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Flooding is an important process in natural fluvial floodplains. How the flood shapes aquatic community diversity in highland floodplains is still poorly understood. The aim of this study was to unravel the multi-faceted responses of benthic macroinvertebrate diversity to flooding and habitat environments in the Baihe River Basin from a taxonomic, phylogenetic, and functional perspective. We examined the alpha and beta diversity patterns of benthic macroinvertebrate communities in the mainstream, tributaries, and oxbow lakes during the normal water and flood periods. The results showed that the traditional alpha taxonomic diversity (TD) varied across habitats, despite minor changes after flood pulse. Alpha phylogenetic diversity (PD) decreased and alpha functional diversity (FD) markedly increased after flooding, with functional traits transiting toward risk avoidance. While all the three facets of beta diversity significantly responded to habitat differences, beta TD and PD shifted in response to flooding. Species turnover prominently increased in beta TD and PD after flood pulse, which contrasted with a weaker response of this process in FD. The explanatory power of significant environmental factors on both alpha and beta diversity was reduced by flooding. Compared with traditional TD, cooperating multi-faceted diversity could better depict the responses of benthic macroinvertebrate communities to flooding. The assessment and conservation of aquatic biodiversity in highland floodplains should take into account the three facets of alpha and beta diversity.
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Biodiversidade , Inundações , Invertebrados , Animais , Invertebrados/fisiologia , China , Rios , Filogenia , EcossistemaRESUMO
In floodplains, phytoplankton communities are mainly shaped by environmental heterogeneity, hydrological connectivity, and habitat diversity. However, it remains unclear how hydrological connectivity drives phytoplankton biodiversity in floodplain lakes. This study was carried out in the Dongting Lake connected to the Yangtze River to ascertain the response mechanisms of phytoplankton communities to different hydrological connectivity gradients. We quantified the hydrological connectivity between lake and river habitats using in-lake water turnover time, and identified its relationship with phytoplankton community structure. Changes in hydrological connectivity can lead to different hydrodynamic and environmental conditions, which have a direct or indirect impact on phytoplankton community structure in water environments. The results showed that spatiotemporal changes in the hydrological connectivity and water environment led to distinct spatial variation in phytoplankton community structure across the study area. α and ß diversity showed a consistent change law with the change of turnover time, and the diversity index gradually increased with the decrease of hydrological connectivity, reaching the maximum value at the moderate hydrological connectivity, and then gradually decreasing. The peak of ß diversity occurs earlier than the peak of α diversity during the decline of hydrological connectivity. This study demonstrates that in-lake water turnover time has a non-negligible impact on phytoplankton community distribution in river-connected lakes. Phytoplankton can maintain the highest α diversity and possibly ß diversity under moderate hydrological connectivity, which is crucial for maintaining aquatic biodiversity in floodplain lakes.
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Biodiversidade , Lagos , Fitoplâncton , Rios , EcossistemaRESUMO
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.
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Microbioma Gastrointestinal , Animais , Microbioma Gastrointestinal/genética , Rios , Peixes , Evolução Biológica , Filogenia , Dieta , RNA Ribossômico 16S/genéticaRESUMO
Dissolved organic matter (DOM) is the largest carbon pool and directly affects the biogeochemistry in lakes. In the current study, fourier transform ion cyclotron mass spectrometry (FT-ICR-MS) combined with fluorescent spectroscopy was used to assess the molecular composition and driving mechanism of DOM in 22 plateau lakes in Mongolia Plateau Lakes Region (MLR), Qinghai Plateau Lakes Region (QLR) and Tibet Plateau Lakes Region (TLR) of China. The limnic dissolved organic carbon (DOC) content ranged from 3.93 to 280.8 mg L-1 and the values in MLR and TLR were significantly higher than that in QLR. The content of lignin was the highest in each lake and showed a gradually decreasing trend from MLR to TLR. Random forest model and structural equation model implied that altitude played an important role in lignin degradation while the contents of total nitrogen (TN) and chlorophyll a (Chl-a) have a great influence on the increase of DOM Shannon index. Our results also suggested that the inspissation of DOC and the promoted endogenous DOM production caused by the inspissation of nutrient resulted in a positive relationship between limnic DOC content and limnic factors such as salinity, alkalinity and nutrient concentration. From MLR to QLR and TLR, the molecular weight and the number of double bonds gradually decreased but the humification index (HIX) also decreased. In addition, from the MLR to the TLR, the proportion of lignin gradually decreased, while the proportion of lipid gradually increased. Both above results suggested that photodegradation was dominated in lakes of TLR, while microbial degradation was dominated in lakes of MLR.
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Matéria Orgânica Dissolvida , Lagos , Lagos/química , Clorofila A , Ciclotrons , Análise de Fourier , Lignina , Espectrometria de Massas , Análise Espectral , ChinaRESUMO
Dispersal is an essential natural process that influences community assembly, yet directional dispersal through wind and water may have distinctive effects. Environmental and spatial factors jointly influence community structure, but their relative importance is anticipated to vary with spatial distance, dispersal mode, and season. Accordingly, a systemic survey was conducted in subtropical Chinese mountain lotic systems to distinguish the relative contributions of environmental control and spatial structuring upon communities of macroinvertebrates with different dispersal ability. Macroinvertebrate samples were collected from the upper reaches and five tributaries of the Hanjiang River in October 2017 (autumn) and April 2018 (spring). These macroinvertebrates were identified and classified into three dispersal groups: aquatic passive (AqPa), terrestrial passive (TePa), and terrestrial active (TeAc). Variation partitioning analyses were performed on environmental factors and different sets of spatial factors (overland dispersal: Overland, directional downwind dispersal: AEM_Wind, along watercourse dispersal: Watercourse, and directional downstream dispersal: AEM_Water). Findings showed that both environmental filtering and spatial structuring influenced the structure of macroinvertebrate metacommunities. For AqPa and TePa groups, pure environmental effects were stronger than pure spatial effects based on most distance matrices; however, in AEM_Water, the effects of spatial processes surpassed those of environmental filtering. For TeAc group, the role of environmental control and spatial structuring varied depending on different spatial models. The results also highlighted seasonal shifts in metacommunity structuring processes. Spatial structures featuring direction, especially AEM_Water, were predominant in explaining the construction of macroinvertebrate communities. This work suggests that directional dispersal should be explicitly considered when examining the structure of ecological communities.
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Ecossistema , Rios , Biota , Trietilenofosforamida , ÁguaRESUMO
Phytoplankton play a crucial role in energy flow and carbon cycling in aquatic ecosystems; however, exploring the driving factors influencing phytoplankton, especially in heavily sediment-laden rivers, is challenging. We analyzed 704 samples from 44 sampling sites along the Yellow River to investigate the biogeographic, environmental, and anthropogenic impacts on the phytoplankton community composition. Using cluster analysis, we identified three different phytoplankton community compositions in Regions â , â ¡, and â ¢, which were consistent with the three primary changes in the water-surface slope across the three regions. The sampling results showed that the Bacillariophyta primarily consisted of Navicula, Cyclotella, Synedra, Fragilaria, Gyrosigma, Diatoma, and Asterionella. In addition, representation by Chlorophyta was dominated by Chlamydomonas, Pandorina, Closteriopsis, and Closterium, while Phormidium was the dominant Cyanophyta genus. The variation partitioning results indicated that spatial factors (geographic distance) were the most important determinants of phytoplankton community succession. Additionally, our results highlighted that the influence of spatial and climatic factors on the succession of the phytoplankton community structure was much greater than that of the water quality. Compared to that in the free-flowing river, the phytoplankton biomass in the impoundment was much higher, and the phytoplankton community was dominated by Dinophyta, Chlorophyta, and Cyanophyta, primarily because of anthropogenic impacts. Based on the composition and biomass of phytoplankton communities in different regions, the phytoplankton community composition in the Yellow River was found to be primarily influenced by the erosion of the watershed and the inflow of tributaries rather than by limited in situ algae growth.
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Diatomáceas , Fitoplâncton , Efeitos Antropogênicos , China , Ecossistema , Monitoramento Ambiental , Rios , Estações do AnoRESUMO
Revealing the patterns and their mechanisms of microbial community in water transfer projects, especially in inter-basin water transfer projects, is the premise of biohazard warning, water quality monitoring and sustainable management of water resources. Using a river and impounded lakes from the eastern route of South-to-North Water Transfer project as a model system, we studied the diversity and assembly patterns of bacterial communities in artificially connected ecosystems and their influencing factors. Our results showed that water quality improved during the water transfer period (WTP). Further, the latitudinal pattern of bacterioplankton was reversed, which was mainly due to the change of evenness caused by water transfer and had no significant correlation with water quality parameters. Importantly, the spatial heterogeneity of the bacterial communities decreased during the WTP, and the differences in the communities between the impounded lakes and river was more significant in the non-water transfer period (NWTP) than in the WTP, which was the result of water transfer and water quality. Overall, bacterial community was largely shaped by stochastic processes. The bacterial communities had a higher migration rate during the WTP than during the NWTP. We believe that the water transfer increased the risk of biological homogenization while improving water quality. Combined, our work systematically discusses the microbial community pattern and mechanism in the inter-basin water transfer project, providing theoretical support for inter-basin water transfer project planning management and ecological environment protection.
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Microbiota , Qualidade da Água , Bactérias , China , Lagos , Rios/microbiologia , Recursos HídricosRESUMO
We measured the concentrations of Cr, Fe, Ni, Cu, Zn, Cd, Pb and Hg, and the stable isotope ratios (δ13C and δ15N) in 87 fish samples within 12 economic fish species collected from the Dongting Lake, the second largest freshwater lake in China. With few exceptions in concentration of Cr, most of fish species showed lower concentrations of the 8 metals than legislation thresholds. Piscivorous fishes had significantly higher values of δ15N (possessing higher trophic level) and metal concentrations than planktivorous and herbivorous fishes. Moreover, demersal fishes showed higher concentrations of Cu, Zn, Cd and Pb than pelagic and benthopelagic fishes. We found positive correlations between concentrations of Fe, Pb and Hg and δ15N ratio, confirming the biomagnification of the three metals through trophic transfer. In contrast, fishes showed clear growth dilution effect for Ni, Zn, Cu, Pb and Hg, indicated by the negative correlations between their concentrations and fish weight or length. Multiple regression analysis demonstrated that growth dilution and biomagnification effects simultaneously governed the metal concentrations in fish muscle, and the two effects' importance varied among different metals. The human health risk assessment indicated that all 8 metals gave target hazard quotient (THQ) values < 1.0, i.e., the estimated daily intake (EDI) of metals did not exceed the oral reference dose (RfD), indicating a safe consumption of these fish species for consumer. Our study provides comprehensive approaches to better understand the determining processes and potential risk of heavy metals in freshwater lake fishes.
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Metais Pesados , Poluentes Químicos da Água , Animais , Tamanho Corporal , China , Ecossistema , Monitoramento Ambiental , Peixes , Hábitos , Humanos , Lagos , Metais Pesados/análise , Medição de Risco , Poluentes Químicos da Água/análiseRESUMO
Trace metal contamination in water and bioaccumulation in aquatic organisms are human health risks of increasing concern. However, the bioaccumulation of trace metals in the organs of the mussel Cristaria plicata in Dongting Lake, China and the human health risks of mussel consumption are largely unknown. We investigated the concentrations of 15 trace metals and metalloids in surface water, sediments, and C. plicata organs (foot, gill, mantle, and visceral mass) and quantified the bioaccumulation and human health risk of these trace metals in specimens collected from Dongting Lake. The concentrations of most metals in surface water exceeded previously published background values. In contrast, the concentrations of most metals in sediments showed a decreasing trend. Overall, the metal concentrations in the gill and visceral masses of C. plicata were higher than those in the foot and mantle, and higher bioaccumulation capacities were observed for essential metals than for nonessential metals. The mean concentrations of the trace elements Zn, Pb, Cd, As, Cu, and Cr in C. plicata foot samples were lower than the threshold values established by international and Chinese organizations. The estimated daily intake (EDI) values of the essential metal Mn in C. plicata foot was higher than the recommended tolerable daily intake (TDI) values for juveniles. Only Mn for juveniles and As for both juveniles and adults may pose noncarcinogenic health risks through foot consumption. The hazard index (HI) values for adults and juveniles were higher than 1, suggesting significant risks of noncarcinogenic effects to humans by exposure to multiple metals.
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Bivalves , Metais Pesados , Poluentes Químicos da Água , Adulto , Animais , Bioacumulação , China , Monitoramento Ambiental , Sedimentos Geológicos , Humanos , Lagos , Metais Pesados/análise , Medição de Risco , Poluentes Químicos da Água/análiseRESUMO
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.
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Lagos/química , Poluentes Químicos da Água/análise , Qualidade da Água/normas , China , Humanos , Nitrogênio/análise , Nitrogênio/normas , Fósforo/análise , Fósforo/normas , Análise Espaço-Temporal , Poluentes Químicos da Água/normasRESUMO
The basis for submerged plant restoration in surface water is to research the complicated dynamic mechanism of water transparency. In this paper, through the impact factor analysis of water transparency, the suspended sediment, dissolved organic matter, algae were determined as three main impactfactors for water transparency of Neijiang River in Eastern China. And the multiple regression equation of water transparency and sediment concentration, permanganate index, chlorophyll-a concentration was developed. Considering the complicated transport and transformation of suspended sediment, dissolved organic matter and algae, numerical model of them were developed respectively for simulating the dynamic process. Water transparency numerical model was finally developed by coupling the sediment, water quality, and algae model. These results showed that suspended sediment was a key factor influencing water transparency of Neijiang River, the influence of water quality indicated by chemical oxygen demand and algal concentration indicated by chlorophyll a were indeterminate when their concentrations were lower, the influence was more obvious when high concentrations are available, such three factors showed direct influence on water transparency.
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Monitoramento Ambiental , Modelos Teóricos , Rios/química , Poluentes Químicos da Água/química , China , Fertilizantes , CinéticaRESUMO
Community coalescence denotes the amalgamation of biotic and abiotic factors across multiple intact ecological communities. Despite the growing attention given to the phenomenon of coalescence, there remains limited investigation into community coalescence in single and multiple source habitats and its impact on microbial community assemblages in sinks. This study focused on a major river catchment in northern China. We investigated microbial community coalescence across different habitats (i.e., water, sediment, biofilm, and riparian soil) and seasons (i.e., summer and winter). Using 16S rRNA gene amplicon sequence variants, we examined the relationship between community coalescence and microbial diversity, assembly processes, and species coexistence. The results showed that the intensity of microbial community coalescence was higher in the same habitat pairs compared to disparate habitat pairs in both summer and winter. During the occurrence of microbial community coalescence, the assembly processes regulated the intensity of coalescence. When the microbial community exhibited strong heterogeneous selection (heterogeneous environmental conditions leading to more dissimilar community structures), the intensity of community coalescence was low. With the assembly process shifted towards stochasticity, coalescence intensity increased gradually. However, when homogeneous selection (homogeneous environmental conditions leading to more similar community structures) predominantly shaped microbial communities, coalescence intensity exceeded the threshold of 0.25-0.30. Moreover, the enhanced intensity of community coalescence could increase the complexity of microbial networks, thereby enhancing species coexistence. Furthermore, the assembly processes mediated the relationship between community coalescence and species coexistence, underscoring the pivotal role of intermediate intensity of community coalescence in maintaining efficient species coexistence. In conclusion, this study highlights the crucial role of community coalescence originating from single and multiple source habitats in shaping microbial communities in sinks, thus emphasizing its central importance in watershed ecosystems.
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Biodiversidade , Microbiota , RNA Ribossômico 16S , Rios , China , Rios/microbiologia , Ecossistema , Monitoramento Ambiental , Estações do AnoRESUMO
Plateau lakes characterized by salinization and eutrophication are essential aquatic ecosystems. A myriad of microorganisms serve as crucial biological resources in plateau lakes and drive the elemental cycles of these ecosystems. Currently, there is a paucity of knowledge regarding the impacts of salinization and eutrophication dynamics on the microbiota in plateau lakes. Here, high-throughput sequencing of the 16S ribosomal RNA genes (V4 region) was used to characterize microbial community structure and assembly in plateau lakes with different salinities and trophic levels. Water samples were collected at 191 sites across 24 lakes on the Qinghai-Tibet and Inner Mongolia Plateaus in northern China. The results showed that high salinity considerably reduced microbial alpha-diversity and niche breadth while increasing within-group similarity among various lake types. High salinity additionally decreased the complexity of microbial networks and enhanced network robustness. The assembly of microbial communities was primarily governed by deterministic processes in high-salinity and eutrophic low-salinity lakes. At decreased salinity, trophic level played a leading role in shaping microbial community structure, and the ecological processes shifted from deterministic processes driven by high salinity to eutrophication-driven deterministic processes. The biomarkers also varied from taxa adapted to high-salinity environments (e.g., Nanoarchaeaeota, Rhodothermia) to those suited for living in freshwater and low-salinity habitats (e.g., Alphaproteobacteria, Actinobacteria). In the case of eutrophication, Actinobacteria, Chloroflexi, and Cyanobacteria became the dominant taxa. Our findings indicate that decreased salinity enables trophic level to play an enhanced role in shaping microbial community structure and assembly in plateau lakes. This study enriches our knowledge about the ecological impacts of salinization and eutrophication in plateau lakes.
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Cianobactérias , Microbiota , Tibet , Lagos/química , Salinidade , ChinaRESUMO
The Qinghai-Tibetan Plateau has a booming tourism industry and an increasingly sophisticated road system. There is a paucity of studies quantifying the contributions of anthropogenic and natural factors to microplastic pollution in remote plateau areas. In this study, water and sediment samples were collected from eight lake tourist attractions and four remote lakes in northern and southern regions of the Qinghai-Tibetan Plateau. Microplastics were detected in all samples, with a mean abundance of 0.78 items/L in water and 44.98 items/kg in sediment. The abundance of microplastics in the study area was lower than previously observed in more populated areas of China. Small-sized (<1 mm and 1-2 mm), fiber, and transparent microplastics were predominant, with polyethylene and polypropylene microplastics as the primary polymer types. The compositions of microplastic communities indicated that tourism and road networks were the major sources of microplastics in the lakes. Distance-decay models revealed greater influence of environmental distances on microplastic community similarity than geographic distance. Compared to climate factors, urban spatial impact intensity and traffic flow impact played a leading role in the structuring of microplastic communities in lake water and sediment. Our findings provide novel quantitative insights into the role of various factors in shaping the distribution patterns of microplastic communities in plateau lakes.
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Plateau lakes (e.g., freshwater and saltwater lakes) are formed through intricate processes and harbor diverse microorganisms that mediate aquatic ecosystem functions. The adaptive mechanisms of lake microbiota to environmental changes and the ecological impacts of such changes on microbial community assembly are still poorly understood in plateau regions. This study investigated the structure and assembly of planktonic bacterial communities in 24 lakes across the Qinghai-Tibetan and Inner Mongolia Plateaus, with particular focus on habitat generalists, opportunists, and specialists. High-throughput sequencing of the 16S ribosomal RNA genes revealed that bacterial generalists had a lower species number (2196) but higher alpha diversity than the specialist and opportunist counterparts. Taxonomic dissimilarity and phylogenetic diversity analyses unraveled less pronounced difference in the community composition of bacterial generalists compared to the specialist and opportunist counterparts. Geographical scale (14.4 %) and water quality (12.6 %) emerged as major ecological variables structuring bacterial communities. Selection by water temperature and related variables, including mean annual temperature, elevation, longitude, and latitude, mainly shaped the assembly of bacterial generalists. Ecological drift coupled with selection by salt ions and related variables, including total phosphorus, chlorophyll a, and salinity, predominantly drove the assembly of bacterial specialists and opportunists. This study uncovers distinct bacterial responses to interacting ecological variables in diverse plateau lakes and the ecological processes structuring bacterial communities across various lake habitats under anthropogenic disturbance or climate change.
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Bactérias , Lagos , Microbiota , Temperatura , Lagos/microbiologia , Lagos/química , Bactérias/classificação , Bactérias/genética , Salinidade , China , RNA Ribossômico 16S , Microbiologia da Água , FilogeniaRESUMO
Microbial communities assemble stochastically and deterministically, but how different assembly processes shape diatom community structure across riverine habitats is unclear, especially in sediment-laden environments. In this study, we deciphered the mechanisms of riverine diatom community assembly in the water column and riverbed substrate with varying sediment concentrations. Water and sediment samples were collected from 44 sampling sites along the Yellow River mainstream during two seasons. Diatom communities were characterized based on high-throughput sequencing of the 18S ribosomal RNA genes coupled with multivariate statistical analyses. A total of 198 diatom species were taxonomically assigned, including 182 free-living and particle-attached species and 184 surface-sediment species. Planktonic communities were structurally different from benthic communities, with Cyclotella being dominant mainly in the middle and lower reaches of the river with higher sediment concentrations. Both stochastic and deterministic processes affected diatom community assembly in different habitats. Species dispersal was more important in the water than in the substrate, and this process was strengthened by increased sediment concentration across habitats. Diatom communities exhibited lower network complexity and enhanced antagonistic or competitive interactions between species in response to higher sediment concentrations compared with lower sediment concentrations mainly in the source region of the river. Differences in the species composition and community diversity of planktonic diatoms were closely correlated with the proportion of bare land area, nitrogen nutrients, precipitation, and sediment concentration. In particular, particle-attached diatoms responded sensitively to environmental factors. These findings provide strong evidence for sediment-mediated assembly and interactions of riverine diatom communities.
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Diatomáceas , Ecossistema , Sedimentos Geológicos , Rios , Rios/microbiologia , Monitoramento Ambiental , China , Biodiversidade , RNA Ribossômico 18S/genéticaRESUMO
Yanhe River Basin is located in the hilly gully area of the Loess Plateau with serious soil erosion. Strong human activities in the middle and lower reaches lead to fragile ecological environment. Soil erosion status varies among different geomorphic units within the watershed (loess liang hilly and gully region, loess mao hilly and gully region, and broken platform region). In this study, we surveyed the benthic community from the Yanhe River Basin in April (spring) and October (autumn) of 2021. To evaluate the water ecological health status of the watershed and investigate the effects of different geomorphic units on the benthic integrity of the benthos, we constructed the benthic-index of biotical integrity (B-IBI) based on the biological data. We identified a total of 113 species of 73 genera in 4 phyla of benthic fauna, with aquatic insects as the dominant taxa in both seasons. Through screening 26 candidate indicators, we found that the spring B-IBI consisted of three indicators: relative abundance of individuals of dominant taxonomic units, family biotic index (FBI), and relative abundance of predator individuals, and that autumn B-IBI was composed of the number of taxonomic units of Ephemeroptera, FBI value, and the relative abundance of predator individuals. Results of the B-IBI evaluation showed that 83.3% of the sampling sites in the upper mainstem and tributaries were at a healthy condition, while only 28.6% sampling sites in the middle and lower mainstem and tributaries were at a healthy condition. In addition, the health status of the watershed was better in spring than in autumn. The Kruskal-Wallis nonparametric tests showed that benthic density, species number, and B-IBI percentile scores in the fragmented loess area were significantly higher in spring than in autumn, and significantly lower in autumn than in the loess liang hilly and gully region and loess mao hilly and gully region, being mainly caused by the increasing erosion due to the concentrated rainfall in wet season. Results of the redundancy analysis showed that key environmental factors affecting benthic community structure in spring were boulder substrate, chlorophyll-a, oxidation reduction potential, turbidity, conductivity, and dissolved oxygen, and were nitrate-nitrogen, oxidation reduction potential, and pH in autumn.
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Ecossistema , Monitoramento Ambiental , Invertebrados , Rios , China , Animais , Monitoramento Ambiental/métodos , Invertebrados/classificação , Invertebrados/crescimento & desenvolvimento , Insetos , Biodiversidade , Estações do AnoRESUMO
To explore the relationship between land use and water quality in basins with different land use patterns at different spatial and temporal scales, the Wuding River Basin and Yanhe River Basin were taken as research objects. Based on land use data in 2020 and water quality monitoring data during two periods, the redundancy analysis method was adopted to quantitatively explore the impact of land use on water quality at multiple scales. The results showed thatï¼ â The main land use types in the two basins were cultivated land and grassland, and the difference was mainly in the proportion of bare land and forest land. â¡ The water quality in spring was better than that in autumn, and the water quality in the middle and lower reaches was worse. ⢠The interpretation rate of land use on the riparian scale was the highest in the two basins. ⣠The effect of land use on water quality was more significant in the Wuding River Basin in autumn than in spring, whereas the Yanhe River Basin showed the opposite trend. ⤠Different land uses had different impacts on water quality. Bare land, cultivated land, and Shannon diversity index ï¼SHDIï¼ in the Wuding River Basin had significant impacts on water quality, whereas grassland, cultivated land, artificial surface, patch density ï¼PDï¼, and SHDI were significant in the Yanhe River Basin. Cultivated land and artificial surfaces in the Wuding River Basin had a negative impact on water quality. Grassland and bare land had a negative correlation with most chemical indicators. Artificial surfaces and grasslands in the Yanhe River Basin had a negative impact on water quality, whereas forest land had a significant purification effect. The research results provide important information for sustainable land use and multi-scale landscape planning, which can be used to improve water quality.
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Uncovering the mechanisms underlying phytoplankton community assembly remains a major challenge in freshwater ecology. The roles of environmental filtering and spatial processes in shaping phytoplankton metacommunity in Tibetan floodplain ecosystems under various hydrological conditions are still unclear. Here, multivariate statistics and a null model approach were used to compare the spatiotemporal patterns and assembly processes of phytoplankton communities in the river-oxbow lake system of Tibetan Plateau floodplain between non-flood and flood periods. The results showed that phytoplankton communities had significant seasonal and habitat variations, with the seasonal variations being more remarkable. Phytoplankton density, biomass, and alpha diversity were distinctly lower in the flood than non-flood period. The habitat differences (rivers vs. oxbow lakes) in phytoplankton community were less pronounced during the flood than non-flood period, most likely due to the increased hydrological connectivity. There was a significant distance-decay relationship only in lotic phytoplankton communities, and such relationship was stronger in the non-flood than flood period. Variation partitioning and PER-SIMPER analysis showed that the relative role of environmental filtering and spatial processes affecting phytoplankton assemblages varied across hydrological periods, with environmental filtering dominating in the non-flood period and spatial processes in the flood period. These results suggest that the flow regime plays a key role in balancing environmental and spatial factors in shaping phytoplankton communities. This study contributes to a deeper understanding of ecological phenomena in highland floodplains and provides a theoretical basis for floodplain ecosystem maintenance and ecological health management.
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The health risk caused by metal pollution is a global concern due to potential metal bioaccumulation, toxicity, and carcinogenicity with multiple sources and pathways. Here, the factors influencing metal bioaccumulation in more than a thousand fish individuals were investigated along a 5464 km continuum of the heavily sediment-laden Yellow River and the health risks to humans were evaluated. The average concentrations of Cr, Zn, As, Cu, Cd, and Pb were below the permissible limits established by domestic and foreign organizations. The fish showed biomagnification of Se and Sn through trophic transfer and a growth dilution effect for V, Mn, Co, Ni, Cu, Zn, As, Cd, and Ba. The concentrations and distributions of most metals in fish were mainly influenced by the trophic levels (δ15N) of fish and the content of the metals in the aquatic environment. The consumption of fish from the Yellow River does not pose a noncarcinogenic risk to the health of adults and juveniles. Cr and As could cause carcinogenic risks, and Cd and Pb also have carcinogenic risks, but these were within an acceptable range. The carcinogenic risks of fish consumption were relatively low in regions with low levels of metal pollution, such as the source region, while the risks were high in regions with heavy pollution and carnivorous fish at high trophic levels. In response to this threat, people can minimize these risks by adjusting their diet and appropriately reducing their consumption of aquatic products from the Yellow River.