Stream Health Research Articles

Effective Stream Health Assessment: Soil Microbes Versus Aquatic Insects

Effective Stream Health Assessment: Soil Microbes Versus Aquatic Insects

Health assessment using aqua-quality indicators of alpine streams (Khunjerab National Park), Gilgit, Pakistan.

This preliminary research was conducted to evaluate the alpine stream health by using water quality as an indicator in Khunjerab National park of the Karakoram ranges located in Pak-China boarder Pakistan having altitude of 3660m. This study investigated the stream health in the context of the presence or absence of sensitive species, their diversity, and their taxa richness. The water and macroinvertebrate samples were collected from 17 different locations from upstream and downstream of the river by using random sampling method. Macroinvertebrate samples were obtained using kick net (500-μm mesh size) and hand-picking method (NYSDEC). A total of 710 counts including 41 families of macroinvertebrates were recorded comprising of 7 orders including: Ephemeroptera (46%) being the most dominant group, Plecoptera (33%), Trichoptera (5%), Chironomidae (Diptera) (14%), Heteroptera (1%), and Coleoptera (1%). Ephemeroptera, Trichoptera, and Plecoptera (EPT) were found in abundance at the main source, Qarchanai, Dhee, and Tourqeen Nullah, as compared to the other locations of the stream. The most dominant macroinvertebrate was Ephemeroptera whose relative abundance is Pi=0.49 by using the Shannon index. However, different statistical tools, including principal component analysis (PCA), cluster analysis (CA), ANOVA, and linear regression model, show a strong correlation between water quality and macroinvertebrates. The overall results of the biological indicators showed better ecological health at downstream compared to upstream. This study will provide basic information and understanding about the macroinvertebrates for future researchers, and the data will be helpful for upcoming research programs on alpine streams for the discovery and occurrences of macroinvertebrates and associated fauna.

Regional Ecological Health or Risk Assessments of Stream Ecosystems Using Biomarkers and Bioindicators of Target Species (Pale Chub)

Region-specific species are important as a target indicator to diagnose the ecological health or degree of impairment at various levels in aquatic ecosystems. An issue related to the selection of the target species, however, is that, if preliminary tests are not carried out, the species selected may not be an appropriate or representative candidate for biomarker or bioindicator analysis. This contribution outlines the screening process that culminated in the selection of pale chub (Zacco platypus) as the target species for evaluating ecological stream health in South Korea. Biochemical/blood chemistry response biomarkers and fish population and community model bioindicators were tested on the target species, and biomarker and bioindicator relationships with physical habitat health and water chemistry data were evaluated. A self-organizing map (SOM) was used to test the relevance of the target species. Overall, the results confirmed that the target species was suitable key indicator for regional ecological health assessments.

An influence of mesohabitat structures (pool, riffle, and run) and land-use pattern on the index of biological integrity in the Geum River watershed

Previous studies on the biological integrity on habitat and landuse patterns demonstrated ecological stream health in the view of regional or macrohabitat scale, thus ignored the mesoscale habitat patterns of pool, riffle, and runs in the stream health analysis. The objective of this study was to analyze influences on the mesohabitat structures of pool, riffle, and run reaches on the fish guilds and biological integrity in Geum-River Watershed. The mesohabitat structures of pool, riffle, and run reaches influenced the ecological stream health along with some close relations on the fish trophic and tolerance guilds. The mesoscale components altered chemical water quality such as nutrients (TN, TP) and BOD and these, then, determined the primary productions, based on the sestonic chlorophyll-a. The riffle-reach had good chemical conditions, but the pool-reach had nutrient enrichments. The riffle-reach had a predominance of insectivores, while the pool-reach has a predominance of omnivores. Also, the riffle-reach had high proportions of sensitive fish and insectivore fish, and the pool-reach had high proportions of tolerant species in the community composition. The intermediate fish species in tolerance and omnivorous fish species in the food linkage dominated the community in the watershed, and the sensitive and insectivorous fishes decreased rapidly with a degradation of the water quality. All the habitat patterns were largely determined by the land-use patterns in the watershed. Trophic guilds and tolerance guilds of fish were determined by land-use pattern and these determined the stream health, based on the Index of Biological Integrity. This study remarks the necessity to include additional variables to consider information provided by mesohabitats and land-use distributions within the selected stream stretch. Overall, our data suggest that land-use pattern and mesohabitat distribution are important factors to be considered for the trophic and tolerance fish compositions and chemical gradients as well as ecological stream health in the watershed.

Sustainable management of Great Lakes watersheds dominated by agricultural land use

Runoff of agricultural nutrients and sediments has led to re-eutrophication of lakes and impaired stream health in the Great Lakes Basin since around 2000 following earlier success in protecting water quality. Substantial investment in conservation actions has had insufficient impact, due in part to a limited basis for understanding the likely environmental outcomes of those investments. This article introduces a special section focusing on promoting investment that produces environmental outcomes as opposed to investing in conservation actions with unknown effects. The special section contains articles in three main categories: 1) studies based on fine-grain SWAT and other simulation modeling that can guide the type, amount, and location of conservation investments to increase their environmental impact; 2) edge-of-field measurement studies that provide updated knowledge to assist in further refining models to increase their predictive power; and 3) articles presenting innovative approaches to incentivizing outcome-oriented conservation investment. Implementation approaches discussed include certifying private crop nutrient advisors as recommending only appropriate timing, amount, and placement of nutrients; working within the existing public drain management system to incentivize conservation; and others. The special section shows that advances in SWAT modeling provide a powerful basis for targeting conservation investments to protect water quality in the Great Lakes Basin, while also demonstrating opportunities to further refine the models. It illustrates both the opportunity and the need to engage in more innovative institutional design of agricultural management programs that go beyond the traditional government programs and do more to reward outcomes and not just actions.

La descomposición de la hojarasca como herramienta para evaluar la integridad funcional de ríos altoandinos del sur del Ecuador

The ecological condition of tropical Andean rivers are threatened by many human activities including changes in land use and cover in watersheds. Current protocols diagnose the structural condition of streams but not their function. In this study we proposed an assessment tool using the leaf-litter breakdown as a measure of the functional condition and health of high Andean streams in Southern Ecuador, including methodology and threshold values adapted to local conditions. We selected 15 streams in three micro-basins (Mazán, Llaviuco and Matadero) within or in the vicinity of Cajas National Park where we deployed litterbags for 15, 28 and 64 days. We used two types of mesh (coarse and fine) for the litterbags in order to separate the contribution of macro-invertebrates and microorganisms in the decomposition process and also tested two different leaf substrates: Alder (Alnus acuminata) and Miconia (Miconia bracteolata). In each collection period we determined physical and chemical parameters, applied the riparian quality index (QBR-And) and river habitat index (IHF). Decomposition rates (-k) were determined from the time period at which approximately 50 % ash-free mass would have been lost. We used Ktotal and the ratio of the rate of decomposition between coarse and fine mesh (Kg/Kf) to define the functional condition thresholds. To test the metrics sensitivity we used graphical methods, one-way ANOVA and discriminative efficiency (ED). The analysis of watershed land-use and cover showed a gradient of intervention: Matadero ≥ Llaviuco > Mazán. The composition of the environmental variables of Mazán streams were different with respect to Llaviuco and Matadero, whose values were similar to each other. The QBR-And index showed a significant gradient from very low levels in Matadero (27.5), moderately high values in Llaviuco (66.5) to high values in Mazán (87). Alder leaf-litter breakdown rates were significantly faster in Mazán than in Matadero and Llaviuco streams, while breakdown rates of Miconia were not significantly different among watersheds. The Kg/Kf ratio was significantly higher in Mazán compared to Llaviuco and Matadero, which did not differ. We consider the Kg/Kf metric sensitive enough to discriminate impacts in the studied areas. Our results support the use of the leaf-litter breakdown as an appropriate tool to assess functional ecological condition, complementing the structural assessments of these Andean rivers.

Cattle use of perennial streams and associated riparian areas on a northeastern Oregon landscape

Stream and riparian health is a major concern for state and federal land management agencies that are charged with oversight of extensive land holdings in the mountain west of the United States. Several federal agencies in the 1980s and 1990s determined that livestock grazing had adversely impacted a majority of federal lands in this region. In response, management was changed on grazing allotments to focus on stream system health. Recent advanced global positioning system (GPS) logging capabilities, both accuracy and frequency/duration of logging, coupled with rapidly developing geographic information system (GIS) analytical capabilities allowed evaluation of livestock use of streams and riparian zones on mountain rangelands. This study was undertaken to clarify spatiotemporal characteristics of cattle use of perennial streams and associated riparian areas under current US Forest Service (USFS) management and to suggest managerial strategies with the potential to maintain or improve riverine environments. We initiated a five year study in 2008 to evaluate the use by cattle of 30 m (98.4 ft) and 60 m (196.9 ft) buffers on permanent streams on three extensive study sites in northeastern Oregon. The three study sites cover 43,972 ha (108,700 ac) within a broader region 120 km (74.5 mi) north-south by 50 km (31 mi) east-west. Ten randomly selected cows from herds grazing each site were fitted with GPS collars that recorded position, date, and time at approximately five minute intervals throughout the grazing season. Nearly 3,750,000 cow positions were collected on the allotments during the study. The relative occupancy of cattle in buffers along both sides of perennial streams were determined on an annual and monthly basis by site. Each position was tagged with the date and time of occurrence. Relative use within 30 m of the stream varied substantially from site to site (0.74% to 2.54%), month to month (0.00% to 5.21%), and year to year (0.86% to 2.13%). In some months, GPS data indicated that watering was nearly exclusive from streams. In other months, stream use was low or nil, and watering was from water developments, small springs, seeps, puddles, or other source. Cattle preferred to access streams at specific locations where streambank slope, the lack of physical obstructions, and solid footing facilitated water access.

Development and evaluation of a comprehensive drought index

Droughts are known as the world's costliest natural disasters impacting a variety of sectors. Despite their wide range of impacts, no universal drought definition has been defined. The goal of this study is to define a universal drought index that considers drought impacts on meteorological, agricultural, hydrological, and stream health categories. Additionally, predictive drought models are developed to capture both categorical (meteorological, hydrological, and agricultural) and overall impacts of drought. In order to achieve these goals, thirteen commonly used drought indices were aggregated to develop a universal drought index named MASH. The thirteen drought indices consist of four drought indices from each meteorological, hydrological, and agricultural categories, and one from the stream health category. Cluster analysis was performed to find the three closest indices in each category. Then the closest drought indices were averaged in each category to create the categorical drought score. Finally, the categorical drought scores were simply averaged to develop the MASH drought index. In order to develop predictive drought models for each category and MASH, the ReliefF algorithm was used to rank 90 variables and select the best variable set. Using the best variable set, the adaptive neuro-fuzzy inference system (ANFIS) was used to develop drought predictive models and their accuracy was examined using the 10-fold cross validation technique. The models' predictabilities ranged from R2 = 0.75 for MASH to R2 = 0.98 for the hydrological drought model. The results of this study can help managers to better position resources to cope with drought by reducing drought impacts on different sectors.

Physicochemical water quality characteristics in relation to land use pattern and point sources in the basin of the Dongjin River and the ecological health assessments using a fish multi-metric model

Little is known about how chemical water quality is associated with ecological stream health in relation to landuse patterns in a watershed. We evaluated spatial characteristics of water quality characteristics and the ecological health of Dongjin-River basin, Korea in relation to regional landuse pattern. The ecological health was assessed by the multi-metric model of Index of Biological Integrity (IBI), and the water chemistry data were compared with values obtained from the health model. Nutrient and organic matter pollution in Dongjin-River basin, Korea was influenced by land use pattern and the major point sources, so nutrients of TN and TP increased abruptly in Site 4 (Jeongeup Stream), which is directly influenced by wastewater treatment plants along with values of electric conductivity (EC), bacterial number, and sestonic chlorophyll-a. Similar results are shown in the downstream (S7) of Dongjin River. The degradation of chemical water quality in the downstream resulted in greater impairment of the ecological health, and these were also closely associated with the landuse pattern. Forest region had low nutrients (N, P), organic matter, and ionic content (as the EC), whereas urban and agricultural regions had opposite in the parameters. Linear regression analysis of the landuse (arable land; AL) on chemicals indicated that values of AL had positive linear relations with TP (R 2 = 0.643, p < 0.01), TN (R 2 = 0.502, p < 0.05), BOD (R 2 = 0.739, p < 0.01), and suspended solids (SS; (R 2 = 0.866, p < 0.01), and a negative relation with TDN:TDP ratios (R 2 = 0.719, p < 0.01). Chemical factors were closely associated with land use pattern in the watershed, and these factors influenced the ecological health, based on the multimetric fish IBI model. Overall, the impairments of water chemistry and the ecological health in Dongjin-River basin were mainly attributes to point-sources and land-use patterns.

Optimization of bioenergy crop selection and placement based on a stream health indicator using an evolutionary algorithm

The emission of greenhouse gases continues to amplify the impacts of global climate change. This has led to the increased focus on using renewable energy sources, such as biofuels, due to their lower impact on the environment. However, the production of biofuels can still have negative impacts on water resources. This study introduces a new strategy to optimize bioenergy landscapes while improving stream health for the region. To accomplish this, several hydrological models including the Soil and Water Assessment Tool, Hydrologic Integrity Tool, and Adaptive Neruro Fuzzy Inference System, were linked to develop stream health predictor models. These models are capable of estimating stream health scores based on the Index of Biological Integrity. The coupling of the aforementioned models was used to guide a genetic algorithm to design watershed-scale bioenergy landscapes. Thirteen bioenergy managements were considered based on the high probability of adaptation by farmers in the study area. Results from two thousand runs identified an optimum bioenergy crops placement that maximized the stream health for the Flint River Watershed in Michigan. The final overall stream health score was 50.93, which was improved from the current stream health score of 48.19. This was shown to be a significant improvement at the 1% significant level. For this final bioenergy landscape the most often used management was miscanthus (27.07%), followed by corn-soybean-rye (19.00%), corn stover-soybean (18.09%), and corn-soybean (16.43%). The technique introduced in this study can be successfully modified for use in different regions and can be used by stakeholders and decision makers to develop bioenergy landscapes that maximize stream health in the area of interest.

Defining drought in the context of stream health

Droughts affect many sectors, such as agriculture, economic, social, human health, and ecosystems. Many drought indices have been developed; yet, none of them quantifies the impacts of drought on stream health. The purpose of this study is to define a new drought index capable of assessing fish vulnerability. To accomplish this, a hydrological model, called the Soil and Water Assessment Tool (SWAT), and the Regional-scale Habitat Suitability model were integrated in order to understand the state of drought within 13,831 stream segments within the Saginaw Bay Watershed. The ReliefF algorithm was used as the variable selection method, and partial least squared regression was used to develop two sets of predictor models capable of determining current and future drought severities. Forty-seven different climate scenarios were used to investigate drought model predictability of future climate scenarios. The results indicated that the best drought model has a high capability for predicting future drought conditions with R2 values ranging from 0.86 to 0.89. In general, the majority of reaches (94%) will experience higher drought probability under future climate scenarios compared to current conditions. The procedure introduced in this study is transferable to other watersheds with regional standards for environmental flow to measure the impacts of drought on stream health.

Multiple stressor effects on stream health in the Lake Simcoe Watershed

The Lake Simcoe Watershed (LSW) is an important natural resource, supporting varied agricultural, recreational, and tourism activities for millions of people. Historically, major alterations to land uses have occurred throughout the watershed, resulting in increases of nutrients and contaminants, and alteration of hydrological and thermal regimes. The combination of these stressors has the potential to elicit greater impacts on ecosystem health than any one stressor in isolation, yet no studies have examined their effects on stream health and aquatic biota in the LSW. In this study, we quantified the impacts of multiple stressors on indices of biotic integrity, as well as assessments of benthic invertebrate and fish community composition from 2004 to 2012. Using a suite of multivariate analyses, we examined stressors across three categories of environmental variables: water quality, temperature, and hydrology. Water quality explained the largest amount of variation in stream health and biological community composition, followed by water temperature and hydrological variables, respectively. Total phosphorus, dissolved oxygen, and iron concentrations, as well as the 7-day low flow and the mean summer temperature, were identified as predictors of both fish and benthic invertebrate variance. Multiple stressor interactions were detected for fish communities, although these interactions were of lower relative importance than for individual stressors. In contrast, no significant stressor interactions were found to influence benthic invertebrate communities. Overall, our results reinforce the importance of ecosystem monitoring, and the need to consider the influence of multiple aspects of ecosystem function, when examining the health of aquatic systems.

Mitigation of the Environmental Health Risk on Military Air Bases Polluted with Hydrocarbons

AbstractThis paper presents the environmental and health threats caused by petroleum products as well as the results of remediation work on five air bases where biological cleaning methods developed by the authors were implemented. The aviation fuel leakages endangered the health of people and surface water streams at the sites as well as in distant locations. The aim of the research was to verify remediation techniques developed in laboratory tests. The initial concentration of total petroleum products in the soils reached 2,320–8,770 mg/kg of dry matter, which presented an extremely high risk to the population and the environment. The autochthonous bacterial strains, which included Pseudomonas fluorescens, Acinetobacter calcoaceticus, Pseudomonas putida I, and Pseudomonas putida II, were proven to be very effective in degrading the xenobiotics. The applied microorganisms in conjunction with the authors’ remediation techniques produced very successful results. In the technical ex situ and in situ tests,...

Elective single embryo transfer- the power of one.

Despite the highest historical live birth success rates for couples undergoing in vitro fertilization (IVF), there has been an epidemic of iatrogenic twin and higher order gestation conceived from this treatment. Continued improvement in cryopreservation techniques have allowed preservation of supernumerary embryos for use in future cycles, and refinements in culture systems and embryo selection have resulted in the transfer of fewer embryos while maintaining favorable pregnancy rates. The voluntary transfer of a single high quality embryo, elective single embryo transfer (eSET), has significantly reduced multiple gestation rates and maximized the rate of singleton pregnancy without compromising overall success rates. Although eSET is the standard of care in several developed countries, utilization in the United States has been slow. States with mandated IVF insurance have seen decreases in preterm birth rates yielding down stream health care savings. Herein, the evolution and future applications of this practice to reduce the risk of iatrogenic twins is reviewed.

Investigating EFL Learners’ Multiple Intelligences in the Preparatory Year at Taif University

The present paper aims to investigate the English as a foreign language (EFL) learners’ multiple intelligences (MIs) in the preparatory year at Taif University in Saudi Arabia, and to provide suggestions for EFL instructors to integrate MIs in their lesson plans for instructional use in the classroom. To achieve these purposes, the researcher attempted to answer three questions. The first question investigated the different types of MSs that EFL learners possess. The second question examined whether there were any statistically significant differences (a= 0.05) in EFL learners’ MIs due to stream (Humanities, Sciences and Health). The third question was an attempt to synthesize literature in order to suggest ways for instructors to integrate MIs in the EFL classroom. A questionnaire of 4- Likert Scale was used to gather data from four hundred and eighty two students to answer the first two questions. And content analysis was used to answer the third question. The collected data were analyzed in the form of descriptive statistics. The results revealed that students do not tend to have interest in musical and naturalistic intelligences. In addition, there were statistically significant differences among the streams in the perceptions of their MIs in favor of the health stream students. The researcher also synthesized literature and suggested a number of techniques and activities to help instructors integrate MIs in their plans. Based on the results, the researcher presented a number of conclusions and recommendations.

Community concordance between fishes and benthic macroinvertebrates among adventitious and ordinate tributaries of a major river system

We examined patterns of concordance between macroinvertebrate and fish communities among adventitious and ordinate tributaries of the Monongahela River in southwestern Pennsylvania in order to determine their efficacy as mutual surrogates for the assessment of ecosystem integrity. Fish, macroinvertebrates, and 19 water quality parameters were sampled from 20 streams. Collected data were analyzed by principal components analysis, redundancy analysis, and Ward’s distance clustering matrices to determine degrees of community concordance and similarity. Fish and macroinvertebrate communities were assessed utilizing Indices of Biotic Integrity (IBI) in order to compare stream ecosystem health as expressed by each index. Adventitious and ordinate macroinvertebrate communities largely clustered in like groups with adventitious tributaries dominated by the crustacean Gammarus sp. and ordinate streams dominated by the trichopteran, Hydropsyche sp. Adventitious communities were strongly influenced by elevated total alkalinity and total suspended solids; ordinate communities by contrast to elevated total organic carbon and specific conductance. Fish communities showed no significant relationship to water quality parameters among either tributary type, but often grouped with their nearest geographic neighbor. The respective indices revealed a discord between the two communities suggesting that neither community serves as a surrogate for the other as an indicator of stream health in this basin. Both communities appeared to be driven by differences in local environmental conditions.

Large-scale climate change vulnerability assessment of stream health

Freshwater streams are critical resources that provide multiple benefits to humans and aquatic biota alike. As climate changes, it is projected that changes to the hydrological cycle and water temperatures will affect individual biota and aquatic ecosystems as a whole. The goal of this study was to determine the extent of climate change impacts on stream ecosystems as represented by four commonly used stream health indicators (Ephemeroptera, Plecoptera, and Trichoptera taxa (EPT), Family Index of Biotic Integrity (FIBI), Hilsenhoff Biotic Index (HBI), and fish Index of Biotic Integrity (IBI)). Seven watersheds in Michigan were selected based on stream thermal regimes. The Soil and Water Assessment Tool was used to simulate streamflow and pollutant loads. Important variables for each thermal class were selected using a Bayesian variable selection method and used as inputs to adaptive neuro-fuzzy inference systems models of EPT, FIBI, HBI, and IBI. Finally, an ensemble of climate models from the Coupled Model Intercomparison Project Phase 5 were used to determine the impacts of climate on the stream health in 2020–2040 compared to 1980–2000. The risk of declining stream health was determined using cumulative distribution functions. A stream temperature regression model was also developed to assess potential changes in stream thermal regimes, which could cause shifts in composition of aquatic communities. Several flow regime variables, including those related to flow variability, duration of extreme events, and timing were mainly affected by changing climate. At the watershed scale, most indicators were relatively insensitive to changing climate and the magnitude of stream health decline was low. However, at the reach scale, there are many instances of high risk and large magnitude of declines in the stream health indicators. At the same time, several streams experienced changes in thermal class, mostly transitioning from cold-transitional and cool streams to warm streams. This research demonstrated the applicability of the stream health modeling process in performing a climate change impacts assessment.

Permafrost thaw and intense thermokarst activity decreases abundance of stream benthic macroinvertebrates.

Intensification of permafrost thaw has increased the frequency and magnitude of large permafrost slope disturbances (mega slumps) in glaciated terrain of northwestern Canada. Individual thermokarst disturbances up to 40ha in area have made large volumes of previously frozen sediments available for leaching and transport to adjacent streams, significantly increasing sediment and solute loads in these systems. To test the effects of this climate-sensitive disturbance regime on the ecology of Arctic streams, we explored the relationship between physical and chemical variables and benthic macroinvertebrate communities in disturbed and undisturbed stream reaches in the Peel Plateau, Northwest Territories, Canada. Highly disturbed and undisturbed stream reaches differed with respect to taxonomic composition and invertebrate abundance. Minimally disturbed reaches were not differentiated by these variables but rather were distributed along a disturbance gradient between highly disturbed and undisturbed sites. In particular, there was evidence of a strong negative relationship between macroinvertebrate abundance and total suspended solids, and a positive relationship between abundance and the distance from the disturbance. Increases in both sediments and nutrients appear to be the proximate cause of community differences in highly disturbed streams. Declines in macroinvertebrate abundance in response to slump activity have implications for the food webs of these systems, potentially leading to negative impacts on higher trophic levels, such as fish. Furthermore, the disturbance impacts on stream health can be expected to intensify as climate change increases the frequency and magnitude of thermokarst.

A comparative study of manufacturing and service sector supply chain integration via the uncertainty circle model

Purpose – The purpose of this paper is to investigate the differences and similarities between the manufacturing and services sectors in order to develop a methodology that can provide the opportunity for the transfer of best practice between the two sectors. This paper aims to describe an audit methodology capable of yielding objective comparisons of supply chain integration performance that can assist practitioners and academics to transfer learned solutions. Design/methodology/approach – A robust, site-based, multi-method supply chain diagnostic for detecting manufacturing supply chain system uncertainty was amended for the service sector in order to yield objective comparisons of the (normalised) supply chain integration performances of 119 organisations. Findings – The research confirms the value of using a lens enabled by the uncertainty circle model (UCM) for generating meaningful comparative supply chain performances. The research found that services do not always exhibit unique attributes which effectively bar manufacturing-based supply chain best practice from being adopted within the service sector. Originality/value – Combining the UCM and Quick Scan Audit Methodology approach has the potential to assist the spread of proven good practice across both sectors. The framework provides realistic and repeatable performance vectors, capable of aligning estimates of value stream health status even when comparing supply chains with differing objectives, configurations, and performance goals.

Thinking beyond the Bioreactor Box: Incorporating Stream Ecology into Edge-of-Field Nitrate Management.

Around the world, artificially drained agricultural lands are significant sources of reactive nitrogen to stream ecosystems, creating substantial stream health problems. One management strategy is the deployment of denitrification enhancement tools. Here, we evaluate the factors affecting the potential of denitrifying bioreactors to improve stream health and ecosystem services. The performance of bioreactors and the structure and functioning of stream biotic communities are linked by environmental parameters like dissolved oxygen and nitrate-nitrogen concentrations, dissolved organic carbon availability, flow and temperature regimes, and fine sediment accumulations. However, evidence of bioreactors' ability to improve waterway health and ecosystem services is lacking. To improve the potential of bioreactors to enhance desirable stream ecosystem functioning, future assessments of field-scale bioreactors should evaluate the influences of bioreactor performance on ecological indicators such as primary production, organic matter processing, stream metabolism, and invertebrate and fish assemblage structure and function. These stream health impact assessments should be conducted at ecologically relevant spatial and temporal scales. Bioreactors have great potential to make significant contributions to improving water quality, stream health, and ecosystem services if they are tailored to site-specific conditions and implemented strategically with land-based and stream-based mitigation tools within watersheds. This will involve combining economic, logistical, and ecological information in their implementation.