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Ecosystems that are coupled by reciprocal flows of energy and nutrient subsidies can be viewed as a single "meta-ecosystem." Despite these connections, the reciprocal flow of subsidies is greatly asymmetrical and seasonally pulsed. Here, we synthesize existing literature on stream-riparian meta-ecosystems to quantify global patterns of the amount of subsidy consumption by organisms, known as "allochthony." These resource flows are important since they can comprise a large portion of consumer diets, but can be disrupted by human modification of streams and riparian zones. Despite asymmetrical subsidy flows, we found stream and riparian consumer allochthony to be equivalent. Although both fish and stream invertebrates rely on seasonally pulsed allochthonous resources, we find allochthony varies seasonally only for fish, being nearly three times greater during the summer and fall than during the winter and spring. We also find that consumer allochthony varies with feeding traits for aquatic invertebrates, fish, and terrestrial arthropods, but not for terrestrial vertebrates. Finally, we find that allochthony varies by climate for aquatic invertebrates, being nearly twice as great in arid climates than in tropical climates, but not for fish. These findings are critical to understanding the consequences of global change, as ecosystem connections are being increasingly disrupted.

We initiate the investigation of the parameterized complexity of Diameter and Connectivity in the streaming paradigm. On the positive end, we show that knowing a vertex cover of size k allows for algorithms in the Adjacency List (AL) streaming model whose number of passes is constant and memory is O (log n) for any fixed k. Underlying these algorithms is a method to execute a breadth-first search in O (k) passes and O (k log n) bits of memory. On the negative end, we show that many other parameters lead to lower bounds in the AL model, where Ω (n / p) bits of memory is needed for any p-pass algorithm even for constant parameter values. In particular, this holds for graphs with a known modulator (deletion set) of constant size to a graph that has no induced subgraph isomorphic to a fixed graph H, for most H. For some cases, we can also show one-pass, Ω (n log n) bits of memory lower bounds. We also prove a much stronger Ω (n 2 / p) lower bound for Diameter on bipartite graphs. Finally, using the insights we developed into streaming parameterized graph exploration algorithms, we show a new streaming kernelization algorithm for computing a vertex cover of size k. This yields a kernel of 2k vertices (with O (k 2) edges) produced as a stream in poly (k) passes and only O (k log n) bits of memory. [ABSTRACT FROM AUTHOR]

Nutrient enrichment and climate warming threaten freshwater systems. Metabolic theory and the paradox of enrichment predict that both stressors independently can lead to simpler food‐webs having fewer nodes, shorter food‐chains and lower connectance, but cancel each other's effects when simultaneously present. Yet, these theoretical predictions remain untested in complex natural systems. We inferred the food‐web structure of 256 lakes and 373 streams from standardized fish community samplings in France. Contrary to theoretical predictions, we found that warming shortens fish food‐chain length and that this effect was magnified in enriched streams and lakes. Additionally, lakes experiencing enrichment exhibit lower connectance in their fish food‐webs. Our study suggests that warming and enrichment interact to magnify food‐web simplification in nature, raising further concerns about the fate of freshwater systems as climate change effects will dramatically increase in the coming decades. [ABSTRACT FROM AUTHOR]

Anthropogenic land use has caused a major crisis to the biodiversity of stream fishes in recent decades, especially with regard to biotic homogenisation. Understanding the response of stream fishes to anthropogenic land use will help to promptly implement effective conservation measures. In this study, we investigated the effects of agriculture on fish diversity in streams in the Wannan Mountains, China. We predicted that agriculture would influence fish diversity by affecting local habitat conditions. The results showed that habitat conditions (e.g. water temperature, water width, water depth) differed significantly between disturbed and reference sites. The disturbed sites had high species richness due to the addition of translocated species outpacing the loss of endemic species. Moreover, fish assemblages showed taxonomic differentiation accompanied by functional homogenisation, which mainly resulted from the addition of translocated species with redundant functional traits. However, the emergence of homogenisation shows a time delay. The biotic differentiation of fish assemblages in agroecosystems is temporary in the Wannan Mountains, and homogenisation may eventually develop as stress intensifies. Thus, it is urgent and necessary to take effective conservation measures to delay or prevent fish assemblages from worsening in agroecosystems before homogenisation develops. [ABSTRACT FROM AUTHOR]

Identifying areas expected to remain buffered from climate change and maintain biodiversity and ecological function (i.e., climate refugia) is important for climate adaptation planning. As structurally diverse transitional zones between terrestrial and aquatic environments, riparian areas are often biological hotspots and provide critical corridors for species movement, particularly in arid and semi‐arid regions. In our study region in the western and central USA, identifying riparian areas that could serve as climate refugia is a priority for wildlife managers. We mapped areas with connected riparian habitats that, based on landscape diversity and projected changes in summer temperatures and landscape runoff, are expected to serve as climate refugia. To incorporate uncertainty and balance the need for near‐ and long‐term planning, we mapped potential refugia for 2 future time periods (2040–2069, 2070–2099) based on 2 climate models that represented divergent but plausible climate outcomes. The approach we developed is not constrained by physiology or behavior of target species and can be used to identify areas expected to fare comparatively well under a wide range of future climate scenarios. Our approach can also be used to identify areas where restoration could increase riparian connectedness and climate resilience. [ABSTRACT FROM AUTHOR]

Nepal holds a high ichthyofaunal diversity, nevertheless, the molecular study of Nepalese fish is still in its early stages. The first record of a cyprinid fish species the Garra kempi Hora, 1921 for Nepal was reported from eastern Nepal's Lohandra River. Both morphology and molecular data affirmed the existence of G. kempi in Nepal's aquatic system. This species was previously reported from China (Tibet) and northern India. The maximum likelihood phylogenetic analysis and pairwise genetic distance based on Kimura 2 parameters using cytochrome oxidase subunit 1 (COI) segment sequences (665 bp) also confirmed the identity of the species as G. kempi. The COI sequences of specimens from Nepal formed a monophyletic clade with the sequence of G. kempi from northeastern India and the two contained a pairwise genetic distance of 1.8% only. The new record of G. kempi from Nepal warrants a detailed ichthyofaunal survey for documenting the fish diversity in Nepal. [ABSTRACT FROM AUTHOR]

Wood turtles (Glyptemys insculpta) are a species of conservation concern throughout their geographic distribution. Several studies have investigated individual‐level habitat selection of wood turtles in the Upper Midwest in the United States, but the effects of habitat characteristics on abundance are poorly understood. This information is needed to improve landscape‐level habitat management and conservation initiatives for the species. Our study aimed to identify important aquatic and terrestrial habitat characteristics and quantify their influence on abundance dynamics of adult wood turtles in the Laurentian Mixed Forest Province ecoregion of Wisconsin and Minnesota, USA. We collected standardized population survey data at 57 sites within the ecoregion between 2016 and 2022. We used N‐mixture models with a multi‐stage model selection procedure to assess the influence of aquatic and terrestrial predictors on abundance, including several 3‐dimensional forest structure metrics derived from airborne Light Detection and Ranging (LiDAR) data. Several aquatic and terrestrial habitat characteristics influenced local abundance patterns of adult wood turtles. The most influential aquatic predictors were stream velocity and stream width, and the most influential terrestrial predictors were mean return height and vertical coefficient of variation of height. Abundance was high at sites containing comparatively narrow streams with moderate velocities. The most supported terrestrial predictors were derived from LiDAR and indicate that complex forest structures support larger wood turtle populations. Our results can be used in forest management strategies to improve habitat quality for wood turtles, such as selective tree harvesting to increase structural diversity, and potentially identify robust populations in under‐surveyed areas. [ABSTRACT FROM AUTHOR]

Climate change is causing serious problems in various economic sectors in particular involving water management. For this reason, it is extremely important to conduct research to identify climate change trends and better understand them. This study was carried out in the Dim Stream basin in the Western Mediterranean region (Turkey), which is particularly vulnerable to climate change. The study used flow data from two flow observation stations (FOS) and meteorological records such as wind speed, average flow, precipitation, temperature, evaporation, radiation, and relative humidity for 1984-2017. These data showed the changes between flow and hydrometeorological variables using linear regression analysis, coefficient of variation, t-test and correlation analysis. It has been determined that there has been a rapid decrease in the average flow of the FOS number 09-006 since 1995 and the average flow of the FOS number 09-013 since 1999. Also, it was demonstrated that the average relative humidity (RH ave), average temperature (T ave), average precipitation (Pave), total precipitation (Pt) and maximum precipitation (P max) meteorological variables were most affected by climate change in the basin. Furthermore, it was found that the most changes were Qy ave (67.60%), T min (48.23%), P max (36.43%), P ave (33.91%), P t (33.90%), and RH ave (2.63%) in FOS numbered 09-013. Moreover, it was concluded that climate change variability had developed trends towards a rapid decrease in the flow values at the flow observation stations in Dim Stream. These results show that plans and measures for the efficient and sustainable management of water resources in this region must be implemented immediately. [ABSTRACT FROM AUTHOR]

Fishes are found in different lentic and lotic aquatic ecosystems. Determining the composition of fish communities is a crucial component of water quality evaluations and conservation strategies in flowing rivers. The present study is carried out to investigate fish species diversity, richness, and abundance in two second-order streams: Gereb Tsedo (GTS) and Elala in the Tekeze sub-basin. We collected fish with backpack electrofishing during August and December 2013 and March 2014. Fish species richness and the total number of species per stream and per microhabitat were calculated for each stream. Species diversity for each site was calculated using the Shannon index of diversity using the standard formula H’ = –Σpi ln (pi). Diversity data among habitats and streams were compared using one-way analysis of variance (ANOVA) and Tukey post hoc comparisons, using the statistical software package STATISTICA 11. A total of 6,554 specimens representing four species: Garra blanfordii, Grra ignestii, Garra dembecha and Garra aethiopica, were caught. They are all indigenous riverine fish species of the family Cyprinidae. Fish abundance was significantly higher in GTS than Elala stream (t-test, t = 1.444, df = 3, p < 0.05). Across the two streams, the overall relative fish abundance was higher in pools, with 53%, followed by runs and riffles with 35% and 12%, respectively. Garra blanfordii was dominant in pools while G. aethiopica was the least dominant. Stream and habitat types were likely the more important driving factors behind the observed patterns of diversity, although the impact of other, not evaluated variables cannot be excluded. Most likely, the observed patterns do not represent a signature of fish dispersal limitation given that almost all species were widely distributed across the study area.

Google Classroom has been frequently used as an e-learning platform to substitute for Learning Management System (LMS), and the use of its features (Classwork, Stream, People, etc.) varies among teachers with different goals, focuses, and familiarity. However, research has not addressed how the selection of Google Classroom features affects students learning experience. Therefore, this study was aimed at finding out how Google Classroom features should be used to better facilitate online learning among students in English as a foreign language (EFL) classes. The data for this research was collected from ten leading schools in Indonesia, and 373 students participated in this study. Two questionnaires were used and delivered online, i.e. a Google Classroom Use questionnaire with Google Classroom features, consisting of 23 items, and a Technology Acceptance Model (TAM) questionnaire specified for EFL, consisting of 21 items with four constructs, i.e. usefulness, ease of use, intention, and actual system of use. The data were analyzed using multiple linear regression model to determine the effect of each Google Classroom feature on students' perception of TAM indicators. The hypotheses were rejected at the significance level of 0.05. The research results show that there is a correlation between both variables. The results also show that Classwork and Stream features were significant predictors for almost all TAM indicators. In this case, Classwork feature covers learning activities, and Stream feature includes interaction or communication facilities. Based on these results, it can be suggested that e-learning needs to facilitate students learning activities (e.g., quizzes, assignments, materials, and schedules) and student interaction/communication (e.g., announcements, notices, discussions, and shared posts). The results of this study contribute to educators and e-learning developers to consider maximizing the use and design of learning activity and interaction features due to their significance in online learning. [ABSTRACT FROM AUTHOR]

Understanding the complex relationships between benthic algal communities and environmental factors is crucial for ecosystem management and conservation. In this study, we investigated benthic algal communities in the upper Red River Basin in China. We collected data on land use, topography and other factors at the watershed scales to gain a comprehensive understanding in the upper Red River Basin in China. Partial canonical correspondence analysis, partial redundancy analysis and variance partitioning analysis methods were used to assess the effects of watershed and local environmental factors on benthic algal communities and their variation. The percentage of landscape that was forest (F-PL), the percentage of landscape that was cropland (C-PL), the percentage of landscape that was water (W-PL), elevation, slope, pH and water level fluctuation (WF) were identified as significant factors affecting the distribution of benthic algal communities. The diversity of benthic algal communities were greatly affected by environmental factors as F-PL, W-PL, precipitation (Prcp), slope, permanganate index (CODMn) and index of substrate (IOS). Slope, F-PL and Prcp showed a positive correlation with species evenness and a negative correlation with community density. The characteristics of functional groups of benthic algae were also shown to be strongly influenced by C-PL and IOS. According to the variance decomposition (VPA) results, it can be seen that, although the explanatory power of individual local and watershed environmental factors was roughly similar, their joint explanatory power was relatively low. Therefore, the influence of watershed environmental factors on benthic algal communities should not be overlooked. [ABSTRACT FROM AUTHOR]

Livestock grazing is a major economic activity worldwide. Cattle frequently graze and congregate in watercourses and riparian areas because of the availability of water, shade and the quality and variety of forage, thereby altering the ecological condition of stream ecosystems. We have explored the effects of cattle intrusion on the environmental conditions and fish assemblages of four neotropical prairie streams from Argentina's Pampas region. At each stream, both ungrazed and grazed conditions were surveyed. Water quality, habitat structure, riparian vegetation and fish assemblages were sampled. Significant detrimental changes were observed in environmental conditions of grazed sites in contrast to ungrazed sites. Fish assemblage structure and function were also significantly influenced by the environmental conditions imposed by cattle intrusion. Our results reveal the magnitude and direction of environmental changes imposed by cattle intrusion in prairie streams and highlight several key aspects of fish assemblages and populations that change accordingly. Relevant aspects for conservation and management purposes of these fragile ecosystems, such as protection of riparian vegetation condition and the control of cattle access and social engagement, are discussed. [ABSTRACT FROM AUTHOR]

Nepal holds a high ichthyofaunal diversity, nevertheless, the molecular study of Nepalese fish is still in its early stages. The first record of a cyprinid fish species the Garra kempi Hora, 1921 for Nepal was reported from eastern Nepal's Lohandra River. Both morphology and molecular data affirmed the existence of G. kempi in Nepal's aquatic system. This species was previously reported from China (Tibet) and northern India. The maximum likelihood phylogenetic analysis and pairwise genetic distance based on Kimura 2 parameters using cytochrome oxidase subunit 1 (COI) segment sequences (665 bp) also confirmed the identity of the species as G. kempi. The COI sequences of specimens from Nepal formed a monophyletic clade with the sequence of G. kempi from northeastern India and the two contained a pairwise genetic distance of 1.8% only. The new record of G. kempi from Nepal warrants a detailed ichthyofaunal survey for documenting the fish diversity in Nepal. [ABSTRACT FROM AUTHOR]

This article explores intersections between the author's process of making art and the analytic relationship. The author makes correlations between witnessing a deeply moving impressionist painting, engaging in Jung's method of active imagination, and the experience of reverie and opening to the imagination in the clinical relationship. Opening to the unconscious, and relating consciously to what emerges, is an art and a dance that involves the capacity to play. When there are unconscious and conscious meetings, a creative process ensues and can constellate what Jung called the transcendent function, a process that often catalyzes personal transformation. In witnessing great art and engaging in a creative process within the analytic situation, there is a curiosity and willingness to be affected and bear uncertainty for the sake of new discoveries, as well as dedication to becoming a more whole human being. [ABSTRACT FROM AUTHOR]

Knowledge about the distributions of species and the variables influencing their occurrence is important for their management and conservation, but factors affecting occurrence can vary across the range of a species. Northwestern pond turtles (Actinemys marmorata) are widespread generalist turtles, but are nonetheless of conservation concern throughout their range. To better understand the distribution of northwestern pond turtles and introduced American bullfrogs (Lithobates catesbeianus), we surveyed streams on private timberlands of the interior foothills of northern California using visual encounter surveys and collecting samples of environmental DNA. We found that northwestern pond turtle occurrence was negatively related to elevation in our sampling frame. Detection probabilities with environmental DNA were approximately twice those of visual encounter surveys, but both methods were effective for detecting turtles in streams. American bullfrogs were detected in a single sample at each of 2 sites (one by environmental DNA, one by visual encounter surveys). Management for northwestern pond turtles in forest streams within our sample area will likely have the largest effect at lower elevation sites where turtles are most likely to occur. [ABSTRACT FROM AUTHOR]

Increased occurrence, size, and intensity of fire result in significant but variable changes to hydrology and material retention in watersheds with concomitant effects on stream biogeochemistry. In arid regions, seasonal and episodic precipitation results in intermittency in flows connecting watersheds to recipient streams that can delay the effects of fire on stream chemistry. We investigated how the spatial extent of fire within watersheds interacts with variability in amount and timing of precipitation to influence stream chemistry of three forested, montane watersheds in a monsoonal climate and four coastal, chaparral watersheds in a Mediterranean climate. We applied state-space models to estimate effects of precipitation, fire, and their interaction on stream chemistry up to five years following fire using 15 + years of monthly observations. Precipitation alone diluted specific conductance and flushed nitrate and phosphate to Mediterranean streams. Fire had positive and negative effects on specific conductance in both climates, whereas ammonium and nitrate concentrations increased following fire in Mediterranean streams. Fire and precipitation had positive interactive effects on specific conductance in monsoonal streams and on ammonium in Mediterranean streams. In most cases, the effects of fire and its interaction with precipitation persisted or were lagged 2–5 years. These results suggest that precipitation influences the timing and intensity of the effects of fire on stream solute dynamics in aridland watersheds, but these responses vary by climate, solute, and watershed characteristics. Time series models were applied to data from long-term monitoring that included observations before and after fire, yielding estimated effects of fire on aridland stream chemistry. This statistical approach captured effects of local-scale temporal variation, including delayed responses to fire, and may be used to reduce uncertainty in predicted responses of water quality under changing fire and precipitation regimes of arid lands. [ABSTRACT FROM AUTHOR]

The non-native vermiculated sailfin catfish Pterygoplichthys disjunctivus (Weber, 1991) is recorded for the first time in eastern Nepal's aquatic systems. Native to South America, the first reports of P. disjunctivus in Asia were recorded in India, with subsequent reports from Bangladesh, Hongkong, Indonesia, Malaysia, Singapore, Thailand and Vietnam. Our findings mark the first known occurrence of a non-native species of sailfin catfish in Nepal. The public, policy makers, researchers, and merchants of ornamental fish all need to be informed critically about the release of non-native fish into natural water systems in light of the concerns. Non-native fish may negatively affect native fish populations if released into natural waters. Therefore, it is imperative that strict measures must be taken to prevent the intentional or unintentional escape of non-native fish into Nepal's natural water systems. [ABSTRACT FROM AUTHOR]

Seasonal patterns in body condition may help identify sensitive time periods or environmental stressors in fishes. Our objectives were to document spatiotemporal patterns of body condition of wild and hatchery-released Rio Grande silvery minnows (Hybognathus amarus), an endangered species endemic to the Rio Grande basin of North America. We collected fish weekly or bi-weekly from February to September, 2017 through 2019, in the Rio Grande, New Mexico, USA. Our time-series spanned an extreme drought year in 2018, allowing us to observe changes in body condition in relation to markedly different flow conditions. We collected body measurements from 2520 RGSM during the 3 years of our study. Spatiotemporal patterns in body condition were evident among and within years and sampling reaches, but within-sample variation in body condition was high. Annual patterns did not appear to be related to annual flow regime. Recaptured hatchery-reared fish were in slightly lower body condition, but followed the same seasonal patterns as did wild fish. Contrary to our expectations, body condition in both females and males was higher during the extreme drought year of 2018. Body condition may not be useful for identifying environmental stressors in small-bodied, short-lived fishes because individual variability is greater than spatial or temporal variation. We examined seasonal patterns in body condition of Rio Grande silvery minnow over 3 years. Body condition may help predict spawning success or highlight human impacts to fish populations. Contrary to our expectations, fish body condition did not seem to be related to drought conditions, possibly because these small fish do not build an energy reserve before spawning. [ABSTRACT FROM AUTHOR]

River restoration programmes with the goal of conserving and rehabilitating inland fishes have a multi‐decadal history, but evaluation and synthesis of past restoration actions have been limited by a lack of monitoring and reporting. Given that calls for both monitoring and systematic reviews of restoration have increased, we were interested in the influence that restoration has had on improving conditions for riverine fishes resulting from long‐standing and increasingly prominent stressors. Our objectives were to (1) identify which stressors were targeted in river restoration efforts, (2) determine the proportion of published studies that articulate restoration goals and develop comparative monitoring designs for assessing the effects of restoration on fishes, and (3) conduct a meta‐analysis to synthesise fish responses to restoration projects.We assessed restoration effectiveness for increasing fish density and richness from peer‐reviewed papers published over the past decade using a global systematic review and meta‐analysis.We found that restoration actions addressed major stressors primarily by improving in‐stream habitat (37%), increasing in‐stream longitudinal connectivity (26%) and increasing lateral floodplain connections (9%). Although 81% of studies had comparative monitoring designs (i.e., before/after and control/impact) and stated restoration goals, only 40% of those studies reported sufficient data to be included in the meta‐analysis. Projects which increased in‐stream connectivity had the largest positive effect size on fish density and richness compared to in‐stream habitat improvements and increasing floodplain connections. Time since restoration and restoration size (i.e., geographical footprint) were not strong predictors of fish response effect sizes.Restoration effectiveness was highly variable among project types. Authors of studies included in the meta‐analysis often identified spatial or temporal scale of monitoring, overriding catchment conditions, and recolonisation potential as sources of variability and effectiveness in restoration outcomes. Systematic reporting of these and other covariates may help guide processes in restoration evaluation and provide valuable research insights. Despite increased emphasis on monitoring, incomplete data reporting limited the number of studies that could be included for quantitative meta‐analysis. Persistent emphasis on setting specific criteria (e.g., measurable outcomes of fish response) for restoration goals, project monitoring, data reporting, information sharing and collaborative projects is likely to continue to improve understanding of restoration effectiveness transferable to future endeavours.Our results can be used to support river restoration practitioners with evidence‐based information to evaluate the cost–benefit ratio of competing restoration priorities, and inform restoration planning and implementation for riverine fish. [ABSTRACT FROM AUTHOR]

Characterizing morphological features in shallow streams such as dunes and ripples is vital to studies on fluvial geomorphology and in-stream habitat assessments of stream ecology. The paper aimed to examine the feasibility of a conventional hyperspectral method called linear optimal band ratio analysis for capturing the detailed morphologies in shallow small streams, allowing the identification of ripples and dunes. The present study involved a dedicated field experiment at the Gam stream, which is a tributary of the Nakdong River, South Korea. An unmanned aerial vehicle based hyperspectral image was obtained with a spatial resolution of <10 cm and developed an optimal depth-band ratio rating by densely scattered in situ bathymetry measurements with a portable Real Time Kinematic Global Positioning System. The derived hyperspectral bathymetric map with a 7 cm spatial resolution successfully captured the detailed bed morphology, where dunes with sizes of 1.5 m were clearly identifiable. The correlation with depth measured by RTK-GPS was found to be 0.956, with Root Mean Square Error of 0.033 meter. The research confirmed that the conventional linear OBRA used for low-altitude UAV-based hyperspectral images can capture morphological features in shallow streams with a high spatial resolution. [ABSTRACT FROM AUTHOR]

Scale invariance, which refers to the preservation of geometric properties regardless of observation scale, is a prevalent phenomenon in ecological systems. This concept is closely associated with fractals, and river networks serve as prime examples of fractal systems. Quantifying river network complexity is crucial for unveiling the role of river fractals in riverine ecological dynamics, and researchers have used a metric of "branching probability" to do so. Previous studies showed that this metric reflects the fractal nature of river networks. However, a recent article by Carraro and Altermatt (2022) contradicted this classical observation and concluded that branching probability is "scale dependent." I dispute this claim and argue that their major conclusion is derived merely from their misconception of scale invariance. Their analysis in the original article (fig. 3a) provided evidence that branching probability is scale‐invariant (i.e., branching probability exhibits a power‐law scaling), although the authors erroneously interpreted this result as a sign of scale dependence. In this article, I re‐introduce the definition of scale invariance and show that branching probability meets this definition. This provided an opportunity to address the divergent use of "scale invariance" and "scaling" between fractal theory and ecology. [ABSTRACT FROM AUTHOR]

Land cover changes alter hydrologic (e.g., infiltration-runoff), biochemical (e.g., nutrient loads), and ecological processes (e.g., stream metabolism). We quantified differences in aquatic ecosystem respiration in two contrasting stream reaches from a forested watershed in Colorado (1st-order reach) and an agricultural watershed in Iowa (3rd-order reach). We conducted two rounds of experiments in each of these reaches, featuring four sets of continuous injections of Cl− as a conservative tracer, resazurin as a proxy for aerobic respiration, and one of the following nutrient treatments: (a) N, (b) N + C, (c) N + P, and (d) C + N + P. With those methods providing consistent information about solute transport, stream respiration, and nutrient processing at the same spatiotemporal scales, we sought to address: (1) Are respiration rates correlated with conservative transport metrics in forested or agricultural streams? and (2) Can short-term modifications of stoichiometric conditions (C:N:P ratios) override respiration patterns, or do long-term physicochemical conditions control those patterns? We found greater respiration in the reach located in the forested watershed but no correlations between respiration, discharge, and advective or transient storage timescales. All the experiments conducted in the agricultural stream featured a reaction-limited transformation of resazurin, suggesting the existence of nutrient or carbon limitations on respiration that our short-term nutrient treatments did not remove. In contrast, the forested stream was characterized by nearly balanced transformation and transient storage timescales. We also found that our short-lived nutrient treatments had minimal influence on the significantly different respiration patterns observed between reaches, which are most likely driven by the longer-term and highly contrasting ambient nutrient concentrations at each site. Our experimental results agree with large-scale analyses suggesting greater microbial respiration in headwater streams in the U.S. Western Mountains region than in second-to-third-order streams in the U.S. Temperate Plains region.

Abstract Background Agriculture has greatly influenced water quality, habitats, and fish assemblages in streams of the Mississippi Alluvial Plain (MAP) ecoregion. However, MAP streams have historically been understudied compared to streams in other agricultural regions of the USA. In this study, water quality, habitat, and fish assemblage composition were assessed seasonally (spring, summer, and fall) in eight representative MAP streams located across three U.S. states. The study design included four streams containing highly agricultural watersheds (herein termed “agriculture” streams) and four streams containing mostly forested watersheds (herein termed “forest” streams), which were intended to represent reference conditions for MAP streams. Results In general, forest streams contained significantly better instream and riparian habitats than agriculture streams (P = 0.010–0.040) whereas agriculture streams contained significantly greater levels of primary nutrients (P

Various forest types are distributed in headwater streams. However, differences in diatom assemblages among forest types in Japan have not been thoroughly investigated. The objective of this study was to determine differences in diatom assemblages in the most common forest types in Japanese headwater streams, old-growth broadleaf forest (OBF) and planted coniferous forest (PCF) types, and to identify diatom species that tend to grow in either the OBF or PCF forest types. Diatom abundance differed between the forest types, but the numbers of species, genera and families did not. Nonmetric multidimensional scaling analysis revealed the differences in diatom assemblages in OBF and PCF types and this difference was brought by particularly of some genera such as Gomphonema, Planothidium and Navicula. Differences in diatom assemblages between the two forest types were considered to be a reflection of the different environmental conditions such as light condition and alkalinity, created by the different forest types.

Reservoir formation in a river system changes a lotic environment to more lacustrine conditions, with impacts throughout the ecosystem. In this study, a river reach containing typical salmonid riffle/run habitat was flooded to create a large, deep pool from June to September in each of 3 years. We test the hypothesis that juvenile Atlantic salmon (Salmo salar) with their preference for run/riffle habitats will respond to the transformation to a lentic environment by moving into adjacent lotic environments. Movements of juvenile Atlantic salmon were monitored using a combination of biotelemetry (radio‐ and passive integrated transponder‐tagging) and electrofishing. Results showed that no tracked fish moved away from the created pool habitat. Mass‐specific growth rates showed the created pool habitat resulted in net growth of juveniles. The results confirm that fish may not immediately (i.e., at least for an approximate 2 months) respond to rapid, large‐scale habitat alterations by moving to find similar habitat conditions outside the altered habitat. This is most probably related to plasticity of behavior and habitat use, and no change in biological conditions to a point that would negatively impact fish growth and survival, for example food availability, competition, or predation. The results also support the hypothesis that the relative importance of physical habitat variables is not universal among streams and populations, therefore limiting the value of applying standard habitat suitability criteria and use. [ABSTRACT FROM AUTHOR]

The effect of mixing litter on decomposition has received considerable attention in terrestrial and aquatic (but rarely in both) ecosystems, with a striking lack of consensus in the obtained results. We studied the decomposition of a mixture of poplar and alder in three terrestrial: aquatic exposures to determine (1) if the effect of mixing litter on mass loss, associated decomposers (fungal biomass, sporulation rates, and richness), and detritivores (abundance, biomass, and richness of invertebrate shredders) differs between the stream (fully aquatic exposure) and when litter is exposed to a period of terrestrial exposure prior to immersion and (2) the effect of the mixture across exposure scenarios. The effect of the mixture was additive on mass loss and synergistic on decomposers and detritivores across exposure scenarios. Within scenarios, mass loss and decomposers showed synergistic effects only in the fully aquatic exposure, detritivores showed synergistic effects only when the period of terrestrial was shorter than the period of aquatic exposure, and when the period of terrestrial was equal to the period of aquatic exposure the effect of the mixture was additive on mass loss, decomposers, and detritivores. The species‐specific effects also differed among exposure scenarios. Alder affected poplar only when there was a period of terrestrial exposure, with increased sporulation rates and fungal richness in exposure 25:75, and increased mass loss in exposure 50:50. Poplar affected alder only under fully aquatic exposure, with increased mass loss. In conclusion, the synergistic effects of the mixture changed with a period of terrestrial exposure prior to immersion. These results provide a cross‐boundary perspective on the effect of mixing litter, showing a legacy effect of exposure to terrestrial decomposition on the fate of plant litter in aquatic ecosystems and highlighting the importance of also assessing the effect of mixing litter on the associated biota and not only on mass loss. [ABSTRACT FROM AUTHOR]

In South Korea, the use of hydroponic cultivation has been on the rise. However, this system produces a large amount of wastewater. In this study, the amount of wastewater generated by hydroponic tomato cultivation is identified, and a management plan is proposed. Based on the analysis of 103 tomato HWW samples, it was found that the electrical conductivity (EC) was 4.25 ± 1.01 dS/m, the nitrogen (N) content was 411.21 ± 122.64 mg/L, and the phosphorus (P) content was 47.74 mg/L, which caused eutrophication. Therefore, agricultural reuse and HWW treatment were proposed. Regarding the annual HWW load, 1 ha of hydroponics discharges 964.26 kg/ha of N, 111.95 of P, 937.46 of K, 795.14 of Ca, 313.83 of Mg, and 405.40 of S. The trace elements were heavy metals, which were calculated as Fe—4.03, Mn—0.77, Zn—1.08, B—2.25, Cu—0.38, and Mo—0.05 kg/ha. Since wastewater is a national source of drinking water, it needs to be collected and treated. Inter-item correlation analysis showed that most of the fertilizer components were correlated with the EC concentrations. This study can be used to determine the concentrations required for agricultural reuse and to determine the treatment capacity in HWW management. [ABSTRACT FROM AUTHOR]

The study used remote sensing and GIS techniques for defining the watershed and computing various morphometric characteristics of the Wadi Al-Naft Basins in Diyala Governorate, Iraq. The findings reveal the existence of two sub-basins, each of which was found to have four streams order. The drainage density, a measure of the stream length per unit area, was found to be 0.19 and 0.16 km/km2, respectively. They found 153 streams, categorized into different orders based on size and connectivity. First-order streams were found to be 882.71 km in length, totalling 128, while second-order streams totalling 533.12 km in length. Third-order streams numbered 4 with a total length of 199.9 km, while there were two fourth-order streams with a total length of 57 km. These results may be utilised to examine water flow patterns in the area and are crucial for understanding the hydrological features of the Wadi Al-Naft Basin. To effectively manage water resources, the research underlines the value of GIS in obtaining data on water resources, including a range of morphometric factors. A valuable tool for water resource management, the paper outlines a systematic process for identifying and characterising watersheds that may be used in a case study. [ABSTRACT FROM AUTHOR]

The balance of organic carbon (OC), nitrogen (N) and phosphorus (P) plays a crucial role in determining the processing, retention, and movement of these solutes across the aquatic continuum. Floods and droughts can significantly alter the quantity and ratios of OC:N:P export within inland waters, but how these ratios change, and are coupled within watersheds that integrate rivers and lakes, is not well known. We investigated the stoichiometry and export of dissolved organic carbon (DOC), total N (TN) and total P (TP) in two lake watersheds (10 inflows, 2 outflows) in the southern Boreal Shield over a 37‐year period. Although DOC, TN, and TP concentration behaved similarly, DOC:TN:TP ratios varied seasonally, strongly modulated by stream discharge. DOC:TN, DOC:TP and TN:TP export initially increased rapidly with increasing discharge, peaking at 10%–20% exceedance of the annual discharge for DOC:TP and TN:TP ratios, indicating a rapid depletion of catchment OC sources. Both flood and low flow events resulted in lower DOC:TN and lower DOC:TP export—thereby increasing the relative contributions of stream TN and TP. Consequently, elevated annual discharge coupled with infrequent but high floods and periods of low flow events increased the contributions of TN and TP relative to DOC. Overall, the lakes retained DOC, while increasing TN relative to TP. Nonetheless, the flow regime played a role in modulating nutrient retention in the lakes, likely due to changes in residence time, and the interplay of physical, photochemical, and biological degradation processes. Plain Language Summary: How floods and droughts affect the relationship between organic carbon (OC) and nitrogen and phosphorus in terms of their alteration, removal from, or storage within, river and lake environments is not well known. We investigated two lake watersheds with their 10 inflowing and 2 outflowing streams over 37 years. The ratios of the OC to nutrients changed seasonally and were affected by intra‐annual stream flow variability. Slightly higher than average flows (10%–20% higher) initially increased the amount of OC that was exported from the watershed compared to nitrogen and phosphorus, but this export was notably lower during low flows and floods. This highlights the effects of extremely high and low flows, resulting in increased nitrogen and phosphorus in the streams. Internal processing by lakes generally decreased OC, while adding nitrogen relative to phosphorus, however the lakes retained less OC and phosphorus when the number of annual floods increased. This is important as the frequency and intensity of floods and droughts are predicted to increase in the future which may change how nutrients are altered and removed along the inland‐marine aquatic continuum. These potential changes could impact aquatic ecosystems and the ecosystem services they provide. Key Points: Our long‐term data set provides a robust perspective on patterns in watershed‐scale stoichiometry and organic carbon and nutrient transportFlow regimes (floods and periods of low flow) are critical in shaping nutrient and organic carbon stoichiometry in aquatic ecosystemsLakes play an important role in nutrient and organic carbon removal within a stream network [ABSTRACT FROM AUTHOR]

Background: Agriculture has greatly influenced water quality, habitats, and fish assemblages in streams of the Mississippi Alluvial Plain (MAP) ecoregion. However, MAP streams have historically been understudied compared to streams in other agricultural regions of the USA. In this study, water quality, habitat, and fish assemblage composition were assessed seasonally (spring, summer, and fall) in eight representative MAP streams located across three U.S. states. The study design included four streams containing highly agricultural watersheds (herein termed "agriculture" streams) and four streams containing mostly forested watersheds (herein termed "forest" streams), which were intended to represent reference conditions for MAP streams. Results: In general, forest streams contained significantly better instream and riparian habitats than agriculture streams (P = 0.010–0.040) whereas agriculture streams contained significantly greater levels of primary nutrients (P < 0.001–0.010). Differences between agriculture and forest streams with respect to other physical and chemical variables were intermittent and season dependent. Fish assemblages in agriculture and forest streams were structured primarily along an environmental gradient reflecting instream habitat conditions, water nutrient concentrations, and benthic chlorophyll-a production. Structurally, fish assemblages in both stream types contained many regionally common species, though some species appeared to exhibit affinities for a particular stream type. Functionally, fish assemblages in agriculture streams contained more tolerant species, more omnivores, and fewer insectivores compared to forest stream assemblages, which were nearly all insectivores. Overall, one-third of the fish specimens collected in forest streams classified as intolerant species. Conclusions: Our results suggested that stream water quality, habitat, and fish assemblages differed between agriculture and forest streams in the MAP, with fish assemblages exhibiting both structural and functional differences. Results were consistent with a larger body of literature from smaller, headwater streams whereby land-use changes (e.g., row-crop agriculture) impacted the physical, chemical, and biological characteristics of stream ecosystems. Results further highlight the importance of land use management and its effects on habitat diversity in stream ecosystems, and that protecting the few remaining undisturbed or less-disturbed streams should be a priority. [ABSTRACT FROM AUTHOR]

The macroinvertebrate community, physical–chemical water variables and hydromorphological indices were studied in the Turón River (Málaga, Southern Spain). Our study aims to improve the knowledge of the most influential environmental factors at different spatial and temporal scales in Mediterranean rivers, in order to establish better management of Mediterranean river ecosystems. To this end, in this work, seasonal sampling was carried out for one year to evaluate the effect of the characteristics of the drainage basin (i.e., geology, topography, land use) on the macroinvertebrate community. To this end, the environmental variables of the catchment basins were evaluated at three different scales: (i) watershed level, (ii) valley segment level and (iii) local level. The results showed that 13 environmental variables, 3 at the watershed scale, 5 at the valley segment scale and 5 at the local scale, influenced the macroinvertebrate community. Land use is the main explanatory variable at the watershed scale, while stream channel curvature is the most common variable at the valley segment scale, and the habitat assessment index is the variable with the strongest influence at the local scale. The influence of different spatial scales presented a seasonal variation. During spring, autumn and winter, the watershed scale exhibited the highest resolution (adjusted R2 = 0.20–0.29), while in summer, the local scale became the most significant in explaining the presence of macroinvertebrate taxa (adjusted R2 = 0.17). The obtained results emphasize the significance of temporal and spatial scales in Mediterranean rivers for adequate river ecosystem management. [ABSTRACT FROM AUTHOR]

Studying competitive effects of microbial and light-induced degradation of dissolved organic matter (DOM) is crucially important for understanding the factors controlling aquatic carbon (C) transformation in boreal waters. However, studies addressing both DOM and trace element (TE) behavior are limited, which does not allow assessment of coupled C – TE (including macro- and micronutrients and toxicants) biogeochemical cycles in these environmentally important settings. Here we conducted a seasonally-resolved assessment on the degree of DOM and related major and TE transformation under biotic activity and sunlight using conventional incubations of humic surface waters from the European subarctic. We studied bio- and photodegradation over 2–3 weeks in an ombrotrophic peatbog continuum (subsurface water from piezometer – small peatland pool – outlet stream) during July, and in three horizons (0.5, 5 and 10 m) of deep (30 m), a stratified forest lake from the same region during June, August and September. Along the bog water continuum in July, biodegradation rate was the highest in subsurface waters collected via piezometer and the lowest in the acidic peatland pool (0.17 to 0.03 mg C L-1 d-1, respectively). Photodegradation was similar for piezometrically collected subsurface waters and the stream (about 0.3 mg C L-1 d-1), but was not detectable in the peatland pool. The waters of forest lake exhibited a strong seasonal effect of biodegradation, which was the highest in October and the lowest in June (0.04 and 0.02 mg C L-1 d-1, respectively). The photodegradation of DOM from the forest lake was observed only in June and August (0.19 and 0.07 mg C L-1 d-1, respectively). Biodegradation was capable of removing between 1 and 7 % of initial DOC, being the highest in the forest lake in October and in peatland pool in summer. The photolysis was capable of degrading a much higher proportion of the initial DOC (10–25 %), especially in the forest lake during June and the bog stream during July. The change of optical parameters confirmed the highest photodegradation occurs in June (Arctic summer) and demonstrates a decrease of chromophoric (aromatic) compounds during incubation, whereas biodegradation acted preferentially on aliphatic, low molecular weight compounds. Only a few trace metals were sizably affected by both photo- and biodegradation of DOM (Fe, Al, Ti, Nb and light REE), whereas V, Mn, Co, Cu and Ba were affected solely by biodegradation. Typical values of TE removal over a 2-week period of incubation ranged from 1 to 10 %. These effects were mostly pronounced in the less acidic forest lake compared to the bog waters. A likely mechanism of TE removal was their coprecipitation with coagulating Fe(III) hydroxides. When averaged across sites and seasons, DOM biodegradation and photodegradation processes could remove 5.3 and 10.8 mg C L-1 y-1, respectively. Compared to typical CO2 emissions from inland waters of the region, biodegradation of DOM can provide the totality of C-CO2 evasion from lake water surfaces whereas bio- and photodegradation are not sufficient to explain the observed fluxes in bog water continuum. Overall, these results demonstrated strong spatial and seasonal variability in DOM and TE complexes bio- and photodegradation, which was poorly accessed until now, and call for the need of a systematic assessment of both processes across seasons with high spatial resolution. [ABSTRACT FROM AUTHOR]

The metacommunity theory proposes that community structure and biodiversity are influenced by both local processes (such as environmental filtering) and regional processes (such as dispersal). Despite the extensive use of traditional bioassessments based on species‐environment relationships, the impact of dispersal processes on these assessments has been largely overlooked. This study aims to compare correlations between various bioassessment indices, including Shannon Weiner (H′), Biological Monitoring Working Party (BMWP), average score per taxon (ASPT), biotic index (BI), and EPT taxa index (EPT), based on macroinvertebrates collected from 147 sampling sites in a subtropical Chinese near‐natural catchment. Modified indices were calculated by removing species strongly influenced by dispersal processes to address the influence of dispersal processes. Their relationship with environmental factors was then compared to the original indices. The study employed random forest regression (RFR) to compare the explanatory power of environmental factors using the two sets of indices. The spearman rank correlation analysis was conducted to examine the correlation between indices and environmental factors. The river health assessment was performed based on both modified and original indices. The results reveal significant differences between original and modified indices (especially H′ and BI) providing a more accurate reflection of environmental conditions. Furthermore, the sensitivity of the different indices to various environmental factors varied, leading to differences in the bioassessment results between the modified and the original indices. Notably, original H′, BMWP, and ASPT overestimated the bioassessment results, whereas the original BI underestimated them. These findings offer valuable insights into bioassessment and river health assessment evaluation within the catchment and other interconnected freshwater ecosystems, such as lakes, reservoirs, and wetlands. Our study underscores the importance of assessing and mitigating the impact of dispersal processes on bioassessment to obtain a more precise representation of the status of freshwater ecosystems. [ABSTRACT FROM AUTHOR]

This study aimed to determine the water quality classes of seven rivers in the North Aegean Basin (Türkiye) according to their benthic macroinvertebrate groups. In order to determine water quality levels, water and benthos samples were taken from 17 localities in May and June 2014, and the collected material was examined. As a result, a total of 22,348 benthic macroinvertebrate individuals belonging to 47 taxonomic groups were identified. The main groups and individual numbers were as follows: Chironomidae (8948 ind.), Baetidae (3910 ind.), Oligochaeta (1715 ind.), Gammaridae (1667 ind.), Potamanthidae (1401 ind.), Asellidae (1113 ind.), Melanopsidae (968 ind.), Physidae (618 ind.), Dugesiidae (475 ind.) and Hydropsychidae (107 ind.). The relationships between benthic macroinvertebrates and environmental variables were examined by canonical analysis. The dominance, BMWP (Biological Monitoring Working Party) and ASPT (Average Score Per Taxon) indices among benthic invertebrate groups were calculated. The dominant group was Chironomidae with ~ 40%. Considering the BMWP scores, stations S2, S3, S12 and S17 were classified as polluted, station S5 was classified as unpolluted. ASPT scores indicated that station S3 was heavily polluted and S16 was the cleanest station. [ABSTRACT FROM AUTHOR]

Released antibiotics from source to stream can influence bacterial communities and potentially alter the ecosystem. This research provides a comprehensive examination of the sources, distribution, and bacterial community dynamics associated with varied antibiotic release sources adjacent to the stream. The residual of antibiotics from different sources was determined, and the bacterial community structure was examined to reveal the differences in the bacteria community in the stream. The residual of antibiotics was quantified with liquid chromatography–tandem mass spectrometry (LC-MS/MS), and the Illumina MiSeq platform was utilized to sequence bacterial 16S rRNA genes, providing comprehensive insights into the bacterial community structure in the sediment across five different sites. Results indicated that the presence and distribution of antibiotics were significantly influenced by released sources. In the case of the bacterial community, the Proteobacteria and Firmicutes were the most dominant phyla in the sediment, and especially, the Firmicutes showed higher abundance in sites mostly affected by livestock sources. Additionally, livestock gut bacteria such as Clostridium saudiense, Proteiniclasticum ruminis, and Turicibacter sanguinis were prevalent in antibiotic-contaminated sites adjacent to livestock facilities. Overall, this study provides critical insights into the effect of antibiotic contamination by verifying the relationship between the occurrence of antibiotic residuals and the alteration in the bacterial community in the stream. [ABSTRACT FROM AUTHOR]

Larval lampreys are filter feeders that live for several years burrowed in fine sediments in freshwater streams. Stream side channels and edges, where larval lampreys gather, are vulnerable to natural and human‐caused dewatering. Water level reductions can strand and kill thousands of larval lampreys, in part because many remain burrowed until their habitats are exposed, at which point larvae must emerge and attempt to move over dewatered substrate to locate wetted habitat. Dewatering for restoration efforts or seasonal closures of irrigation canals can be done slowly to reduce lamprey strandings, but in some settings, mechanisms are lacking to control the dewatering rate. Phased dewatering, where water level is reduced in stages separated by periods of static water level, could provide options when dewatering rate cannot be tightly controlled. To guide this phased approach, information is needed on the movement capability of larval lampreys. We examined larval lamprey (Entosphenus tridentatus and Lampetra spp.) movement distance and rate over dewatered substrate at shoreline slopes of 1%, 5%, 10% and 20% in a laboratory setting and modelled results using gamma regression models. Model results suggest both movement distance and movement rate increased with increasing slope and increasing larval length. We used the models to predict minimum distances and rates that 90%, 75% and 50% of medium‐sized (75 mm) lampreys would move over dewatered substrates on slopes of 1%–20%. The models predicted that 50% of larvae could move distances of ≥31 cm at rates of ≥0.7 mm/s on a 1% slope and distances of ≥502 cm at rates of ≥8.6 mm/s on a 20% slope. We present an example scenario of how information on larval movement capabilities and shoreline slope could guide phased dewatering events to limit impacts to lampreys. [ABSTRACT FROM AUTHOR]

Caves represent unique and extreme ecosystems inhabited by specifically adapted and metabolically diverse organisms (phototrophs, heterotrophs, and mixotrophs). Hydrogeologically active river caves, such as Stopić Cave (Serbia), have additional characteristics. Knowledge is lacking on the cyanobacteria and algae living in these specific ecosystems and, in particular, in the water bodies within caves. The main objectives of this study were to investigate the diversity, composition, and seasonality of cyanobacterial and algal communities of the Trnavski stream flowing through Stopić Cave and to assess water quality. Initial analysis of planktonic and benthic samples collected during the winter, spring, and summer of 2020 from six sites along the Trnavski stream flowing through Stopić Cave identified 132 cyanobacterial and algal taxa. Subsequent detailed analysis of benthic diatoms increased the total number of identified taxa to 242, with representatives of Bacillariophyta, Cyanobacteria, and Chlorophyta being the most common. Representatives of Xanthophyceae, Chrysophyceae, Euglenophyceae, Dinophyceae, and Cryptophyceae were also recorded. The highest total number of taxa was found in the spring (n = 156), and the lowest number in the summer (n = 60). Many taxa were specific to only one season, with the majority of these belonging to Cyanobacteria and Chlorophyta. The values recorded for pH, conductivity, and light intensity showed that there was relatively little seasonal variation; in contrast, water temperature varied greatly among seasons. According to most diatom indices, the water quality of Trnavski stream was good at most sampling sites during the study period. [ABSTRACT FROM AUTHOR]

Present research article deals with fish faunal diversity and their conservation status in Maseh and Khairan streams of Beas River in Kangra district of Himachal Pradesh. Ten fish species were recorded from the streams. Out of which, 6 species viz., Pethia ticto, P. conchonius, Opsarius bendelisis, Mastacembelus armatus, Salmostoma bacaila were common in both the streams, whereas, Barilius vagra was present in Maseh stream and Xenontodon cancila, Crossocheilus latius diplocheilus and Acanthocobitis botia were present in Khairan stream only. All the fish species belongs to Least Concern category as per IUCN. These streams provide refuge to large number of indigenous fish population, but are also undergoing major habitat alterations due to various man-made stressors. So proper conservation of diversity of the region is necessary before it is vanished. [ABSTRACT FROM AUTHOR]

Concerning the impact of organic contamination, most studies focus on the main river courses, which are affected by large wastewater plants and intensively urbanized areas, while a large part of a river's catchment area is made up of small streams flowing through rural or forested areas. As a result, the impact of even small sources of organic load on small systems is often not analysed. This study investigated the impact of a small sewage source on the aquatic environment of the Caramagna Creek (NW Italy). At the study site, the creek receives an effluent sewer from a small cluster of houses. To evaluate the impact of this point source of pollution, we estimated macroinvertebrate community composition and abundance monthly from January 2005 to March 2006 in two stations, located respectively 50 m upstream and 50 m downstream of the sewer pipe. At the same time, main physicochemical parameters, microbiological data, and chlorophyll-a concentration were assessed. These data aim to inspire additional research, particularly in addressing the implications of often overlooked small impacts occurring in small rivers, which can have an enormous impact given the dendritic organisation of the hydrographic network and the multiplicative effect along the river system. These results are especially relevant in the context of evolving river dynamics influenced by decreasing flows, resulting in a diminution in dilution capacity and thus greater fragility of river ecosystems.Moreover, if we consider only the upstream site, this dataset holds important potential related to non-impacted macroinvertebrate communities, constituting an important reference because it integrates macroinvertebrate community data with different environmental data, from granulometry to in-stream productivity, from chemical-physical to microbiological data.

The vertical connectivity of the river aquatic ecosystem was evaluated based on fish and artificial structures in Dorim stream, an urban stream in Seoul. As a result of a survey in the downstream area in 100.0 m of a total of 71 artificial structures, 13,728 individuals of fishes belonging to five orders, seven families, and 25 species were investigated, with the dominant species Zacco platypus and the subdominant species Rhynchocypris oxycephalus. As for endemic species, seven species were investigated and in terms of feeding characteristics, omnivorous species were the most common with 17 species (68%). Also an alien species, Poecilia reticulata was found. Fish species tended to decrease as the survey was conducted to upstream. Based on the movement characteristics of the fish species and the features of artificial structure survey results, the longitudinal continuity of each artificial structure was evaluated as 43 continuity, two damaged, 19 discontinuity, and seven absent. In inclined structures, stream velocity was found to be the main factor for discontinuity. In vertical structures, the down depth and head drop appeared to be the main factors for discontinuity. The results of this survey are expected to serve as basic data for the conservation of river aquatic ecosystems in the future.

Spatial and temporal variations of the water table could be explained by the one-dimensional Boussinesq equation by incorporating the variables of evapotranspiration and groundwater recharge with appropriate initial and boundary conditions. In this study, the stream–aquifer interaction has been investigated through a numerical example model with the implementations of Galerkin's method-based Finite Element Solution (FES), Hybrid Finite Analytic Solution (HFAS), Fully Implicit Finite Difference Solution (FIFDS) of one-dimensional nonlinear Boussinesq equation, and analytical solutions of the Boussinesq equation linearized by Baumann's transformation (AS I) as well as linearized by Werner's transformation (AS II). Considering HFAS as the benchmark solution, it was observed that in both recharging and discharging aquifers, water table profiles at 1 day and 5 days as obtained from FES followed by FIFDS were observed quite close to HFAS. Based on L2 and Tchebycheff norms, FES and FIFDS were ranked in first and second place, respectively. L2 and Tchebycheff norms could not consistently establish the performance ranking of analytical solutions but their performance ranking was certainly below the numerical solutions. The performance ranking of analytical solutions could not consistently be established using the L2 and Tchebycheff norms, but it was certainly below the numerical solutions. HIGHLIGHTS One-dimensional Boussinesq equation after incorporating constant SI and ET was found appropriate to signify stream–aquifer interaction in the semi-infinite flow region.; Both recharging and discharging aquifers, water table profiles at 1 day and 5 days as obtained from FES followed by FIFDS were observed quite close to HFAS.; Performance of AS I was better than AS II in both recharging and discharging aquifers.;

AbstractDissolved organic carbon (DOC) in soils is released into streams, working as a main component of the carbon cycle. DOC in terrestrial and aquatic ecosystems participates in many biogeochemical reactions and processes such as heterotrophic respiration, sorption of metals, and transport of pollutants. In order to understand the connectivity of organic carbon among soil, soil water, and forest streams, we investigated the concentrations and dual carbon isotope ratios (δ13C and Δ14C) of soil organic carbon (SOC) and water-extractable organic carbon (WEOC) obtained from soils beneath two tree species stands, and compared these with stream Δ14C-DOC of the forest watershed. Soil samples were collected at different depths (0–10, 10–30, and 30–50 cm) beneath Japanese cedar (Cryptomeria japonica) and sawtooth oak (Quercus acutissima). Although the SOC concentration was not significantly different between the two tree species, the WEOC concentration ([WEOC]) of soil at 0–10 cm depth under Cryptomeria japonica was higher than that of Quercus acutissima, in general. The δ13C-SOC and δ13C-WEOC increased, while the Δ14C-SOC and Δ14C-WEOC decreased with increasing soil depth. The Δ14C-WEOC was higher than the Δ14C-SOC, indicating that WEOC could be primarily derived from the young, hydrophilic, and exchangeable fraction of SOC, rather than from SOC strongly bonded to mineral soils. However, the stream Δ14C-DOC was lower than Δ14C-WEOC in general, except during summer storms. The 14C-depleted DOC released from deep soils or groundwater might lower Δ14C-DOC of a stream, suggesting that relatively old DOC could be released into streams during baseflow. This is contrary to the results of previous studies that have reported positive stream Δ14C-DOC from temperate forests. The discrepancy warrants future research on forest stream Δ14C-DOC across entire seasons, particularly under Asian monsoon climates.