Phytoplankton communities typically comprise a few dominant species and numerous rare ones, but their responses to seasonal precipitation changes remain poorly understood. To address this knowledge gap, investigations were conducted on the environmental conditions and phytoplankton communities in the Lalin River Basin during the dry and rainy seasons. Structural equation modeling and co-occurrence network analysis were then utilized to explore the assembly processes of dominant and rare phytoplankton communities following a seasonal heavy rainfall event. Our results showed seasonal heavy rainfall events significantly altered the phytoplankton community composition and rare phytoplankton diversity (p < 0.05). Furthermore, the stochastic process was particularly pronounced for rare species (i.e., 4.44%, p < 0.01). Co-occurrence network analysis revealed that increasing precipitation enhances the complexity and stability of phytoplankton ecological networks. Additionally, the relative importance of dominant species decreases, while that of rare species increases. This phenomenon can be described as the seasonal heavy precipitation weakening the so-called “Matthew effect” in the ecosystem. In summary, our results shed light on the phytoplankton ecology of agricultural rivers and reveal how changes in precipitation influence the formation of phytoplankton sub-communities and the structure of their networks.

Stream ecosystems have been impacted by multiple anthropogenic stressors including the loss of riparian canopy cover. However, it remains unclear how these stressors shape the profiles and transfer of fatty acids in basal resources, and subsequently affect the trophic linkages in stream food webs. We collected 158 food web samples including three basal resources (periphyton, fine benthic organic matter (FBOM) and seston), two primary consumers (macroinvertebrate and omnivorous fish), and one secondary consumer (carnivorous fish) together with water quality samples across an anthropogenic disturbance gradient in a small catchment (Laoguan River) of the Yangtze River, China. We investigated the influence of riparian land-use changes, canopy cover and water quality on the nutritional quality indicated by the proportions of eicosapentaenoic acid (EPA) in periphyton, seston and FBOM and their transfer in stream food webs. Our results showed that land use primarily affected the reduced the proportions of EPA in periphyton more than seston and FBOM. It was confirmed that loss of canopy coverage reduced the proportions of EPA of periphyton due to the significant correlations and difference between two groups: the least disturbed group (forest > 90 %) and the highly disturbed group (high agriculture/urban). Compared to the least-disturbed sites, food webs appeared to be simpler with less trophic linkages at highly disturbed sites affected by agricultural and urban land uses. Finally, we validated that EPA was the important linkage between periphyton and primary consumers-macroinvertebrates, and further second consumers- omnivore fish, which may account for the decrease of network of trophic links at highly disturbed sites. This study provides insights into how anthropogenic stressors, particularly land-use changes and loss of riparian canopy cover, affect the nutritional quality of basal resources and simplify food web structures in stream ecosystems, highlighting the critical role of eicosapentaenoic acid (EPA) in linking trophic levels.

Periphyton, which is rich in polyunsaturated fatty acids (PUFA), serves as an indispensable high-quality basal resource for consumers in stream food webs. However, with global warming, how fatty acid composition of periphyton changes and consequent effects on their transfer to higher trophic level consumers remain unclear. By carrying out a manipulative mesocosm experiment with a 4°C increase, warming led to a significant decrease in the proportions of PUFA and Long-chain PUFA (LC-PUFA, >20 C) in periphyton from 13.32% to 9.90% and from 3.05% to 2.18%, respectively. The proportions of three PUFAs-α-linolenic acid (18:3ω3), arachidonic acid (ARA, 20:4ω6), and docosahexaenoic acid (22:6ω3)-also declined significantly (P < .05). Notably, the fatty acid profile of the consumer-Bellamya aeruginosa reflected the changes in basal resources, with a decrease in PUFA from 40.14% to 36.27%, and a significant decrease in LC-PUFA from 34.58% to 30.11%. Although algal community composition in biofilms did not significantly change with warming, significant transcriptomic alterations were observed, with most differentially expressed genes related to fatty acid synthesis in lipid metabolism and photosynthesis down-regulated. Our findings indicate that warming may hinder the production and transfer of high-quality carbon evaluated by LC-PUFA to consumers, consequently affect the complexity and stability of stream food webs.

Delicata is a genus of globally distributed, freshwater cymbelloid diatoms. We analysed the variability of valve morphology across species of the genus from China, New Caledonia, Central Europe and southwest Russia. The analysis focused on key distinctive features of Delicata: the arrangement and structure of striae, morphology of apical areolae and presence or absence of stigmata. As a result, we have re-evaluated the importance of ultrastructural valve characters for taxonomy and phylogeny of Delicata and proposed a new term 'apical stria cluster' to name the apical areolae in certain species of Delicata. We also discussed the structure of isolated pores - parastigmata - in the genus. In addition, a new species of genus, Delicata zhangii sp. nov. was discovered in Shaanxi and Hubei provinces, China. The new species is hereby described on the basis of unique combination of valve features - lunar-lanceolate outlines with barely protracted apices, linear striation, presence, structure of stigmata and areolae. Comparisons are made amongst the species of the genus within the framework of the morphological analysis.

Ultraviolet radiation (UVR) exposure increased in the past due to stratospheric ozone depletion, raising concerns about its long-lasting effects on freshwater ecosystems. While the ozone layer is gradually recovering, the effects of UVR on nutritional quality of periphyton as energy base for organisms in higher trophic levels in streams have not been understood. We conducted a manipulative experiment in mesocosm with four treatments (ambient, UVA, UVB, and combined UVA and UVB) to study the effects of UVR on nutritional quality of periphyton including oganic nutrient (long-chain polyunsaturated fatty acids, LC-PUFAs) and inorganic nutrient (P:C ratio) which both are nutritional quality biomarkers. UVR treatments significantly reduced periphyton nutritional quality represented by decreased LC-PUFAs i.e. eicosapentaenoic acid (EPA) under UVA, UVB, and UVAB treatments, while UVB and UVAB treatments resulted in the deficiency in phosphorus (P) in basal resources by a significant decrease in the P:C ratio. Specifically, LC-PUFAs decreased by approximately 40-50 % (from 5.20 % in the ambient to 2.61-3.20 %), and the P:C ratio decreased 2-3-fold (from 0.048 to 0.018-0.024) under UVR treatments. We found these the decrease of LC-PUFAs was linked to "shifts" of species in community, including a succession from Bacillariophyta to Chlorophytes and Cyanobacteria. It was revealed that UVR down regulated key enzymes in fatty acid biosynthesis and elongation, such as acetyl-CoA carboxylase (ACCase), 3-ketoacyl-CoA synthase (KCS), and omega-3 fatty acid desaturase (FAD3) associated with unsaturated fatty acid synthesis using transcriptomic analysis. These findings demonstrated that UVR exposure reduces the nutritional quality of periphyton as basal resources in stream food webs through community succession and down regulated genes encoding key enzymes.

Periphyton acts as an important primary producer in stream food webs with bottom-up grazing pressure and is also subject to effects of top-down grazing pressure. However, the underlying mechanisms of these interactions remain unclear. In this study we conducted a mesocosm experiment to explore the periphyton response to grazing pressure by the freshwater snail Bellamya aeruginosa in relation to food quality indicated by polyunsaturated fatty acid (PUFA) biomarkers, including eicosapentaenoic acid (20:5n3) and the 22C fatty acid docosahexaenoic acid (22:6n3), which are essential for cell growth and reproduction and cannot be synthesized by most consumers of periphyton. Results indicated that periphyton grazing pressure led to a decrease in Bacillariophyta, which contain high-quality PUFAs such as eicsapentaenoic acid and docosahexaenoic acid, and an increase in Cyanophyta and Chlorophyta, which are rich in 18C PUFAs such as linoleic acid (18:2n6) and alpha-linolenic acid (18:3n3). We observed upregulation of genes that participate in lipid metabolism promoting unsaturated fatty acid biosynthesis, alpha-linolenic acid metabolism, and glycerophospholipid metabolism, which are related to the carbohydrate and energy metabolism maintaining the energy stability of periphyton. These results demonstrate that the food quality of periphyton decreased under grazing pressure and also elucidate the compositional, chemical, and molecular perspectives of the interactive bottom-up and top-down effects on structuring stream food webs.

Dissolved inorganic carbon (DIC) provides a substrate for primary production in the lotic ecosystems, yet carbon's biogeochemical origination in the lotic food webs is still poorly constrained. Here, we assembled a global dataset of isotopic composition (i.e., 13C/12C or δ13C) of DIC and periphyton (algae being the primary producers) in river waters, and carried out a field study in two catchments respectively with carbonate and silicate dominated lithologies on the Tibetan Plateau. A two-endmember mixing model based on the datasets indicated that δ13C and concentrations of DIC in the river waters were largely determined by the catchment-scale chemical weathering of different lithologies. Meanwhile, a significant correlation was obtained between δ13C-DIC and δ13C-periphyton in the datasets, strongly implying that the origination of periphyton carbon was largely regulated by the catchment lithologies. The δ13C-periphyton compositions are also affected by isotopic fractionations during algal primary production, which, in turn, were closely related to the relationships between primary productivity and DIC availability in the rivers. The study advances our understanding of the origination and transfer of carbon biogeochemically bridging the geosphere and biosphere in the lotic ecosystems.

Fluvial sediments are one of the hotspots for river nitrogen removal and denitrification is usually considered the main process of nitrogen removal. The availability of nitrogen in headwater rivers is often a limiting factor for sediment denitrification. However, with the increase of N load caused by human activities, we hypothesized that carbon sources might become a key factor controlling the denitrification of sediments in headwater rivers. Here, we measured the denitrification rate using the acetylene inhibition technique and related environmental factors, including both water and sediment features, throughout a year in a subtropical eutrophic river (1st-3rd order streams). The results of our Pearson correlation and multiple regression analyses supported our hypothesis. We found that C sources had a higher explanatory power than N sources, and sediment total carbon (STC) had the greatest influence on the denitrification rate among the different C sources, and that water carbon sources directly affected the sediment denitrification rates according to a structural equation model (SEM). A degraded river reach was selected for revegetation as part of our study, and we found that revegetation increased water DOC from 19.47 mg l- 1 to 24.45 mg l- 1, reduced water NO3- -N from 0.61 mg l- 1 to 0.35 mg l- 1, and significantly increased the sediment denitrification rates by an average of 176%. Our study provides direct evidence that revegetation improves organic carbon limitation in sediment denitrification in a eutrophic headwater river.

Biofilms are considered a basal resource with high nutritional quality in stream food webs, as periphytic algae are abundant of polyunsaturated fatty acids (PUFAs). PUFAs are essential for growth and reproduction of consumers who cannot or have very limited capacity to biosynthesize. Yet, how the nutritional quality based on PUFA of basal food sources changes with light intensity remains unclear. We conducted a manipulative experiment in mesocosms to explore the response and mechanisms of nutritional quality to shading, simulating riparian restoration. We found a significant increase in PUFA% (including arachidonic acid, ARA) under shading conditions. The increased PUFA is caused by the algal community succession from Cyanobacteria and Chlorophyta to Bacillariophyta which is abundant of PUFA (especially eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA). On the other hand, shading increased PUFA via upregulating enzymes such as Δ12 desaturase (FAD2, EC:1.14.19.6) and 3-ketoacyl-CoA synthase (KCS, EC:2.3.1.199) in the biosynthesis of unsaturated fatty acid elongation pathways. Our findings imply that riparian reforestation by decreasing light intensity increases the nutritional quality of basal resources in streams, which may enhance transfer of good quality carbon to consumers in higher trophic levels through bottom-up effects.

Maintaining an optimal eco-environment is important for sustainable regional development. However, existing methods are inadequate for examining both spatial and temporal dimensions. Here, we propose a systematic procedure for spatiotemporal examination of the eco-environment using the space-time cube (STC) model and describe a preliminary investigation of the coupling relationships between basin ecological quality and water eutrophication in upstream of the Han River basin between 2000 and 2020. The STC model considers the temporal dimension as the third dimension in calculations. We first categorized the basin into three sub-watershed types: forest, cultivated land, and artificial surface. Subsequently, the ecological quality and driving factors were assessed and identified using the remote sensing ecological index (RSEI) and Geodetector method, respectively. The findings indicated that the forest basin and artificial surface basin had the highest and lowest ecological quality, respectively. The spatiotemporal cold spots of ecological quality during the past 20 years were mostly located in the vicinity of reservoirs, rivers, and artificial surface areas. Human activity, precipitation, and the percentage of cultivated land were other important driving factors in the artificial surface, forest, and cultivated land sub-watersheds, respectively, in addition to the dominant factors of elevation and temperature. The results also indicated that when the ecological quality degraded to a certain extent, water eutrophication was significantly coupled with the ecological quality of the catchments. The findings of this study are useful for ecological restoration and sustainable river basin development.

As predators are generally larger than their prey, positive body size and trophic position relationships are typically assumed, and these relationships have helped in estimating and predicting the effects of global environmental change on the trophic dynamics of aquatic ecosystems. However, current efforts to confirm the generality of body size-trophic position relationships have focused mainly on interspecific patterns using species-aggregated and averaged data, and little effort has been devoted to assessing how trophic position scales with body size at the intraspecific and community levels as well as exploring its ecological drivers, particularly for fishes in freshwater ecosystems. To fill this gap, we present a broad-scale study of body size-trophic position relationships in freshwater ecosystems at both the intraspecific and community levels using an individual-based body size and isotopic signature dataset that includes 2564 samples of 65 fish species in China. Our results indicate that body size-trophic position patterns at both the intraspecific and community levels can be positive, negative or insignificant. Non-significant patterns predominated at both levels, with slightly more than 30 % showing positive relationships, which highlights that the positive body size-trophic position pattern is not universally prevalent and that body size should be used with caution as a proxy for the trophic position of fishes at both the intraspecific and community levels in freshwater ecosystems. No factor was related to body size-trophic position patterns at the community level, while habitat type, elevation, temperature and fishing pressure were identified as the key determinants of body size-trophic position patterns at the intraspecific level, implying that fishing and climate warming can shift the food-web size structure of freshwater ecosystems by affecting population trophic dynamics.

Riparian deforestation, which leads to increase in light intensity and excessive nutrient loading in waterways, are two pervasive environmental stressors in the stream ecosystems. Both have been found to alter basal resource availability and consequently stream food webs. However, their interactive effects on trophic structure in stream food webs are unclear. Here, we manipulated light intensity and nutrient availability in three headwater streams to evaluate their effects on consumer diet composition and food web characteristics (i.e., trophic diversity and redundancy) with stable isotope analysis. Dietary analysis revealed that the relative contribution of stream periphyton to the diets of macroinvertebrates increased, while that of allochthonous resources, specifically leaf litter from the terrestrial ecosystems in the catchment, decreased in response to open canopy and nutrient enrichment in the streams. The trophic diversity also increased with the elevated light intensity and nutrient availability, while the trophic redundancy decreased, suggesting a reduced ability of the stream ecosystems to resist environmental changes. Nutrient enrichment also increased the δ15N ratios of periphyton and macroinvertebrates, indicating potential δ15N enrichment of stream benthos by nitrogen pollution. Our results suggested that an increase in light intensity due to riparian canopy openness and stream water nutrient enrichment primarily from human activities have interactive effects on resource flow and trophic structure in stream food webs.

Climate, topography, and landscape patterns affect river water quality through processes that influence non-point source pollution. However, little is known about the response of the water quality of rivers on China's Tibetan Plateau to these environmental factors. Based on the water quality parameters data of the Xoirong River on the Tibetan Plateau in western China, the redundancy analysis and variation partitioning analysis were adopted to determine the main influencing factors affecting river water quality and their spatial scale effects. The major water pollutants were further analyzed using the partial least square-structural equation modeling (PLS-SEM). Another mountainous river with a similar latitude, the same stream order, and low anthropogenic disturbance in central China, the Jinshui River, was also selected for comparative discussion. The results indicated that the overall river water quality on the Tibetan Plateau was superior to that of the Jinshui River. At the catchment scale, the cumulative explanatory powers of the influencing factors of both rivers were greatest. Landscape composition and configuration were the determinant factors for the overall water quality of the two rivers, while the river on the Tibetan Plateau was also significantly affected by climatic and topographical factors. Regarding the main water quality issue, i.e., total nitrogen, agricultural production activities might be the main cause of the river on the Tibetan Plateau. This study unveiled that the river water quality on the Tibetan Plateau is sensitive to climate and topography through comparative studies.

The disturbance of reactive nitrogen (N) on ecosystems and biogeochemical cycles is now one of the most severe environmental problems worldwide. Nitrate (NO3-) is usually a dominant reactive N species in river ecosystems. Excessive NO3- concentrations in rivers have led to eutrophication and consequent ecological and environmental damages. Quantifying catchment-scale NO3- yield and export dynamics is crucial for effective remediation of river NO3- pollution. Frequently, natural abundance isotopes of NO3- in a river (δ15N/δ18O-NO3-) are applied to identify sources and potential transformations of NO3- at a catchment scale, while microbial molecular techniques and 15N pairing experiments are employed to reveal the NO3- production and removal processes and their underlying mechanisms in microenvironments (e.g., sediments and soils). In this study, we developed a novel protocol that couples these complementary geochemical and molecular techniques to quantify catchment-scale NO3- yield and fluvial export dynamics. The protocol links microscopic processes with catchment-scale geochemical characteristics to explicitly describe the NO3- cycling processes and their underlying abiotic and biotic mechanisms within a catchment. We applied the protocol to the Dadu and Jiazela catchments on the Qinghai-Tibet Plateau, and demonstrated the effectiveness of the protocol in determining NO3- yield and export dynamics in the catchments.

Benthic metabolism is an essential process which plays a critical role in the carbon and nutrient cycles and in the transfer of material and energy in stream ecosystems. Benthic algae are one of principal primary producers in stream food webs that converts dissolved inorganic carbon to organic matter, and algae are more palatable basal resources for aquatic consumers due to its higher unsaturated fatty acid content than terrestrial carbon. Despite the importance of algae, few studies have investigated how the benthic metabolism is influenced by distal factors, such as upland land use and landscape configuration, and proximal factors, such as stream temperature, nutrient availability, and light availability at various spatial scales. Here, we measured the benthic metabolism and proximal factors at the outlet of 14 selected sub-catchments in a subtropical river. Land use and landscape metrics at the catchment, riparian, and reach scales were processed as distal factors. Using stepwise regression models, we found that the proximal factors, such as water temperature (WT) and total phosphorus (TP), significantly increased primary production, and that nitrate-nitrogen (NO3--N), pH, and electrical conductivity (EC) decreased gross primary production (GPP). Also, TP was positively correlated with respiration (R) while NO3--N negatively impacted R. Structural equation modeling demonstrated that the patch cohesion index negatively affected GPP by restraining WT and TP at the catchment scale while the increased shape index elevated the WT and TP to promote GPP. Our results suggested that stream metabolism is vulnerable to anthropogenic disturbances, such as upland land use and landscape patterns. Thus, land use planning and administration, particularly at catchment scale, should consider how to minimize the influence of human activities on ecosystem function in streams.

Phytoplankton is a crucial primary producer in wetland ecosystems and is highly sensitive to changes in water quality. It has long been considered one of the most important biological indicators for monitoring water pollution. However, our understanding of the various aspects of phytoplankton communities assembly and the factors driving them remains limited. In this study, we conducted collection and analysis of phytoplankton samples from a temperate wetland cluster encompassing both lake and marsh types under the backdrop of industrial pollution from the petroleum industry. Our aim was to investigate the influence of spatial factors, land use patterns, and local environmental variables on the taxonomic and functional structure of the phytoplankton community, utilizing structural equation modeling (SEM) and variation partitioning. Our results revealed that environmental filtering exerts a greater relative impact on shaping the taxonomic composition of phytoplankton compared to mass effects. Human activities, such as industrial and agricultural production, can lead to landscape modifications that increase water nutrient levels and consequently influence the community composition. Taxonomic beta diversity is determined by both mass effects and environmental filtering. In contrast, functional beta diversity responds more to local environmental gradients, while the land use pattern was not important for facets of beta diversity in the wetland cluster. These results validate the concordance and complementarity between functional and taxonomy-based biome structures, highlighting the significance of integrating multiple ecological drivers. The results of this study contribute to a deeper understanding of wetland community assembly and the processes of biogeography, and are of crucial significance for the biological monitoring and management of freshwater ecosystem environmental pollution.

Eutrophication induced by excessive inputs of nutrient is one of the main stressors in aquatic ecosystems. Deforestation in riparian zones alter riparian shading, which together with eutrophication is expected to exert a complex control over stream food webs. We manipulated two levels of riparian shading (open canopy vs. shading canopy) and nutrient supply (ambient vs. nutrient addition) in three headwater streams to investigate the individual and combined effects of eutrophication and loss of riparian shading on carbon sources and nutritional quality of biofilms, and the subsequent trophic effects on macroinvertebrate grazers. Nutrient enrichment increased the autochthonous carbon (i.e., algae especially diatoms) indicated by fatty acid (FA) biomarkers within biofilms and grazers. The nutritional quality indicated by eicosapentaenoic acid (EPA) content of biofilms was increased with nutrient enrichment and more so with the combined effect of an increase in riparian shading, consequently leading to an increase in the nutritional quality, density, and biomass of grazers. In particular, the trophic linkages between biofilms and grazers were mainly influenced by EPA concentration in the biofilms, and strengthened with the combined effects of riparian shading and additional nutrients. Our study emphasizes the nutritional significance of EPA for consumers at higher trophic levels and proposes its potential as an indicator for monitoring the health of aquatic ecosystems.

Changes in stream biodiversity are now mainly driven by land-use development. However, a literature review on the impact of land use on stream macroinvertebrates is lacking, especially a scientometric review. Here, we bibliometrically analyzed the literature on land use and stream macroinvertebrates that were published in 2010–2021 and listed in the Web of Science database. We found that the impact of land use on stream macroinvertebrates had been increasingly studied and that these studies were distributed across the globe and had multi-national collaborations. Through co-citation analysis and high-frequency keyword analysis, we found that land use and some environmental factors, especially water quality and habitat, affected macroinvertebrate community biodiversity, biotic integrity, and patterns. Macroinvertebrate traits, analytical methods or models, evaluation index development, and riparian vegetation were the research hotspots. Using historical direct citation network analysis, we also found that the analytical methods in this field and the macroinvertebrate evaluation index had clear development trends from 2010 to 2021. Our findings can help researchers quickly grasp the background of the impact of land use on stream macroinvertebrates and inform future research.

Biochemical fatty acids (FAs) in vivo are essential to the growth and reproduction of animals including macroinvertebrates in streams and are subject to ambient abiotic variables. However, the main abiotic drivers of FA composition in macroinvertebrate scrapers are varying and uncertain. The aim of this research was to quantify the contributions of abiotic variables, including stream physical, chemical, and climatic variables, to the variation of FAs of macroinvertebrate functional feeding group-scrapers (e.g., Bellamya aeruginosa, Radix swinhoe, Heptagenia sp., and Stenelmis sp.). Stream physical, chemical, and climatic variables and the FAs of scrapers were measured in six subtropical streams during spring. The principal component analysis (PCA) indicated the parameters responsible for FA variation were mainly related to polyunsaturated fatty acids (PUFAs), saturated fatty acids (SAFAs), ω3 PUFA, and ω6 PUFA. Multiple factor analysis (MFA) showed that the FA profiles of scrapers strongly correlated with the physical variables. Specifically, the correlation analysis showed that PUFA and terrestrial FA were significantly positively associated with canopy cover, and in contrast that SAFA was negatively correlated with canopy cover. Although water quality and climate variables did not have a good relationship with FAs, they had a strong correlation with physical variables. This research suggested that the influence of environmental variables (e.g., stream physical, chemical, and climatic variables) on FAs of macroinvertebrate scrapers has complex paths. This study provides a theoretical basis for stream management and an empirical framework for the construction of an interactive network beyond food webs that includes environmental variables.

Land use in uplands is an important factor affecting water quality in its respective catchment, and its influences at the different spatial scales and configurations warrant further investigation. Here, we selected 26 catchments in the upper Han River (China) and sampled the surface water at the outlet of each catchment in four seasons during 2019. Multivariate statistics were used to identify the relationships between land use characteristics in uplands and water quality in river system. The results indicated that chemical oxygen demand (CODMn); pH; dissolved oxygen; electrical conductivity; nutrient, i.e., NH4+-N, NO3--N; and dissolved phosphorus (DP) in rivers displayed significant seasonal variations. Stepwise regression revealed that landscape metrics such as patch density, landscape shape index, and splitting index were important factors influencing water quality in rivers regardless of their spatiality and seasonality. Urban was the most frequently chosen land-use type in the best prediction models, and forest area showed a negative correlation with water quality parameters in most cases for example, DP. Overall, the influence of land use on river water quality was slightly stronger at reach scale than at catchment and riparian scales. Also, nutrients (i.e., NH4+-N, NO3--N, and DP) in rivers were primarily impacted by the land use characteristic at catchment and riparian scales. Our results suggested that multi-scale explorations would help to achieve a fully understanding on the impacts of land use on river water quality.