH 4 -N/L for ammonium to 0.5 to1.7 mg/L for oxygen, and 0.04-0.13 NO 3 -N/L for nitrate.

Levels of biomagnifying contaminants are greatest in high-trophic level biota (e.g., predatory birds such as gulls). Gull eggs have been used to assess contaminant spatial patterns and sources, but such assessments must consider how organism trophic position may influence spatial inferences. Stable nitrogen isotopes (δ 15 N) in bulk tissue are routinely used in this context. However, bulk δ 15 N values are only useful if spatial differences in baseline δ 15 N values are considered. Amino acid compound-specific stable nitrogen isotope analysis can generate estimates of baseline δ 15 N values and trophic position from the same sample. In the present study, eggs (n = 428) of California (Larus californicus), herring (Larus argentatus smithsonianus), and ring-billed (Larus delawarensis) gulls were used to assess spatial patterns in mercury (Hg) availability in 12 western Canadian lakes located over 14 degrees of latitude, with amino acid compound-specific stable isotope analysis adjustment of egg Hg levels for trophic position. Mean trophic position-adjusted egg Hg levels (micrograms per gram, dry wt) were greatest at sites in receiving waters of the Athabasca River (X¯ = 0.70) compared to southern (X¯ = 0.39) and northern (X¯ = 0.50) regions. Research is required to investigate factors (e.g., local Hg released as a result of human activities, processes influencing Hg methylation) which may be responsible for greater Hg availability in the lower Athabasca River basin. However, it is clear that amino acid compound-specific stable isotope analysis is a valuable tool for assessing contaminant spatial patterns. Environ Toxicol Chem 2018;37:1466-1475. © 2018 SETAC., (© 2018 SETAC.)

An improved version of the Eastern Canadian Diatom Index (IDEC: Indice Diatomées de l'Est du Canada) was developed, incorporating modifications to optimize diatom-based monitoring in Eastern Canada. The most significant improvement with this version of the IDEC is the extended coverage area including additional reference sites. This new version of the IDEC also incorporated a simplified list of diatom taxa to reduce the variability among analysts as it gains in popularity. Rare taxa (<2%) were excluded and various morphotypes were grouped. The index was created based on three sub-indices that were adapted to cover the range of natural pH and conductivity values allowing us to partial out the strong influence of natural pH and conductivity from the general pollution gradient. The index was created using 648 diatom assemblages including those from nearly 150 reference (or least-disturbed) sites. The reference sites covered a large range of natural characteristics. The diatom assemblages collected in these environments constitute "biotype class A" in each sub-index and represent a realistic goal for restoration. Associated total phosphorus and total nitrogen showed that class A generally reflects conditions that are considered oligotrophic (<0.025 mg L(-1)) or oligo-mesotrophic, while class D at the opposite end of the pollution gradient reflects eutrophic or hyper-eutrophic environments. There is a good correspondence between IDEC values and nutrient criteria, water quality indices based on physico-chemistry measurements, the presence of agricultural activities, and urban areas. The IDEC has a great potential to assist water quality monitoring, particularly when the objective is to assess the trophic status of a watercourse., (Copyright © 2013. Published by Elsevier B.V.)

Regina, Saskatchewan, Canada (population 190,400) treats its sewage at a modern sewage treatment plant (STP) on Wascana Creek. In the winter, treated sewage effluent makes up almost 100% of stream flow. Four surveys conducted from 2005 to 2007, in differing seasons, indicated significantly higher nitrogen (N) and phosphorus (P) concentrations at sites downstream of the STP compared to an upstream control site. Downstream, Wascana Creek is N hypersaturated (total dissolved N >3 mg/L) and soluble reactive phosphorus (SRP) makes up a greater percentage of total P (TP). Diminished nutrient retention capacities for both N and P are directly attributable to STP effluent. Creek SRP concentrations are less than estimates of equilibrium P concentrations (EPC(o)), indicating that creek sediments may be a source of P, further exacerbating hypereutrophic ambient SRP concentrations. As well, NO(2) + NO(3)-N concentrations far surpass World Health Organization limits for drinking water (10 mg/L) and sensitive taxa, while NH(3)-N, NH(4)-N, and NO(2) + NO(3)-N exceed Canadian Water Quality Guidelines for Protection of Aquatic Life and those for the U.S. Environmental Protection Agency. High NH(4)-N concentrations may be responsible for depressions not only in algal biomass and production observed downstream but reductions in primary to bacterial production ratios (PP:BP). In spring and fall, these reductions push PP:BP from net autotrophy to heterotrophy. The Wascana Creek study highlights the considerable problems associated with excess nutrients in effluent-dominated ecosystems (EDS). It also underlines the need for better controls on NH(4)-N additions from STPs in such EDS, especially in a day and age when freshwater supplies are dwindling and negative effects of climate change are expected., (© 2010 SETAC.)

With increasing amounts of nitrogen (N) being added to farmland in the form of fertilizer and manure to optimize crop yields, and more broadly, to meet the growing demands for food, feed and energy, there are public concerns regarding its possible negative impact on the environment. An optimal balance between N requirements for production versus efficient N use is required, so as to minimize N losses from the agricultural system. An agri-environmental indicator i.e., the Indicator of the Risk of Water Contamination by Nitrogen (IROWC-N) was developed to assess the risk of N moving from agricultural areas into groundwater and/or nearby surface water bodies. The indicator linked the quantity of mineral nitrogen remaining in the soil at harvest, i.e., the Residual Soil Nitrogen (RSN) indicator, and the subsequent climatic conditions during the winter period. The results were assessed in terms of nitrate lost through leaching and nitrate concentration in the drainage water, expressed in five IROWC-N risk classes. Unlike previous versions of the indicator, the current model provided a more complete description of the soil-water balance, including the calculation of rainfall interception by crops, surface runoff, actual evapotranspiration and soil-water contents. Consequently, the current IROWC-N estimates differed markedly from those obtained previously. Between 1981 and 2006, the risk of water contamination by N in Canada was small, and reflected what was happening in the three Prairie provinces where 85% of Canada's farmland is located. However, the aggregated IROWC-N index, which is a combination of all five risk classes, increased steadily by 2.3% per year, from 6.7 in 1981 to 10.6 in 2006. The proportion of farmland in the very low IROWC-N risk class decreased from 88 to 78%; correspondingly, the proportion in the low risk class increased from 2 to 12%. The proportion of farmland in the moderate-, high- and very high-risk classes changed by less than 3% over time. The trends in IROWC-N in the Atlantic provinces were significantly worse than the national trend; for example, in Atlantic Canada, the aggregated IROWC-N index tripled from 27.8 in 1981 to 87.5 in 2006. Increases in fertilizer use (except in British Columbia), increases in livestock numbers in Manitoba and the Atlantic provinces, and an increase in legume crop acreage were the main factors that contributed to the increase in IROWC-N estimates. Climatic factors were also involved, as droughts reduced yields, N uptake and N leaching in many regions of Canada in 2001.

A reliable method for measuring (15)N/(14)N and (2)H/(1)H ratios of nicotine in cigarette tobacco has been developed. It involves a simple procedure for extracting nicotine from tobacco using methanol. The extract is directly analyzed on a gas chromatography isotope ratio mass spectrometer (GC-IRMS). The method is reproducible with 4% RSD for delta(2)H and delta(15)N. Brand name cigarettes manufactured in Canada (N = 47) and in China (N = 23) have been analyzed. The results show that nicotine from Canadian cigarettes has a higher (2)H/(1)H ratio and a lower (15)N/(14)N ratio than the Chinese cigarettes. The delta(2)H values for Canadian cigarettes range from -232.7 per thousand to -203.4 per thousand with an average of -222.1 per thousand; the delta(2)H values for Chinese cigarettes range from -262.6 per thousand to -219.9 per thousand with an average of -243.8 per thousand. The delta(15)N values for Canadian cigarettes range from -7.7 per thousand to -6.3 per thousand with an average of -7.1 per thousand; the delta(15)N values for Chinese cigarettes range from -7.6 per thousand to -5.7 per thousand with an average of -6.3 per thousand. The combined measurements of (2)H/(1)H and (15)N/(14)N have been shown to be useful in identifying counterfeits of Canadian cigarettes analyzed in this study.

Inputs of nutrients (phosphorus, P, and nitrogen, N) to coastal and fresh waters can accelerate eutrophication, resulting in excessive aquatic plant growth, depletion of oxygen, and deleterious changes in abundance and diversity of organisms. Using long-term (approximately 1995-2005) monitoring data from agriculturally-dominated watersheds in southern Ontario and Quebec, Canada, we developed and tested several approaches for setting targets for N and P. Our research showed that it is possible to set scientifically-credible targets for total P and total N to protect ecological condition of streams in agricultural landscapes, and define achievable targets attainable following adoption of beneficial management practices., (Copyright (c) Environment Canada 2008.)

The Human Monitoring Laboratory (HML) has developed a method to measure the liquid nitrogen boil-off rate from the whole body counter's single dewar as a function of time. The device consists of a commercially available instrument that was modified to fit the HML's whole body counter's dewar; unfortunately, the modification was not perfect requiring an alternative approach to using the maximum fill value. The boil-off rate is now measured by taking two measurements and calculating the loss rate. Resulting boil-off rates are plotted on a control chart so that long-term trends can be easily assessed.

The objective of this study is to estimate the soil N flux from the vadose zone to the aquifer of the Wilmot watershed (Prince Edward Island, Canada) for a typical three-year cropping rotation (barley-red clover-potato). A conceptual model estimates that 199-221 tons of N were yearly available for leaching at the watershed scale. A significant portion of this N amount was available for leaching at the end of the crop season representing 80-90% of the annual N balance. Drainage water nitrate concentrations were significantly higher after the potato-rotation year than during the crop season. Low nitrate concentrations were measured at spring thaw indicating that most of the nitrate available from the preceding potato crop season was likely leached at the end of fall or during winter. Early spring ionic exchange membrane sampling show a large availability of nitrate in soil possibly throughout winter as well, resulting from soil N mineralization and nitrification over the winter period. These findings are corroborated by the isotope natural abundance analysis of nitrate in groundwater implying that nitrifiers are significantly active during winter, as well as during the crop season, and that leaching of soil nitrates with seasonal signals takes place whenever recharge is occurring.

The aim of this study was to assess the phenotypic level of lactose and milk urea nitrogen concentration (MUN) and the association of these traits with functional survival of Canadian dairy cattle using a Weibull proportional hazards model. A total of 1,568,952 test-day records from 283,958 multiparous Holstein cows from 4,758 herds, and 79,036 test-day records from 26,784 multiparous Ayrshire cows from 384 herds, calving from 2001 to 2004, were used for the phenotypic analysis. The overall average lactose percentage and MUN for Ayrshires were 4.49% and 12.20 mg/dL, respectively. The corresponding figures for Holsteins were 4.58% and 11.11 mg/dL. Concentration of MUN increased with parity number, whereas lactose percentage decreased in later parities. Data for survival analysis consisted of 39,536 first-lactation cows from 1,619 herds from 2,755 sires for Holsteins and 2,093 cows in 228 herds from 157 sires for Ayrshires. Test-day lactose percentage and MUN were averaged within first lactation. Average lactose percentage and MUN were grouped into 5 classes (low, medium-low, medium, medium-high, and high) based on mean and standard deviation values. The statistical model included the effects of stage of lactation, season of production, the annual change in herd size, type of milk-recording supervision, age at first calving, effects of milk, fat, and protein yields calculated as within herd-year-parity deviations, herd-year-season of calving, lactose percentage and MUN classes, and sire. The relative culling rate was calculated for animals in each class after accounting for the remaining effects included in the model. Results showed that there was a statistically significant association between lactose percentage and MUN in first lactation with functional survival in both breeds. Ayrshire cows with high and low concentration of MUN tended to be culled at a higher than average rate. Instead, Holstein cows had a linear association, with decreasing relative risk of culling with increasing levels of MUN concentration. The relationship between lactose percentage and survival was similar across breeds, with higher risk of culling at low level of lactose, and lower risk of culling at high level of lactose percentage.

Annual export rates, or fluxes, of total nitrogen (TN), nitrate, total phosphorus (TP) and potassium from four streams on two golf courses on the Precambrian Shield were compared with those from forested reference locations. Overall, the mean annual fluxes of K, TN, NO(3) and TP from golf courses were greater than from forested areas by 10, 2, 6 and 2 times, respectively. The overall mean export coefficients (kg/ha/yr) were 16 for K, 5.2 for TN, 2.1 for NO(3) and 0.14 for TP. For TN and TP, these are similar to those reported from cropland in Canada by Chambers and Dale.

To assess the concern over declining base cation levels in forest soils caused by acid deposition, input-output budgets (1990s average) for sulphate (SO(4)), inorganic nitrogen (NO(3)-N; NH(4)-N), calcium (Ca), magnesium (Mg) and potassium (K) were synthesised for 21 forested catchments from 17 regions in Canada, the United States and Europe. Trend analysis was conducted on monthly ion concentrations in deposition and runoff when more than 9 years of data were available (14 regions, 17 sites). Annual average SO(4) deposition during the 1990s ranged between 7.3 and 28.4 kg ha(-1) per year, and inorganic nitrogen (N) deposition was between 2.8 and 13.8 kg ha(-1) per year, of which 41-67% was nitrate (NO(3)-N). Over the period of record, SO(4) concentration in deposition decreased in 13/14 (13 out of 14 total) regions and SO(4) in runoff decreased at 14/17 catchments. In contrast, NO(3)-N concentrations in deposition decreased in only 1/14 regions, while NH(4)-N concentration patterns varied; increasing at 3/14 regions and decreasing at 2/14 regions. Nitrate concentrations in runoff decreased at 4/17 catchments and increased at only 1 site, whereas runoff levels of NH(4)-N increased at 5/17 catchments. Decreasing trends in deposition were also recorded for Ca, Mg, and K at many of the catchments and on an equivalent basis, accounted for up to 131% (median 22%) of the decrease in acid anion deposition. Base cation concentrations in streams generally declined over time, with significant decreases in Ca, Mg and K occurring at 8, 9 and 7 of 17 sites respectively, which accounted for up to 133% (median 48%) of the decrease in acid anion concentration. Sulphate export exceeded input at 18/21 catchments, likely due to dry deposition and/or internal sources. The majority of N in deposition (31-100%; median 94%) was retained in the catchments, although there was a tendency for greater NO(3)-N leaching at sites receiving higher (<7 kg ha(-1) per year) bulk inorganic N deposition. Mass balance calculations show that export of Ca and Mg in runoff exceeds input at all 21 catchments, but K export only exceeds input at 16/21 sites. Estimates of base cation weathering were available for 18 sites. When included in the mass balance calculation, Ca, Mg and K exports exceeded inputs at 14, 10 and 2 sites respectively. Annual Ca and Mg losses represent appreciable proportions of the current exchangeable soil Ca and Mg pools, although losses at some of the sites likely occur from weathering reactions beneath the rooting zone and there is considerable uncertainty associated with mineral weathering estimates. Critical loads for sulphur (S) and N, using a critical base cation to aluminium ratio of 10 in soil solution, are currently exceeded at 7 of the 18 sites with base cation weathering estimates. Despite reductions in SO(4) and H(+) deposition, mass balance estimates indicate that acid deposition continues to acidify soils in many regions with losses of Ca and Mg of primary concern.

The New England Governors and Eastern Canadian Premiers (NEG/ECP) adopted the Acid Rain Action Plan in June 1998, and issued a series of action items to support its work toward a reduction of sulfur dioxide (SO(2)) and nitrogen oxide (NO(x)) emissions in northeastern North America. One of these action items was the preparation of an updated critical load map using data from lakes in the NEG/ECP area. Critical load maps provide a more complete index of the surface water sensitivity to acidification. Combined sulfur and nitrogen critical loads and deposition exceedances were computed using Henriksen's Steady-State Water Chemistry (SSWC) model. Results show that 28% of all 2053 lakes studied have a critical load of 20 kg/ha/year or less, making them vulnerable to acid deposition. Emission reductions, and more specifically SO(2) emission reductions have proven beneficial because critical loads were exceeded in 2002 for 12.3% of all studied lakes. Those lakes are located in the more sensitive areas where geology is carbonate-poor. Of these lakes, 2.9% will never recover even with a complete removal of SO(4) deposition. Recovery from acidification for the remaining 9.4% of the lakes will require additional emission SO(2) reductions.