Rivers are the primary contributor to marine plastics, transporting litter from inland sources through natural drainage systems. Despite an agreement among researchers that waste littered on land has the potential to enter river systems, there lacks specific quantification of the forces that facilitate transport. Although meteorological conditions (e.g. wind, rain) are considered factors, this exploratory study theorises that the influence of movement of individuals through an urban environment deserves investigation. To illustrate this hypothesis, litter items fitted with Global Positioning System (GPS) were released in an area of high foot traffic along the river Thames in Central London during a time of low meteorological influence. Point data were analysed through a Standard Deviational Ellipse (SDE) to quantify distance, speed and direction of travel of litter items under the sole influence of human movement. Of the 9 bottles distributed, 5 remained in the test site undisturbed by street cleansing staff. During this time, bottles travelled an average distance of 2.4 metres in directions consistent with the flow of foot traffic; two of which ultimately entering the river as a result of these forces. Although the study is limited, results imply proof of concept that passive anthropogenic forces contribute to riverine litter loads, calling into question public complicity when ignoring or kicking litter. It is suggested that packaging be designed with qualities that reduce transportability and the use of physical barriers along river edges be implemented as means to reduce the contribution of terrestrial litter to marine plastics.

Species reintroductions can play a major role in addressing biodiversity declines. Fish species reintroductions are, however, complex and require the investigation of multiple factors: physical habitat, water chemistry and hydrology, among others. The burbot (Lota lota, L.), the only freshwater member of the Cod family (Gadidae), was extirpated from English rivers due to habitat modification, leading to a loss of suitable spawning and larval nursery habitat. This paper uses a bespoke field survey, grounded in burbot ecology, to assess instream habitat availability for a proposed English burbot reintroduction site, the River Wissey, eastern England. Using an ex situ assessment, the study compares the Wissey in terms of floodplain spawning and larval nursery habitats with three Belgian sites where a burbot reintroduction is on-going. The study found that the English candidate reintroduction site had 10% of the main channel habitat available for instream spawning, with 15% available for juveniles, 20% for adults and 42% classified as unsuitable for any life stage. The floodplain habitat analysis determined that the English reintroduction site had a potential floodplain spawning habitat capacity of 56%, compared to < 42% at the Belgian comparison sites. Overall, habitat associated with each burbot life stage is present at the English candidate reintroduction site. Based solely on physical river habitat, this paper recommends river restoration before the reintroduction is attempted to increase connectivity between extant good-quality habitat patches and between the main channel and floodplain. To achieve a successful burbot reintroduction, it is concluded that more research is needed on hydrological and thermal dynamics, as well as food-web interactions.

The 2020 mass mortality of 350 African elephants (Loxodonta africana) in Botswana sparked global concern, with cyanotoxins in watering holes (pans) being a suspected cause, though evidence remains inconclusive. Combining remote sensing and spatial analysis, we examined the relationship between the ecohydrology of ∼3000 pans and the locations of deceased elephants. Our analysis revealed a significant difference in the spatial distribution of fresh versus decayed carcasses (p < 0.001), indicating that the die-off deviated from typical regional elephant mortality patterns. We identified 20 pans near fresh carcasses that experienced increased cyanobacteria bloom events in 2020 (n = 123) compared to the previous 3 years combined (n = 23), exhibiting the highest average phytoplankton biomass of the period 2015–2023 (Normalised Difference Chlorophyll Index >0.2). These findings suggest a heightened risk and likelihood of cyanotoxin presence in these pans. Elephants were estimated to have walked 16.5 km (± 6.2 km) and died within 88 h (± 33 h) of exposure. Our study provides evidence that cyanobacterial toxicity could be a contributing factor to the 2020 die-off, while also considering other potential causes, and offers a general framework for investigation of future mortality events. We underscore the need to integrate spatial analysis and regional ecohydrological assessments to monitor and mitigate animal mortality events and inform conservation strategies.

Study region: 375 lakes across the East African Rift System Study focus: East African Rift System lakes provide a critical region of freshwater biodiversity and support the livelihoods of millions of people. Since 2010, water levels have risen at many Kenyan Rift System lakes flooding settlements, destroying infrastructure and impacting biodiversity, whereas several Ethiopian lakes experienced declining water levels, threatening water availability. However, water storage changes have not been quantified and the drivers of hydrological change have not been assessed on a regional scale. Here, we used satellite Earth observation and open-access data products to quantify changes in lake water volumes, total catchment water storage anomalies and environmental drivers for 375 lakes across the East African Rift System from 2000 to 2023. New hydrological insights for the region: Water storage increased across central East Africa and declined in the south of the Rift System, with lake surface areas increasing by a total of 71,822 km2 and water volumes increasing by 1375.2 km3. Increasing rainfall (Coef = 1.775, SE = 0.571, p = 0.002) and urban development (Coef = 6.270, SE = 2.260, p = 0.006) caused expanding lake surface areas, whereas population growth within catchments reduced both lake surface areas (Coef = -7.023, SE = 2.210, p = 0.002) and water volumes (Coef = -8.735, SE = 3.578, p = 0.020). Increasing rainfall trends (Coef = 4.454, SE = 1.733, p = 0.020) and the expansion of catchment forest cover (Coef = 11.284, SE = 5.263, p = 0.047) facilitated greater water storage within lake basins. With more extreme wet seasons and longer dry seasons predicted for East Africa under climate change, sustainable catchment management is required to mitigate both future flooding and drought events.

Transmission teaching which centres around traditional lecturing discounts the variety of different learners and individual aptitudes. Physical Geography as a discipline has historically provided a range of teaching methods beyond lecturing which embrace field and laboratory activities, frequently adapting new research technologies to further student learning. While technological trends are increasing the demand for Geography graduates with GIS, modelling, or programming skills, Geography lecturers should remain open to using other technological advances as teaching tools. Using an example of low-cost environmental sensors, this paper demonstrates how technologically-focused exercises can effectively solidify a range of geographical skills through experiential learning. Using Kolb's Experiential Learning Model to identify the key learning processes, we compare low-cost environmental sensor training to the UK's current Quality Assurance Agency for Higher Education's (QAA) Geography benchmarks. We also consider the practical applications of this technology as a learning tool for Physical Geography. In comparison with a student evaluation, this paper provides an initial basis to support additional qualitative investigations into the learning outcomes of independent, technology-based learning activities.

East African lakes support the food and water security of millions of people. Yet, a lack of continuous long-term water quality data for these waterbodies impedes their sustainable management. While satellite-based water quality retrieval methods have been developed for lakes globally, African lakes are typically underrepresented in training data, limiting the applicability of existing methods to the region. Hence, this study aimed to (1) assess the accuracy of existing and newly developed water quality band algorithms for East African lakes and (2) make satellite-derived water quality information easily accessible through a Google Earth Engine application (app), named LAndsat water QUality retrieval tool for east African lakes (LAQUA). We collated a dataset of existing and newly collected in situ surface water quality samples from seven lakes to develop and test Landsat water quality retrieval models. Twenty-one published algorithms were evaluated and compared with newly developed linear and quadratic regression models, to determine the most suitable Landsat band algorithms for chlorophyll-a, total suspended solids (TSS), and Secchi disk depth (SDD) for East African lakes. The three-band algorithm, parameterised using data for East African lakes, proved the most suitable for chlorophyll-a retrieval (R2 = 0.717, p < 0.001, RMSE = 22.917 μg/L), a novel index developed in this study, the Modified Suspended Matter Index (MSMI), was the most accurate for TSS retrieval (R2 = 0.822, p < 0.001, RMSE = 9.006 mg/L), and an existing global model was the most accurate for SDD estimation (R2 = 0.933, p < 0.001, RMSE = 0.073 m). The LAQUA app we developed provides easy access to the best performing retrieval models, facilitating the use of water quality information for management and evidence-informed policy making for East African lakes.

Soda lakes are some of the most productive aquatic ecosystems.1 Their alkaline-saline waters sustain unique phytoplankton communities2,3 and provide vital habitats for highly specialized biodiversity including invertebrates, endemic fish species, and Lesser Flamingos (Phoeniconaias minor).1,4 More than three-quarters of Lesser Flamingos inhabit the soda lakes of East Africa5; however, populations are in decline.6 Declines could be attributed to their highly specialized diet of cyanobacteria7 and dependence on a network of soda lake feeding habitats that are highly sensitive to climate fluctuations and catchment degradation.8,9,10,11,12 However, changing habitat availability has not been assessed due to a lack of in situ water quality and hydrology data and the irregular monitoring of these waterbodies.13 Here, we combine satellite Earth observations and Lesser Flamingo abundance observations to quantify spatial and temporal trends in productivity and ecosystem health over multiple decades at 22 soda lakes across East Africa. We found that Lesser Flamingo distributions are best explained by phytoplankton biomass, an indicator of food availability. However, timeseries analyses revealed significant declines in phytoplankton biomass from 1999 to 2022, most likely driven by substantial rises in lake water levels. Declining productivity has reduced the availability of healthy soda lake ecosystems, most notably in equatorial Kenya and northern Tanzania. Our results highlight the increasing vulnerability of Lesser Flamingos and other soda lake biodiversity in East Africa, particularly with increased rainfall predicted under climate change.14,15,16 Without improved lake monitoring and catchment management practices, soda lake ecosystems could be pushed beyond their environmental tolerances.Video abstract

The objective of this study is to analyze the spatial–temporal patterns, identify risk zones and explore the co-occurrence correlation of eight heavy metals (HMs) in urban rivers in nine river systems of China using a meta-analysis. A spatial–temporal analysis was conducted to analyze the variation trend of publications and HMs. Health risk and ecological risk assessment models were used to identify risk zones in river water and sediment, respectively. A co-occurrence network analysis was conducted to determine the co-occurrence correlation of HMs. The results demonstrated that cadmium (Cd), chromium (Cr) and mercury (Hg) in river water in the Huaihe (region 5) and Haihe River systems were 20–40 times higher than the environmental quality standards; Hg, Cd, copper (Cu) and zinc (Zn) were heavily accumulated in sediments in the Songliao (region 1), Yellow River (region 3) and Southeast Drainage (region 9) systems. Cr in river water in region 5 posed carcinogenic risks to urban residents through ingestion and dermal contact, while Cd and Cu posed high ecological risks in the sediments in regions 1, 3, 5 and 9. Multiple HMs exhibited significant co-occurrence correlations. In river water, the average clustering coefficients among lead (Pb), Cu, Zn, Cd, Cr and nickel ranged from 0.51 to 0.76. In sediments, eight HMs exhibited even more significant correlations, ranging from 0.34 to 0.81 (p < 0.05). The coexistence and strong correlation of HMs in urban river systems may exacerbate their potential risks. Hg and Cd were the top polluting elements in urban rivers in China. Cd in urban river sediments posed significant ecological risks at the national level. Significant correlations (r > 0.5) between HMs were found in urban rivers.

Litter is a pervasive social and environmental issue that continues to evade effective and sustainable mitigation strategies. As the nature of waste items can influence methods and rates of littering, an understanding of litter typologies associated with specific sites has the potential to inform targeted anti-littering efforts. In this study, data analysis methods from ecology were applied to litter surveys to evaluate patterns among urban litter items found in two types of streets in England (High Streets and Central Business Districts). The results indicate that sites characterised as a High Street (predominantly leisure activities such as shopping and dining) contained lower densities and less variety yet featured litter items with a higher potential for environmental contamination than sites categorised as Central Business Districts (identified by high numbers of professional workers and transport links). Although litter was significantly different between sites, the litter community structure was not. Our results suggest that litter typologies and associated activities can lead to specific knowledge of key influential items in a site and inform future evidence-based and sustainable mitigation systems.

Accurate hydrological data with high spatial resolution is important for flood risk and water resource management, particularly under the context of climate change. The cost of monitoring networks, as well as the characteristics of the hydrological environment itself, can be a barrier to meeting these data requirements, however. This study covers the design and testing of a low-cost, “build-it-yourself”, instream water depth sensor providing an assessment of its potential in future hydrological monitoring projects. The low-cost sensor was built using an Arduino microcontroller, a differential pressure sensor and a thermistor, a real-time clock, and an SD card module. The low-cost logger was deployed in tandem with a factory-calibrated Solinst®LevelLogger® 5 Junior for 6 months in the River Wissey, UK. We found the mean absolute error of the Arduino-based logger relative to the commercial setup to be ±0.69 cm for water depth and ±0.415 °C for water temperature. Economically, the Arduino-based logger offers an advantage, costing a total of £133.35 (USD 168.26 at time of publication) comparative to the industrial comparison’s cost of £408 (USD 514.83 at time of publication). This study concludes that the low cost of the Arduino-based logger gives a strong advantage to its incorporation in hydrological data collection, if the trade-offs (i.e., time investment and accuracy) are considered acceptable and appropriate for a project.

The 2020 mass mortality of 350 African elephants (Loxodonta africana) in Botswana sparked global concern. These deaths have been linked to cyanobacterial toxins (cyanotoxins) in local watering holes (pans), but evidence remains inconclusive. Our study presents the first detailed spatial analysis that explores the relationship between the ecohydrology of 3,389 regional pans with the locations of deceased elephants. Our findings reveal a significant difference in the distribution of fresh versus older elephant carcasses (p < 0.001), suggesting that the die-off event deviates from typical regional patterns of elephant deaths. We identified twenty pans near the sites of fresh carcasses that experienced more phytoplankton (microalgae or cyanobacteria) bloom events in 2020 (n = 123) compared to the previous 3 years combined (n = 23), exhibiting the highest average phytoplankton biomass of the period 2015-2023 (Normalised Difference Chlorophyll Index > 0.2; p < 0.001). These findings suggest a high risk and likelihood of cyanotoxins as the poisoning source. Our spatial analysis indicates elephants walked an average of 16.5 km (± 6.2 km) and died within 88 hours (± 33 hours) from initial exposure, offering metrics that were previously unknown for elephants. This study presents important new evidence that implicates cyanobacterial toxicity in the 2020 mass die-off and provides a general framework for investigation of future mortality events of large mammals. We underscore the need to integrate spatial analysis and ecohydrological assessments to better monitor and mitigate animal mortality events and inform conservation strategies.

ADVERTISEMENT RETURN TO ISSUEPREVHighlightNEXTMicropollutant Discharge from Combined Sewer Systems Will Increase with Storm FrequencyNic R. Bury*Nic R. BurySchool of Ocean and Earth Sciences, University of Southampton, Waterfront Campus, Southampton, United Kingdom SO14 3ZH*Email: [email protected]More by Nic R. BuryView Biographyhttps://orcid.org/0000-0001-6048-6338, Reegan CoppReegan CoppSchool of Ocean and Earth Sciences, University of Southampton, Waterfront Campus, Southampton, United Kingdom SO14 3ZHMore by Reegan CoppView Biography, Eloise BuckEloise BuckSchool of Ocean and Earth Sciences, University of Southampton, Waterfront Campus, Southampton, United Kingdom SO14 3ZHMore by Eloise BuckView Biography, Charlene DesouzaCharlene DesouzaSchool of Ocean and Earth Sciences, University of Southampton, Waterfront Campus, Southampton, United Kingdom SO14 3ZHMore by Charlene DesouzaView Biography, Amelia FerrariAmelia FerrariSchool of Ocean and Earth Sciences, University of Southampton, Waterfront Campus, Southampton, United Kingdom SO14 3ZHMore by Amelia FerrariView Biography, Frederick R. BuryFrederick R. BurySchool of Biological Sciences, University of Southampton, University Road, Southampton, United Kingdom SO17 1BJMore by Frederick R. BuryView Biography, and Michael A. ChadwickMichael A. ChadwickDepartment of Geography, King's College London, Bush House North East Wing, 30 Aldwych, London, United Kingdom WC2B 4BGMore by Michael A. ChadwickView BiographyCite this: Environ. Sci. Technol. Lett. 2023, 10, 10, 812–814Publication Date (Web):September 27, 2023Publication History Received5 September 2023Accepted21 September 2023Revised19 September 2023Published online27 September 2023Published inissue 10 October 2023https://pubs.acs.org/doi/10.1021/acs.estlett.3c00634https://doi.org/10.1021/acs.estlett.3c00634letterACS PublicationsCopyright © 2023 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views1038Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (5 MB) Get e-AlertscloseSupporting Info (2)»Supporting Information Supporting Information SUBJECTS:Natural resources,Pharmaceuticals,Sewage,Wastewater,Water treatment Get e-Alerts

Freshwater organisms in the Okavango Delta and Lake Ngami (Botswana) provide direct and indirect benefits to people and the economy of the region. However, their existence could be potentially threatened by human activities (primarily, upstream water abstraction and planned hydropower structures) coupled with climate change. For their protection, it is essential to know their distribution, ecology, and status of the ecosystems that they inhabit. Publications that record taxa from the Delta at species level are scarce, particularly aquatic macroinvertebrates. Identifying organisms to species level can provide more accurate information for environmental monitoring and conservation programmes but requires significant training and expertise. Here, we present a comprehensive taxonomical review of 2204 freshwater species from the Okavango Delta and Lake Ngami, with additional 355 species found in other areas of Botswana that are likely to be present in the study region. We also compare the diversity of the Okavango Delta and Lake Ngami with two other tropical wetlands: the Pantanal (Brazil) and the Kakadu Region (Australia). We show that biodiversity in the Okavango Delta and Lake Ngami is higher than in previous estimates, with recorded species richness dominated by phytoplankton and macroinvertebrates. Most species are widespread across the system and southern Africa. The resulting database includes new records (Bryozoa, Porifera), information on species conservation status, habitat, ecology, distribution in continental Africa, site details and taxonomical notes. This will be an essential resource for researchers, conservation managers, policy makers and consultants investigating freshwater biodiversity in tropical wetlands in the region.

Antifouling paints may contain copper which prevents the attachment and growth of organisms on vessel hulls. In the study, estuarine copper concentrations and its dispersal are determined as well as whole-body copper burden of Mytilus edulis deployed at 8 sites in the estuary, following boat wash-down in Lymington estuary, United Kingdom. The copper concentrations half a meter away from a boat wash-down was quickly diluted within 4 h. But 24 h following a wash down, copper levels remained 10- to 20-fold elevated above the levels 30 m away from the source. Copper concentrations in the sediment half a meter from the point source were about 100-fold greater than within the marina but the marina sediment concentrations were still above the effect range low. Mortality of M. edulis was not observed, but copper body burden 24 h following a wash down event was up to tenfold elevated for 5 d before returning to normal within 21 d.

Dataset with 2,200 freshwater species from the Okavango Delta and Lake Ngami (Botswana), with additional 349 species found in other areas of Botswana that are likely to be present in the study region. The dataset covers the following groups: amphibians, birds, fishes, macroinvertebrates, macrophytes, mammals, reptiles, phytoplankton, and zooplankton. The following information is given for each species: status in the Okavango Delta and Lake Ngami (present/potentially present); conservation status globally, Phylum, Class, Order, Family, Genus, species name, cited synonyms, common name, habitat, presence in high water, presence in low water, ecology, distribution in continental Africa, confirmed locations in the Okavango Delta, site coordinates, references, notes.

Melanoides tuberculata sensu lato (Thiaridae) are polymorphic female-clonal snails of Asian and African origins that have invaded freshwaters worldwide, including those in Florida. Although the snails have been documented in Florida for at least 70 years, no studies have investigated whether the observed distribution is due to a single introduction or multiple independent invasions. Here, cytochrome oxidase I was used to measure genetic diversity within and among sites in Florida and compare genetic diversity between Florida and other regions of the world. We also examined the relationship between shell morphology and haplotype diversity to determine if shell morphs can serve as a proxy for haplotypes. In total, we recovered 8 haplotypes randomly distributed across populations in Florida. Phylogenetic reconstruction supported the hypothesis of multiple invasions by diverse representatives of the M. tuberculata species complex. In contrast, shell morphology was not found to be a useful phylogeographic character, with divergent haplotypes represented by similar shell forms. These results suggest that the observed invasion patterns in Florida are best explained by serial introductions, and that shell morphology cannot be used to predict haplotypes or reconstruct invasion history of Melanoides tuberculata s.l. and that extensive taxonomic revisions are needed to investigate invasion dynamics.

•Despite raised awareness, volumes of litter in the environment continue to rise.•Polite littering is when people place litter neatly in public spaces.•Observations of non-cigarette littering found 46% were littered politely.•In total 63% of littering was unintentional.•Unintentional littering is as detrimental as intentional or flagrant littering.

Ecosystem metabolism is a vital measurement for understanding the dynamics of aquatic environments. China has a range of aquatic resources and in the past two decades, there has been an increasing interest in ecosystem metabolism research. However, no studies have evaluated overall variation and environmental patterns which affect metabolism in China's vast range of aquatic systems. For this paper, we searched for articles with metabolism data for China's major rivers and coastal zones from 2000 to 2020. We identified 127 studies documenting ecosystem metabolism functions including primary production (PP), community respiration (CR) and net ecosystem production (NEP). Using path analysis, we documented relationships across a range of environmental parameters. Light availability affected riverine and coastal PP (<0.1-10.7 gC m(-2) day(-1)), while riverine PP was also linked to precipitation, photosynthesis-related biomass, and land-use variables. Riverine and coastal CR ranged from 0.01 to 24.3 gC m(-2) day(-1) and was affected strongly by nutrient concentrations. Average NEP ranged from 2.9 to 9.2 gC m(-2) day(-1), suggesting the potential of some of the evaluated ecosystems to be CO2 sinks. Within this review, the large spatiotemporal range allows for a wide-ranging understanding of the variation of metabolic processes which contribute to CO2 dynamics and the role of aquatic ecosystems in regional climate change. Additionally, by evaluating aquatic ecosystem metabolism across such a diverse range of environmental conditions this work provides a scientific basis for future assessments of ecological risks under the complex conditions of climate change.This article is categorized under:Science of Water > Water QualityScience of Water > Water and Environmental ChangeWater and Life > Nature of Freshwater Ecosystems

Abstract Raptors can thrive in cities where food supplies are abundant and seasonally stable. The availability of such resources may be linked to spatiotemporally predictable human activities generating reliable food subsidies for both raptors and their prey, capable of sustaining large populations. However, raptors may become affected by shifts in human behaviour. Here, we explore how urban peregrine falcon Falco peregrinus diets respond to changes in human activity levels amidst COVID‐19 pandemic social restrictions. We used online nest cameras to study peregrine diets and reproduction across 31 sites in 27 UK cities over three breeding seasons, including one during lockdown. Prey composition changed significantly between years, and these differences varied by region. During lockdown, London peregrines took a lower proportion of pigeons (−14.5%), offset by a greater proportion of starlings Sturnus vulgaris (+6.9%) and ring‐necked parakeets Psittacula krameri (+3.2%). In other cities, lockdown diets showed no change for pigeons (+0.3%), starlings comprised a lower prey proportion (−4.3%), while non‐dominant corvid prey (+2.3%) and waterbirds (+2%) had greater importance. Racing pigeon prey also decreased during lockdown, significantly outside London. However, breeding parameters (number of eggs, hatchlings, fledglings) were not significantly different, suggesting urban peregrines may not have experienced food shortages amidst restrictions. Thus, our study demonstrates that human activity can influence urban peregrine predation opportunities but is unlikely to be more important than other factors like habitat availability. It also highlights how impacts can vary regionally, which may have been driven by social and geographical differences between the capital and other cities. Read the free Plain Language Summary for this article on the Journal blog.

This study evaluated nutrient flux (nitrate (NO3−), ammonium (NH4+), phosphate (PO43−), and dissolved organic carbon (DOC) at the sediment-water interface and river ecosystem metabolism (REM) to investigate how these ecological functions vary in Beijing’s urban waterways. Three tributaries of the River Beiyun were selected. Water quality varied across the study sites as each receives a mixture of wastewater treatment plant (WWTP) effluents and tributary inflows. A chamber technique was applied where water-specific nutrient concentrations were measured at two exposure times (3 and 10 min). Under the actions of physical and biological processes, NO3− and NH4+ flux was primarily controlled by equilibrium concentration and the N-cycle. However, bioabsorption appeared to regulate DOC flux. Specifically, NO3− flux ranged from −0.31 to +0.30 mg/(m2·s), NH4+ was −0.01 to +0.05 mg/(m2·s), PO43− was −0.01 to +0.01 mg/(m2·s), DOC was −0.04 to +0.13 mg/(m2·s). We applied the nighttime slope regression to estimate gross primary production (GPP) and ecosystem respiration (ER). Except in summer, net ecosystem production (GPP+ER) less than 0 indicated heterotrophic study reaches. Structural equation modelling revealed that nutrient dynamics and water temperature were the primary factors driving REM. Our study provides the needed systems-based understanding of vital ecological processes to improve in-stream management.