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Water, energy, food, and ecology are essential for achieving sustainable development in a region, and in order to achieve the Sustainable Development Goals, their security is also essential at a river basin scale. This study investigated the interrelationships among the water system, food system, energy system, and ecosystem in China's Upper Han River, in alignment with Goals 2, 6, 7, and 15 of the United Nations' Sustainable Development Goals (SDGs). To evaluate the achievement of the SDGs in the Upper Han River, this water–energy–food–ecology system was evaluated by a thorough evaluation index system according to Goals 2, 6, 7, and 15, and the weights of the indices were given using a combination of the CRITIC weighting method and entropy approach. The level of coupling coordination of the system from 2000 to 2021 was quantitatively evaluated by using a coupling coordination degree model. The autoregressive integrated moving average model was built to forecast the process of the indices from 2022 to 2041, and the predicted processes of the system were evaluated by the coupling coordination degree model. The degree of coupling coordination improved from 0.396 to 0.845, and the comprehensive assessment development index increased by 113% from 2000 to 2021, demonstrating that it was a stable development period in general. The fragile support capacity of the water system for the energy system, food system, and ecosystem had a great impact on the overall comprehensive evaluation index. SDG2 (food system), SDG6 (water system), SDG7 (energy system), and SDG15 (ecosystem) all have higher levels of internal conflict. These bi-directional dynamics tended to converge in the sufficiency development mode in the future period as well as the historical period. The analysis of the relationship showed that there were inherent connections and interactions between the four goals, as presented by the high level of coupling that persisted between SDG2, SDG6, SDG7, and SDG15. In the process of promoting the achievement of these goals, the coupling degree also tends to be coordinated from 2022 to 2041. The results offer a view for the river basin's sustainable development and management. [ABSTRACT FROM AUTHOR]

Zooplankton play a key role in freshwater ecosystems; however, their community succession and responses to environmental stress remain poorly understood. To fill this gap, zooplankton community dynamics in the main stream, five tributaries and three reservoirs of the Yanhe River Basin (China) were studied in spring and autumn at the zooplankton functional group (ZFG) level. Principal component analysis and non-metric multidimensional scaling were used to reveal the spatiotemporal characteristics of aquatic environmental and zooplankton community structure (ZCS), respectively. Subsequently, redundancy analysis and niche measures were conducted to explore the effects of environmental factors and biotic interactions on ZCS. Significant spatiotemporal heterogeneity in both aquatic environment and ZCS were found. Turbidity, total nitrogen, nitrite-nitrogen, chemical oxygen demand, pH, water depth, water temperature, and chlorophyll a emerged as primary environmental drivers of ZCS. Regarding biotic interactions, weak competition in spring contributed to the positive community succession, while in autumn, intense competition and predation between ZFGs, along with elimination of vulnerable groups, led to community instability. Niche processes emerged as significant shaping factors in the Yanhe River Basin' ZCS. Our study provides valuable insights into zooplankton community response to environmental changes and offers potential applications for understanding other aquatic organisms and ecosystems. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) is the most active organic component in terrestrial ecosystems. In this study, 165 soil samples which were dominated by moss were collected from grasslands with similar vegetation in urban residential areas from 55 cities across different climatic zones of China. The water extractable organic matter (WEOM) of samples was analyzed. The results showed that WEOM content ranged from 23.5 to 517.6 mg kg−1 in the soil samples. Four fluorescent components including two tryptophan-like components (C1 and C4) and two humic-like components (C2 and C3) were identified by excitation–emission matrices combined with parallel factor analysis (EEM-PARAFAC). Proportions of humic-like components (C2 + C3) were 54–66%, which is 1.2–2.0 times of the tryptophan-like component proportion (C1 + C4) for all samples. The proportions of C2 and C3 were highest in the tropical monsoon climate (TroM) zone compared to that in the other climatic zones. Structural equation model and decomposition of variation showed that soil nutrient content was the main contributing factor of soil WEOM. Content Total nitrogen content and mean annual temperature (MAT) were the main factors influencing soil HIX but they had the opposite effects. Our results suggested that increasing soil nutrient content contributed the increase in soil WEOM content, but increasing MAT reduced the humification degree of WEOM. [ABSTRACT FROM AUTHOR]

Fish represent a large part of the taxonomic diversity of vertebrates and are of high commercial value. However, the factors influencing the gut microbiota composition of freshwater fish over large spatial scales remain unclear. Therefore, this study explored gut microbiome diversity in 24 fish species from the Yellow River, which spans over 1500 km across China. The results showed that geographical distance, host phylogeny and diet significantly influenced gut microbial community diversity, whereas sex, body length and body weight had minimal influence. Geographical distance was the primary factor shaping gut microbiota, and dissimilarity in microbial community structure increased with an increase in geographical distance, which was mainly driven by dispersal limitation. The microbial communities were more homogeneous at higher host taxonomic resolutions due to the dominant role of homogeneous selection in community convergence. Phylosymbiosis was observed across all host species, with a stronger pattern in Cypriniformes, which harbour host‐specific microbial taxa. Host diet explained little variation in gut microbiome diversity, although it was significant for all diversity metrics tested. These findings collectively suggest that the geographical and host‐based patterns of fish gut microbiota tend to be shaped by different ecological forces across the Yellow River. The present work provides a robust assessment of multiple factors driving fish gut microbial community assembly and offers insight into the mechanisms underlying shifts in fish gut microbiota in rivers across large spatial scales. [ABSTRACT FROM AUTHOR]

Microbiota play essential roles in nitrogen (N) cycling in freshwater river ecosystems. However, our understanding of microbial functional groups associated with N cycling (especially denitrification) in freshwater rivers under anthropogenic disturbance is still poor. Here, we studied the impacts of different land‐use types on denitrification‐related microbiota in the Weihe River, Hanjiang River, and their tributaries, in the Qinling Mountains, China. The major land‐use types in the three river areas were divided into natural (forest, shrub, grassland, and open water) and anthropogenic (agricultural and urbanized land) types. A landscape survey of microbiota in the river water and sediment was carried out with extensive sample sources based on deep 16S rRNA gene sequencing, which yielded operational taxonomic units for predicting functional groups. With increases in proportions of agricultural and urbanized land areas, electrical conductivity, total N, ammonium‐N, and nitrate‐N all increased in water samples. Conversely, microbial diversity exhibited a decreasing trend in water samples, whereas the relative abundance of denitrification‐related functional groups increased, with increases in the proportions of agricultural and urbanized land areas. The relative abundances of denitrification‐ and human‐related microbial functional groups in sediment samples were distinctively higher in Weihe River (mainly under agriculture and urbanization), when compared with those of Hanjiang River and Qinling tributaries (dominated by forests). The results indicate that anthropogenic land‐use types, such as agricultural and urbanized land, result in simple microbial community structure and stimulate microbe‐mediated denitrification in freshwater rivers. [ABSTRACT FROM AUTHOR]

The aim of this study was to reveal the variation in dissolved organic matter (DOM) components, bacterial community composition, and their co-relationships during groundwater migration. A well-studied shallow eutrophic lake, Lake Taihu, was selected to explore the DOM components and bacterial communities during groundwater replenishment from the lake using three-dimensional fluorescence-parallel factor analysis and high-throughput sequencing, respectively. Six fluorescent components of DOM were identified, including four humic-like components (C1: λ E x / E m = 330 / 400 n m , C2: λ E x / E m = 260 , 350 / 450 n m , C3: λ E x / E m = 270 , 380 / 480 n m , and C6: λ E x / E m = 220 / 410 n m ) and two protein-like components (C4: λ E x / E m = 230 , 280 / 320 n m , C5: λ E x / E m = 230 , 290 / 340 n m ). With increasing distance to Lake Taihu, the fluorescence intensity of C1, C3, C4, and C5 decreased within 15 km away from lake shore and then tended to be stable. Thirty-three phyla of bacteria were identified in the aquifer, including Proteobacteria (61.9% of total bacteria), Bacteroidetes (15.0%), Planctomycetes (4.8%), Verrucomicrobia (3.4%), and Actinobacteria (3.3%). The relative abundance of Proteobacteria was significantly positively correlated with the fluorescence intensity of C1–C3, while the relative abundance of Actinobacteria showed the opposite relationship with the fluorescence intensity of C1–C3. The relative abundances of Novosphingobium and Limnohabitans were positively correlated with the fluorescence intensity of C4–C6. Our work suggests that the influence of groundwater replenishment from a eutrophic lake on DOM in the surrounding aquifer may extend to within 15 km from the lake shore. A large amount of DOM inputs (especially humic acid-like components) can induce variation in groundwater bacterial community composition and thus affects the groundwater biogeochemistry. [ABSTRACT FROM AUTHOR]

The upper reaches of the Han River are the source region of water for the Middle Route of China's South-to-North Water Diversion Project, mainly for household, industrial, and irrigation purposes. Planktonic bacteria are more sensitive than macroorganisms to water physical and chemical properties and play a critical role in biogeochemical processes in river ecosystems. In November 2017 and April 2018, a systematic and methodical survey was carried out to evaluate the water quality and bacterial communities, on the mainstem of the Han River and its five main tributaries. In this study, high-throughput sequencing technology has been employed to investigate the bacterioplankton community composition. The results indicated the following: (1) diversity increased downstream, especially in the upper reaches of the Han River. (2) The relative abundance of Actinobacteria increased with the increase of river length, while that of Bacteroidetes decreased slightly. (3) Five tributaries were found to be importance sources of taxa to the Han River; however, in both months, a large proportion of operational taxonomic units (37.84% and 36.34%, respectively) had unknown sources. (4) Finally, redundancy analysis (RDA) and Bioenv analysis showed that environmental parameters (pH, TN, Cond, NH4+–N, DO, NO2−–N, Chl-a, and T) had a great influence (p ≤ 0.05) on the bacterioplankton community. These research results are beneficial for the managing the ecological system, protecting the tributary biodiversity, and conserving the mainstem and tributaries of the Han River basin. [ABSTRACT FROM AUTHOR]

Little information about biodiversity patterns in high‐elevation aquatic systems has been gathered, even though these patterns are important for understanding the impacts of human activities. The source region of the Yangtze River, a typical alpine zone with vulnerable and sensitive ecosystems, was selected. Phytoplankton, which play a critical functional role as freshwater primary producers, serve as an important ecological indicator of aquatic systems. Here, systematic surveys on the water environment and phytoplankton were carried out to examine how the phytoplankton community varies with elevation based on hypothesized structural equation models (SEMs) in 10 typical rivers of the Yangtze River source region in March and October 2018. In total, 58 species of phytoplankton belonging to 28 genera were identified. The relationship between species abundance and elevation for phytoplankton showed unimodal elevational patterns. The results of the SEMs showed that all studied aspects affecting the phytoplankton community were directly or indirectly associated with elevation. The synergistic effects of human activities and basic environmental factors (terrestrial productivity and slope gradient) were the drivers affecting the phytoplankton community in the Yangtze River source region. Climate, topography, human activities and other factors are significantly different with changes in elevation, resulting in significant differences in the structure of aquatic communities at different elevations. Human activities were the major drivers affecting the phytoplankton community along the elevational gradient. As the elevation decreased, the disturbances to aquatic ecosystems caused by human activities intensified in the study area. [ABSTRACT FROM AUTHOR]

Non-point source pollution in rivers is an important factor affecting water quality. Quantifying the load of non-point source pollutants in the water and implementing improvement measures are critical for guaranteeing drinking water quality. In this study, the Dan River watershed, which is an important water source for Beijing, was investigated. Through a combination of water sampling and numerical simulations, the temporal and spatial distributions of nitrate nitrogen (NO3−-N) and ammoniacal nitrogen (NH4+-N) loads in the watershed were determined, and the effects of vegetation restoration and agricultural management on reducing nitrogen pollution in the river were predicted. The NO3−-N and NH4+-N loads in the watershed were higher during the wet season (July–September), accounting for more than 50% of the annual nitrogen output. The Soil and Water Assessment Tool (SWAT) was used to simulate the nitrogen load in the watershed. Pollution from nitrogen loading was serious in the lower reaches of the river; however, vegetation restoration can reduce the nitrogen output. Through scenario simulations, we found that an increase in forestland in the watershed would reduce the NO3−-N and NH4+-N loads. The nitrate and NH4+-N loads in the watershed also decreased with reduced fertilizer use and reduced irrigation application in the watershed. Thus, reasonable land planning and agricultural management measures can effectively reduce nitrogen loss, which is an effective way to control non-point source pollution in watersheds and ensure river water quality. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) plays an important role in aquatic ecosystems. Most previous works have focused on the source, migration, and transformation of DOM in the same water body at several sampling sites, but few studies have focused on the differences in DOM among numerous independent water bodies. This study aimed to investigate the fluorescence properties of DOM and its relationships with water quality indexes, eutrophication levels, and land use in corresponding water catchments in several independent water bodies. Five fluorescent components were identified by the EEM-PARAFAC method in the current study. The UVC humic-like component C1 (λEx/Em = 255/454 nm) and UVA humic-like component C2 (λEx/Em = 260/474 nm) were derived from terrestrial plant decomposition or soil organic matter. The UVA humic-like component C3 (λEx/Em = 300/382 nm) was produced by microbial decomposition. The tryptophan-like component C4 (λEx/Em = 280/330 nm) and the tyrosine-like component C5 (λEx/Em = 225(280)/298 nm) were caused by the discharge of sewage. Farmland contributed more to DOC concentration, humic-like components (C1–C3), and humification index (HIX) than did forest and grassland. The maximum fluorescence intensities of C1, C2, C3, and lna(254) were positively related to the trophic state index (TSI), suggesting that humic-like components and lna(254) could be used as indicators to reflect the eutrophication levels of several independent water bodies. [ABSTRACT FROM AUTHOR]

Exploring phytoplankton biodiversity and biogeographic patterns, and the factors that control them, can help to understand the structure and function of aquatic ecosystems. We selected mountain ponds with minimal anthropogenic disturbance to reveal the biogeographic patterns of phytoplankton and to assess the influence of spatial and environmental factors on phytoplankton biodiversity. On a large regional scale, the phytoplankton communities in the mountain ponds showed geographic patterns—the community composition differed between eastern and western areas. A total of seven phyla and 73 genera were identified. Alpha diversity indices did not significantly correlate with nutrient concentrations. Environmental factors and principal coordinates of neighbour matrices together explained 28.5% of the total variation in phytoplankton community composition in the 41 ponds, with each uniquely explaining 3.0% and 14.4% of the total variation, respectively. Therefore, compared with environmental factors, spatial factors predominantly contributed to the distribution of phytoplankton across the study area. With increasing trophic status, the relative influence of spatial factors decreased, while that of environmental factors increased. [ABSTRACT FROM AUTHOR]

Invasions of non-native fishes are recognized as a serious threat to freshwater biodiversity across the globe. Being the China's second-largest river, the Yellow River has experienced severe invasion pressure of non-native fishes during recent decades. However, much less is known about species composition and distribution of non-native fishes in this river basin. Here, we investigated and summarized the literatures about non-native freshwater fish in the Yellow River Basin (YRB), to examine their taxonomic diversity, geographical origin, longitudinal distribution and potential risk. We found that 40 non-native fish species, belonging to 9 orders, 18 families and 35 genera, have invaded the YRB. Of which 19 exotic species came from other regions, while 21 translocated species were introduced into the upstream from midstream and downstream of the YRB. The aquaculture was the main vectors responsible for non-native fish introductions. An average of 8.24 non-native fish species was introduced and established per sub-region, accounting for 25.5 % of total fish species. The percentage of non-native species showed a significant unimodal model against average elevation, with the highest values (ca. 70 %) in upstream mainstream reaches and tributaries. Non-native species from historically absent or species-poor orders (Salmoniformes, Osmeriformes and Perciformes) were the most successful invaders. Furthermore, the species composition of non-native fishes changed markedly along the longitudinal gradient (i.e., from source region to downstream). The negative impacts of non-native fish introductions to native fish species, e.g., competition for resource, predation and hybridization were emerged in many introduce regions and could get worse in the future due to global warming and human activities. This study can help improve the management of non-native fish introductions and biodiversity conservation of native and endemic fish species in the YRB. [ABSTRACT FROM AUTHOR]

The source regions of the Yangtze and Yellow Rivers on the Qinghai-Tibet Plateau are extremely important water resources and ecological functional areas in China, and the ecological environment is fragile and sensitive to climate change. Chromophoric dissolved organic matter (CDOM) is an important component that plays a crucial role in the biogeochemical cycle in aquatic ecosystems. However, knowledge of the distribution characteristics of CDOM in this area is limited. In this study, the optical properties, possible sources of CDOM, and their relationships with environmental variables were investigated in the two regions. The results indicated that the CDOM absorption spectra of these two source regions had a high degree of consistency, and the absorption coefficient aCDOM(355) was small, with a mean of 2.07 ± 1.10 m−1. Two fluorescence components (C1 and C2) were identified and grouped into the humic-like component with parallel factor analysis (PARAFAC) of fluorescence excitation-emission matrices (EEMs), which exhibited highly similar (excitations/emission)max positions between each pair of components in the two regions. Comprehensive CDOM spectral absorption and fluorescence parameters suggested that CDOM was mainly derived from externally input humus, and the source region of the Yellow River showed stronger allochthonous sources. The dissolved organic carbon (DOC) gradients in the water affected the fluorescence intensity and indicated that the humic-like component was an important component of DOC. Water temperature (WT) and turbidity (Turb) positively affected the concentration of CDOM and the ability to absorb light in the aquatic ecosystems. Due to global warming, the rising temperature may lead to an increase in meltwater inflow in the source area and will also bring more external inputs through the runoff. [ABSTRACT FROM AUTHOR]

This study quantified the temporal properties of precipitation and actual evapotranspiration (ETa) in the Zoige basin of the Yellow River source region, China during the 1967–2011 period, as well as their influence to the area reduction of peatland. We extracted areas of different land-use and land-cover (LULC) types and obtained daily precipitation data. Then, we calculated annual precipitation (AP) and specific cumulative precipitation (SCP), which is the sum of precipitation to the date when an image was taken, and showed that the peatland areas were strongly affected by SCP. Using a modified Penman–Monteith equation, we calculated ETa for each LULC type and the area-weighted ones to show that the area-weighted total ETa was mainly contributed from grassland and peatland, which was between 450 and 550 mm. Temporal trends of the ratio of SCP to evapotranspiration showed that precipitation was generally greater than evapotranspiration rate not only during the summer but also over the 1967–2011 period. This trend failed to completely explain the continuous decrease of peatland area in the Zoige basin in decades. The draining effect of artificial ditches and natural gullies might play an additional role in causing peatland degradation but requires further process-based studies. [ABSTRACT FROM AUTHOR]

This paper studies the influence of the impounding process during flood recession in the TGR on the distribution and rerelease of sediment phosphorus forms in the Xiangxi Bay in 2016. Influenced by the main stream of the Three Gorges Reservoir (TGR) flowing backward during impoundment, the water environmental conditions, sediment grain size and sediment-forming environment of the tributary bays change correspondingly. In this study, it is found that the water temperature (WT), turbidity and oxidation–reduction potential (ORP) of the overlying water in the Xiangxi Bay decrease, while the pH increases after impoundment in the TGR. The backward flow of the main stream containing a large amount of sediments increases the sediment content of the tributary bay, and the difference in sediment particle size between the main stream and tributaries narrows after resedimentation. The phosphorus adsorbed on the sediments increases the total phosphorus (TP) in the sediments of the Xiangxi River to 1.3 times its value before water impoundment. NaOH-P and HCl-P in the Xiangxi River sediments account for 42% and 38% of the TP, respectively, and the contents of the various phosphorus forms are ranked in the following order: NaOH-P > HCl-P > organic phosphorus (OP). After impoundment, HCl-P accounts for 67% of the TP, and the relative contents of the phosphorus forms are ranked as: HCl-P > OP > NaOH-P. Orthophosphate (PO43−-P) in the Xiangxi sediments before and after impoundment acts as a source, and the PO43−-P diffusion flux increases from approximately − 0.0029 to 0.0059 mg (m2 d)−1 before impoundment to 0.0067–0.1071 mg (m2 d)−1 after impoundment, which is mainly due to the increased difference in concentration of PO43−-P [ρ(PO43−-P)] between the sediment interstitial water and overlying water after impoundment. After nutrient recharge of the main stream of the Yangtze River, ρ(PO43−-P) of the overlying water is 3.7 times its value before impoundment, and after the release of NaOH-P in the sediments, ρ(PO43−-P) of the interstitial water is 8.3 times its value before water impoundment. Hence, the risk of nutrient release from the sediments in the Xiangxi Bay increases. [ABSTRACT FROM AUTHOR]

The Weihe River Basin plays an indispensable role in the water environment and water ecological balance in Northwest China and the lower reaches of the Yellow River. In the context of river ecosystems being affected by climate change and human activities, phytoplankton, as primary producers in food webs, serve as an important ecological indicator of environmental change. As such, systematic surveys on the water environment and phytoplankton were carried out in the Weihe River mainstem and its five tributaries from the northern foot of the Qinling Mountains from October to November 2017 and April to May 2018. In total, 154 species of phytoplankton belonging to 69 genera were identified in the heavy sediment-laden mainstem, with an average density and biomass of 177.57*104 cell L−1 and 6.53 mg L−1, respectively. Furthermore, a total of 207 species of phytoplankton belonging to 81 genera were identified in the five tributaries originating in the Qinling Mountains, with an average density and biomass of 80.98*104 cell L−1 and 1.90 mg L−1, respectively. Canonical correspondence analysis (CCA) was employed to analyze the relationship between phytoplankton communities and environmental factors. The results of data screening and Monte Carlo sequencing tests revealed that water temperature (WT), dissolved oxygen (DO), and nitrite nitrogen (NO2--N) were the primary environmental factors affecting the distribution and abundance of phytoplankton in the Weihe River mainstem. WT, flow velocity (V), pH, conductivity (Cond), and NO2--N predominantly structured the phytoplankton communities in the Weihe River tributaries. The results of this study are useful for the ecological management and conservation of the mainstem and tributaries of the Weihe River Basin. [ABSTRACT FROM AUTHOR]

For decades, the river health of the Yellow River source region (YRSR) on the Qinghai-Tibetan Plateau has been a focal issue owing to its unique geographic location and ecological functions. This study investigated the ecological status of the headwater streams, the main stem, and the tributaries of the Yellow River in the YRSR using the tolerance values of macroinvertebrates and those related to biotic indices. The macroinvertebrate assemblages of the headwater streams were characterized by lower biodiversity than the tributaries downstream, based on comparisons of taxonomical composition, functional feeding group composition, and the pollution-tolerant capacity of taxa. The headwater streams had a lower ratio (16%) of pollution-sensitive macroinvertebrate taxa than that of the tributaries downstream (30%). The biotic indices (family- and genus-level biotic indices) indicated that the ecological health of the headwater streams was comparably poorer than that of the downstream tributaries. The combined effect of vulnerable natural conditions and increasing human disturbance is likely the main cause of eco-environmental degradation in the Yellow River headwater streams. [ABSTRACT FROM AUTHOR]

Assemblage structures and distribution patterns of aquatic macroinvertebrates are influenced by riverine environmental variables. The relationship between environmental variables and macroinvertebrate assemblages, however, has rarely been examined quantitatively for rivers with high stream power at high altitude. In this study, stream power was analyzed in relation to macroinvertebrate distributions in the Yarlung Tsangpo River Basin on the Tibetan Plateau. Field investigations were carried out at 22 sites in April, 2014 and 2015. Stream power, substrate size and evenness, discharge, bedload transport, and organic detritus availability varied greatly among these sites. In total, 125 taxa of macroinvertebrates belonging to 48 families and 104 genera were identified. The macroinvertebrate density was negatively and significantly correlated with the stream power ( D = 3.30, P < 0.001). Both the assemblage indices (taxa richness, density, biomass, and the Improved Shannon-Wiener Index) and the environmental variables (elevation, substrate size, and discharge) differed among the sites with different levels of stream power. An adaptability analysis showed contrasting adaptive strengths of typical taxa. Orthocladius, Baetis, and Simulium adapted to wide ranges of stream power and their most optimal stream powers were relatively high, while Bethbilbeckia and Natarsia were only well-adapted to fairly narrow ranges in stream power. Some macroinvertebrates have evolved specific strategies to adapt to high stream power: Baetidae and Heptageniidae have developed specialized body shapes, and Epoicocladius has altered its host preference. The stream power has been shown to be significantly correlated with and could be used to predict macroinvertebrate density in the Yarlung Tsangpo River Basin. [ABSTRACT FROM AUTHOR]

The Dongting Lake, a river-connected lake, plays a vital role in people's living, agricultural production, and ecological security of the Yangtze River basin. A systematic investigation of macroinvertebrates was conducted in the Dongting Lake during May 2004 - January 2005. Altogether 65 taxa belonging to 27 families and 53 genera were identified. The annual average density and biomass of total macroinvertebrates were 265 ind/m2 and 2.40 g dry mass/m2, respectively. It is demonstrated that seasonal variation existed in environmental factors structuring macroinvertebrate assemblages of the Dongting Lake. Hydrological parameters (i.e., flow velocity, water depth) were the driving factors for macroinvertebrate assemblages in spring and summer, whereas the concentrations of water nutrients (i.e., phytoplankton chlorophyll a, total dissolved phosphorus) played the leading role in governing macroinvertebrate assemblages in autumn and winter. After operation of the Three Gorges Dam in 2009, the Dongting Lake may be confronted with the threat of species diversity declining and assemblage structure changing. Thus, ecological restoration measures shall be put forward. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 914-920, 2017 [ABSTRACT FROM AUTHOR]

Although initially designed and developed for studying large-scale open ocean dynamics, radar altimetry has proven to have the potential for monitoring coastal and inland water-level changes. However, for rough and heterogeneously reflecting surface, the shape of a waveform contains multiple peaks and traditional retracking methods do not perform well. In this study, we proposed a novel Multi-subwaveform Multi-weight Threshold Retracker (MSMWTR) method, which was applied to Jason-2 waveforms over the Yangtze River (about 1.70 km wide) during 2008–2015. Several traditional waveform retracking algorithms, including Ice-1, offset centre of gravity (OCOG) and 50% Threshold algorithms, were also used to compute water levels. By comparing retracked water levels with nearby Hankou daily gauge records, the results show that the proposed MSMWTR method can significantly improve the accuracy of the estimated water levels compared with other retrackers, especially in the dry season. After applying the MSMWTR algorithm, the root mean square of the errors decreased significantly from 9.06 to 0.34 m. The new method can significantly broaden the application of radar altimeter over relatively wide rivers. [ABSTRACT FROM AUTHOR]

The disturbance of the water-sediment interface by wind-driven currents and waves plays a critical role in sediment resuspension and internal nutrient release in large, shallow lakes. This study analyzed the effects of the interactions between wind-induced currents an1d waves on the driving mechanism of sediment resuspension in Lake Taihu, the third largest freshwater lake in China, using acoustic and optic techniques to collect long-term, high-frequency, synchronous in situ measurements of wind, currents, waves, and suspended solid concentrations (SSCs). The results suggested that water turbidity started to increase at wind speeds of approximately 4 m/s and significantly increased when wind speeds exceeded 6 m/s. In most cases, wind-induced waves were the main energy source for changes in turbidity. Wave-generated shear stress contributed more than 95% to sediment resuspension and that only in weak wind conditions (<4 m/s) did the lake bottom shear stresses generated by currents and waves contributed equally. The relationship between SSC and bottom shear stress generated by wave was established by fitting the observed results. The processes of sediment dynamics were divided into four stages (A through D) according to three shear-stress thresholds. In stage A, SSC remained stable (about 45 mg/L) and τ was less than 0.02 N/m. In stage B, the sediment bed was starting to be activated (SSC 45∼60 mg/L) and τ was in the range of 0.02∼0.07 N/m. In stage C, a medium amount of sediment was suspended (SSC 60∼150 mg/L) and τ ranged from 0.07 to 0.3 N/m. In stage D, large amount of sediment was suspended (SSC 150∼300 mg/L) and τ was larger than 0.3 N/m. The findings of this paper reveal the driving mechanism of sediment resuspension, which may further help to evaluate internal nutrient release in large shallow Lake Taihu. [ABSTRACT FROM AUTHOR]

Sediment resuspension plays an important role to provide nutrient release for algal growth in large shallow lakes. The settling velocity ( w ) is the key parameter for understanding the suspended sediment transport. In this paper, acoustic Doppler velocimeter (ADV) and optical backscatter sensor (OBS) instruments were used to measure in situ velocities and suspended sediment concentration (SSC) simultaneously without affecting the ambient turbulence in the bottom layer of Lake Taihu. The results showed that (1) ADV echo intensity (EI) could be transferred into SSC successfully by using a simple logarithmic relationship with a strong correlation of 0.87. (2) Three methods from a balance of settling and diffusive flux gradients for calculating settling velocities were applied, including Reynolds concentration flux, estimation of eddy diffusivity using the von-Karman Prandtl equation, and Kwon's power equation. The average settling velocity during the observation period was 0.11 mm/s for Lake Taihu. (3) The fitted power function, w = 1.85 × 10 C , could be used to estimate w according to SSC. (4) Settling velocity changes with SSC, vertical velocities, and wind speed, which describes suspended sediment instantaneous and continuous motions. This paper provides an effective approach for estimating the settling velocity, provides a reference value of settling velocity for hydrodynamic model, and supports a better understanding of sediment transport process and nutrient release in large shallow lakes. [ABSTRACT FROM AUTHOR]

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Total metal concentrations were determined in top and historically subhorizon contaminated sediments collected from four sampling areas (Upstream (UP), Yongping Mining Area Stream (YP), Guixi Mining Area Stream (GX), and Downstream (DM)). The sediments were analyzed for Cu, Zn, Pb, Cd, Cr, As, and Ni using a sequential extraction scheme by Tessier. The results showed that the maximum values of Cu, Zn, and Pb were in top and subhorizon sediments collected from the YP areas, while the DM areas had the highest concentrations of Cd, Cr, As, and Ni. The majority of metal values were higher than the corresponding background values and were increasingly prevalent with the following order: Ni < Cr < Pb < Zn < Cd < As < Cu. Geoaccumulation Index indicated that the contamination degree ranged from uncontaminated to strongly contaminated. The comparison of total metal concentrations in top and subhorizon sediments at depth showed a large difference in the risk to biota. When metal partitioning characteristics were also considered, over 60% of metals were potentially bioavailable and likely toxic. By means of Hierarchical Cluster Analysis, a total number of four groups were distinguished from 16 sampling sites. Sediments from different sampling sites showed an apparent trend for grouping sites, which might be attributed to the various originations of heavy metals and the disturbance from human activities. Factor analysis results revealed two sources of pollutants, which can be explained by two factors: (i) mixed origin or retention phenomena of industrial emissions and (ii) terrigenous. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 713-723, 2015 [ABSTRACT FROM AUTHOR]

The water quality of East Lake, the largest urban lake in China, has continuously deteriorated as a result of urban development. To improve the lake's water quality, a diversion construction project is underway to divert water from the Yangtze River to the lake to accelerate the flow cycle and decrease nutrient concentrations. This study assessed the effects of proposed diversion schemes on water quality using the composite water quality identification index (CWQII) method and a 2-dimensional (2D) water quality model. The study results indicated that the water quality of the lake is strongly influenced by diversion schemes, including diverting locations, discharge, and time. The optimum diversion inlet was inlet 2 (located in Shuiguo Bay), and the most efficient discharge was 30 m3/s. Diverting from different inlet locations caused more obvious reduction rates of CWQII in summer (Jul) than in winter (Jan). After diversion, CWQII values throughout the entire lake were reduced, and the spatial distribution of CWQII became more homogeneous. The highest reduction of CWQII occurred near the inlet location. The CWQII method and 2D water quality model provided a relevant example for assessing the general water quality and designing optimal schemes for diversion projects to improve water quality in large shallow lakes. [ABSTRACT FROM AUTHOR]

Aquatic ecosystems of highland rivers are different from those of low altitude rivers because of the specific topography and environmental parameters associated with high altitudes. Yalutsangpo, the upper course of the Brahmaputra River, is the highest major river in the world, flowing from west to east across Tibet, China and pouring into India. Macroinvertebrates were sampled from Yalutsangpo and its tributaries, the Lhasa, Niyang, and Parlong Tsangpo Rivers, from October 2009 to June 2010, to study characters of the highland aquatic ecosystem. Altogether, 110 macroinvertebrate taxa belonging to 57 families and 102 genera were identified from the basin. The biodiversity and composition of macroinvertebrate assemblages were strongly affected by altitude gradients. Local diversity represented by taxa richness and the improved Shannon-Wiener index were high at altitudes of 3,300-3,700 m, among which suitability of habitat was higher due to the better integrated environmental conditions of water temperature, dissolved oxygen, and aquatic vegetation, etc. Macroinvertebrates were grouped into shredders, scrapers, predators, collector-filterers, and collector-gatherers according to their feeding behaviors. It was found that the distributions of the functional feeding groups varied with habitat altitudes. Shredders were present at altitudes of 2,900-4,400 m, while scrapers mainly inhabited altitudes of 3,500-4,500 m, and collector-filterers preferred 3,500-4,000 m. Even though the local taxa richness was not high at each site, the taxonomic composition and density of the assemblages varied greatly among the different sites, resulting in much higher regional diversity compared to the lowland river with similar flow and substrate conditions. The regional cumulative taxa richness of Yalutsangpo decreased and more families were lost as the altitude increased. However, some families that were newly present as the altitude increased were essential for sustaining the high regional biodiversity. The ordination diagram obtained from Detrended Correspondence Analysis indicated that altitude, river pattern, riverbed structures, bank structures, and flow conditions were the main factors that influenced the macroinvertebrate assemblages in the Yalutsangpo basin. [ABSTRACT FROM AUTHOR]

Composite Water Quality Identification Index (CWQII) and multivariate statistical techniques were used to investigate the temporal and spatial variations of water quality in Honghu Lake. The aims are to explore the characteristics of water quality trends in annual, monthly, and site spatial distribution and to identify the main pollution factors. The results showed that the values of CWQII increased from 2.0 to 4.0 from the years 2001 to 2005, then decreased from 2006 and kept a balance between 2.0 and 3.0 from 2006 to 2011, indicating that the water quality of Honghu Lake deteriorated from 2001 to 2005 and has gradually improved since 2006, which were likely achieved after water protection measurements taken since 2004. The monthly change rules of water quality were influenced by a superposition of natural processes and human activities. In samples numbered 1-9 from upstream to downstream, the maximum values of CWQII often occurred in sample site 9 while the minimum ones often occurred in sample site 2, indicating that the water quality near the upstream tributary was the poorest and that in the core zone was the best. Incoming water from the trunk canal of the Sihu area upstream was the largest pollution source. The sensitive pollution nutrients were mainly caused by the total nitrogen, followed by the total phosphorus. [ABSTRACT FROM AUTHOR]

Many large rivers in China have an inflow of contaminated water. Water pollution caused by urban sewage and agriculture, and occasionally pollution events from industries have become a significant stress on aquatic ecology. Pollution affects the biodiversity of the aquatic community and the species composition changes from natural species to tolerant species. The species composition of aquatic animals may reflect water pollution level. Extremely non-uniform distributions of functional feeding groups occurred as a result of high nutrient levels. A combination of chemical and biological methods constitutes the best approach for biological monitoring studies that measure water quality. Macroinvertebrates were used as bio-assessment indicator to determine the environmental quality of given water body. In this study, samples of water and macroinvertebrates were taken from several dozen sites in 14 rivers in China with different pollution levels, including the Yangtze, East, Weihe, Songhua, Yongding, and Panlong rivers. Macroinvertebrates were identified to genus or family level. Water samples were classified into different water quality grades according to the concentration of different substances. Five biological indices: taxa richness ( S), density ( D), total BMWQ score (t-BMWQ), average BMWQ score (a-BMWQ), and the family biotic index (FBI) were used for biological assessment of water quality. Analyzing macroinvertebrates' occurrence in different water quality levels, taxa-specific indicators, which are defined as the taxa of macroinvertebrates that live in a certain water quality level but do not exist in other water quality levels were proposed for water quality bio-assessment. Leptophlebiidae, Siphlonuridae, Arctopsychidae, Perlidae, and Antocha sp. are the taxa-specific indicators for very good or good water quality; Chironomidae, Lymnaeidae, Tubifex sp., Limnodrilus sp., Limnoperna lacustris, Corbicula sp., Macrobrachium sp., Planorbidae, Glossiphoniidae, and Branchiura sp. are the taxa-specific indicators for very poor water quality; and Psychomyiidae and Hydroptilidae are the taxa-specific indicators for moderate water quality. [ABSTRACT FROM AUTHOR]

The spatial distribution of valley setting (laterally-unconfined, partly-confined, or confined) and fluvial morphology in the source region of the Yangtze and Yellow Rivers is contrasted and analyzed. The source region of the Yangtze River is divided into 3 broad sections (I, II and III) based on valley setting and channel gradient, with the upstream and downstream sections being characterized by confined (some reaches partly-confined) valleys, while the middle section is characterized with wide and shallow, laterally-unconfined valleys. Gorges are prominent in sections I and III, while braided channel patterns dominate section II. By contrast, the source region of the Yellow River is divided into 5 broad sections (sections I-V) based on valley characteristics and channel gradient. Sections I, II and IV are alluvial reaches with mainly laterally-unconfined (some short reaches partly-confined) valleys. Sections III and V are mainly confined or partly-confined. Greater morphological diversity is evident in the source region of the Yellow River relative to the upper Yangtze River. This includes braided, anabranching, anastomosing, meandering and straight alluvial patterns, with gorges in confined reaches. The macro-relief (elevation, gradient, aspect, valley alignment and confinement) of the region, linked directly to tectonic movement of the Qinghai-Tibet Plateau, tied to climatic, hydrologic and biotic considerations, are primary controls upon the patterns of river diversity in the region. [ABSTRACT FROM AUTHOR]

This study presents findings of the first systematic analysis of aquatic biotic assemblages in the source region of the Yellow and Yangtze Rivers. It provides an initial basis with which to select representative organisms as indicators to assess the aquatic ecological status of rivers in this region. Macroinvertebrates are considered to be good indicators of long-term environmental changes due to their restricted range and persistence over time. Field investigations of macroinvertebrates were conducted in August 2009 in the source region of the Yellow River, and in July 2010 in the source region of the Yangtze River. Altogether 68 taxa of macroinvertebrates belonging to 29 families and 59 genera were identified. Among them were 8 annelids, 5 mollusks, 54 arthropods and 1 other animal. In the source region of the Yellow River, taxa number, density and biomass of macroinvertebrates were 50, 329 individuals m and 0.3966 g dry weight m, respectively. Equivalent figures for the source region of the Yangtze River were 29, 59 individuals m and 0.0307 g dry weight m. The lower benthic animal resources in the source region of the Yangtze River are ascribed to higher altitude, higher sediment concentration and wetland degradation. Preliminary findings of this exploratory study indicate that hydroelectric power stations had a weak impact on benthic dwellers but wetland degradation caused by a series of human activities had a catastrophic impact on survival of macroinvertebrates. Ecological protection measures such as conservative grazing and vegetation management are required to minimize grassland degradation and desertification, and reduce soil erosion rate and river sediment discharge. [ABSTRACT FROM AUTHOR]

The 270 km long section of the Upper Yellow River at the First Great Bend is comprised of single channel and multiple channel systems that alternate among anastomosing, anabranching, meandering and braided reaches. The sequence of downstream pattern changes is characterized as: anastomosing-anabranching, anabranching-meandering, meandering-braided and braided-meandering. Remote sensing images, DEM data and field investigations are used to assess and interpret controls on these reach transitions. Channel slope and bed sediment size are key determinants of transitions in channel planform. Anastomosing reaches have a relatively high bed slope (0.86‰) and coarser sediment bed material ( d = 3.5 mm). In contrast, meandering reaches have a low slope (0.30‰) and fine sediment bed material ( d = 0.036 mm). The transition from a meandering to braided pattern is characterized by an increase in channel width-depth ratio, indicating the important role of bank strength (i.e. cohesive versus non-cohesive versus channel boundaries). Interestingly, the braided-meandering and meandering-braided transitions are coincident with variable flow inputs from tributary rivers (Baihe and Heihe rivers respectively). Theoretical analysis of the meandering-braided transition highlights the key control of channel width-depth ratio as a determinant of channel planform. [ABSTRACT FROM AUTHOR]

Eutrophication can shift lakes from a clear, macrophyte-dominated state to a turbid, algae-dominated state, and different habitat condition supports different fauna. Macrozoobenthos are good indicators of water environment, and studies on macrozoobenthic assemblage characteristics can help us to know which state a lake is in, thus provide the basis for its eutrophication control. In this study, a systematic investigation on macrozoobenthos was conducted in 17 Yangtze-isolated lakes to explore the macroecological laws of macrozoobenthic assemblages. Detrended correspondence analysis (DCA) revealed that variance of benthic assemblage structure occurred in two types of lakes. In macrophytic lakes, altogether 51 taxa of macrozoobenthos were identified. The average density and biomass of total macrozoobenthos were 2231 individuals·m and 1.69 g dry weight·m, respectively. Macrozoobenthic assemblage was characterized by dominance of scrapers (i.e. gastropods). In algal lakes, altogether 20 taxa of macrozoobenthos were identified. The average density and biomass of total macrozoobenthos were 2814 individuals·m and 1.38 g dry weight·m, respectively. Macrozoobenthic assemblage was characterized by dominance of collector-gatherers (i.e. oligochaetes). Wet biomass of submersed macrophytes ( B) and phytoplankton chlorophyll a concentration ( Chl a) were demonstrated as the key factor structuring macrozoobenthic assemblages in macrophytic and algal lakes, respectively. [ABSTRACT FROM AUTHOR]

A low-cost composite of activated charcoal supported titanate nanotubes (TNTs@AC) was developed via the facile hydrothermal method to remove the 17β-estradiol (E2, a model of pharmaceutical and personal care products) in water matrix by initial adsorption and subsequent photo-degradation. Characterizations indicated that the modification occurred, i.e., the titanate nanotubes would be grafted onto the activated charcoal (AC) surface, and the micro-carbon could modify the tubular structure of TNTs. E2 was rapidly adsorbed onto TNTs@AC, and the uptake reached 1.87 mg/g from the dual-mode model fitting. Subsequently, the adsorbed E2 could be degraded 99.8% within 2 h under ultraviolet (UV) light irradiation. TNTs@AC was attributed with a unique hybrid structure, providing the hydrophobic effect, π−π interaction, and capillary condensation for E2 adsorption, and facilitating the electron transfer and then enhancing photocatalytic ability for E2-degradation. In addition, the removal mechanism of E2 was elucidated through the density functional theory calculation. Our study is expected to provide a promising material for environmental application. [ABSTRACT FROM AUTHOR]

In the present study, we choose the Weishan Lake, one of important water transfer and storage lakes on the eastern route of the South-to-North Water Diversion Project (SNWD) in China, to clarify how the community structure and assemblage-environment relationships of macroinvertebrates varied across three typical habitats (the River Mouth, Canal and Lake regions) over the four seasons in 2012. A total of 72 taxa belonging to 3 phyla, 9 classes and 24 families were recorded, with tolerant oligochaetes and chironomids as the dominant taxa. The environmental conditions and macroinvertebrate assemblages were clearly separated at spatial and temporal scales. Assemblage structure showed both significant but larger spatial than seasonal variations, with a clear separation of sites from three regions in an ordination plot. Compared to the temporal scale, more indicator species were retained to be responsible for the regional differences according to the two-way cluster analysis. Different environmental variables were significant for distinguishing macroinvertebrate assemblages among four seasons, and among them, pH was the only variable which was retained in all models. Our study provided useful background information of environmental characteristics and macroinvertebrate communities in a typical water transfer and storage lake before the water transfer of the SNWD. After the operation of SNWD, we envisage inter-basin water transfer (IBWT), which is usually accompanied by water level rise, nutrient pattern change and biota succession, will seriously affect recipient basins. Therefore, we propose several management strategies for SNWD: (1) target and detailed data should be collected on a timely basis; (2) government should prevent water pollution and adopt effective measures to protect the water environment; (3) the environmental assessments and other aspects of IBWT planning should be coordinated; (4) an overall consideration of different basins should be given to achieve a greater range of water resources planning, scheduling, and allocation; and (5) the migration and invasion of species should be of concern during the operation of the project. [ABSTRACT FROM AUTHOR]

Highland running-water biodiversity has gained growing interest around the world, because of the more pristine conditions and higher sensitivity to environmental changes of highland rivers compared to the lowland rivers. This study presents the findings of systematic investigations and analyses on running-water biodiversity of macroinvertebrate assemblages in the most important headwater streams in the Yalutsangpo and Sanjiangyuan River basins in the Qinghai-Tibet Plateau and the lowland headwaters of the Songhua River, Juma River, and East River during the non-flood seasons of 2012 to 2016. The results indicated that the headwaters on the plateau had a higher regional biodiversity compared to the lowland rivers with the similar flow and substrate conditions. Even though the local diversity of the highland rivers was not significantly different at each single site, the taxonomic composition was significantly different with several rarely seen species scattering among the different sites, resulting in a high regional biodiversity. The biodiversity and composition of macroinvertebrates were strongly affected by the altitude gradient and the environmental variables associated with altitude. To be specific, for the Yalutsangpo River, canonical correspondence analyses of the macroinvertebrate assemblages and their environmental variables indicated that altitude, stream condition (represented by river pattern, riverbed structures, substrate composition), and water temperature influence macroinvertebrate taxa composition. Because of the restrictive plateau conditions including low water temperature, poor aquatic and riparian vegetation, and low runoff, the macroinvertebrate assemblages showed low biodiversity and were vulnerable to potential human disturbance/climate change. Therefore, it is essential to conserve suitable conditions of the determinative environmental variables to protect the unique and high regional biodiversity of the headwaters on the Qinghai-Tibet Plateau. [ABSTRACT FROM AUTHOR]