Alterations of gut microbiota and short-chain fatty acids induced by Balantidium polyvacuolum in the hindgut of Xenocyprinae fishes providing new insights into the relationship among protozoa, gut microbiota and host.

Introduction: Parasitic ciliates are protozoans with a global distribution. Along with the gut microbiota, they have formed a micro-ecosystem that affects the host's nutrition, metabolism, and immunity. The interactions and relationships among the three components of this microecosystem (protozoa, gut microbiota, and host) remain only partially understood. Xenocypris fish and the unique ciliate Balantidium polyvacuolum in its hindgut are good materials to study the interplay. Methods: In this study, 16S rRNA gene amplicon sequencing and short-chain fatty acids (SCFAs) identification were used. Network was also constructed to understand their relationships. Results: We found that the gut microbiota of B. polyvacuolum-infected X. davidi and X. argentea had higher diversity, richness, and evenness than uninfected ones. B. polyvacuolum could lead to an increase of Fusobacterium and Chloroflexi in both X. davidi and X. argentea, while significantly increase the abundance of genera Romboutsia and Clostridium in X. argentea. Besides, B. polyvacuolum could significantly increase the content of total SCFAs and acetic acid in X. davidi and increase the concentrations of propionic, isobutyric and butanoic acids in X. argentea. Furthermore, correlation analyses showed that B. polyvacuolum may alter SCFAs by affecting key SCFAs-producing bacteria such as Clostridium and Cetobacterium. Discussion: This study greatly expands our understanding of relationships among B. polyvacuolum, gut microbiota and host Xenocypris fish, which sheds new insights into the mechanism of interaction among protozoa, gut microbiota and host.

The energy metabolism of Balantidium polyvacuolum inhabiting the hindgut of Xenocypris davidi.

Anaerobic parasitic ciliates are a specialized group of ciliates that are adapted to anoxic and oxygen-depleted habitats. Among them, Balantidium polyvacuolum, which inhabits the hindgut of Xenocyprinae fishes, has received very limited scientific attention, so the molecular mechanism of its adaptation to the digestive tract microenvironment is still unclear. In this study, transmission electron microscopy (TEM) and single-cell transcriptome analysis were used to uncover the metabolism of B. polyvacuolum. Starch granules, endosymbiotic bacteria, and multiple specialized mitochondrion-related organelles (MROs) of various shapes were observed. The MROs may have completely lost the electron transport chain (ETC) complexes I, III, IV, and V and only retained succinate dehydrogenase subunit A (SDHA) of complex II. The tricarboxylic acid (TCA) cycle was also incomplete. It can be inferred that the hypoxic intestinal environment has led to the specialization of the mitochondria in B. polyvacuolum. Moreover, carbohydrate-active enzymes (CAZymes), including carbohydrate esterases, enzymes with a carbohydrate-binding module, glycoside hydrolases, and glycosyltransferases, were identified, which may constitute evidence that B. polyvacuolum is able to digest carbohydrates and starch. These findings can improve our knowledge of the energy metabolism and adaptive mechanisms of B. polyvacuolum.

Characteristics of fish community structure and environmental driving factors in Taihu Lake during the first year of fishing ban.

Taihu Lake has officially implemented the full fishing ban policy since October 1, 2020. We investigated fish community of Taihu Lake in the four seasons of 2020. A total of 42 fish species were collected, belonging to 6 orders, 7 families, and 33 genera. The first five dominant species ranked by the index of relative importance were Coilia nasus, Toxabramis swinhonis, Hypophthalmichthys molitrix, Hypophthalmichthys nobilis, and Salangichthys tangkahkeii. The number of C. nasus accounted for 85.1% of the total number of catches. According to the distributional characteristics of cyanobacterial blooms and aquatic plants, Taihu Lake could be divided into the northern, central, and eastern regions. There was no significant difference in catch per unit effort (CPUE) among different lake regions, but Shannon diversity index and Pielou evenness index in the eastern region was greater than in the other two regions. The CPUE, Shannon diversity index, and Pielou evenness index were significantly different among the four seasons, with the lowest CPUE in autumn and higher diversity in autumn and winter than in spring and summer. Electrical conductivity, water depth, chloride, and transparency were the main environmental factors driving the seasonal variations of fish community in Taihu Lake, while electrical conductivity, dissolved oxygen, total alkalinity, and transparency were key variables driving the spatial patterns. The results could be used as the baseline data for fish community studies in Taihu Lake after the fishing ban.

A review of PFAS adsorption from aqueous solutions: Current approaches, engineering applications, challenges, and opportunities.

Per- and polyfluoroalkyl substances (PFAS) have drawn great attention due to their wide distribution in water bodies and toxicity to human beings. Adsorption is considered as an efficient treatment technique for meeting the increasingly stringent environmental and health standards for PFAS. This paper systematically reviewed the current approaches of PFAS adsorption using different adsorbents from drinking water as well as synthetic and real wastewater. Adsorbents with large mesopores and high specific surface area adsorb PFAS faster, their adsorption capacities are higher, and the adsorption process are usually more effective under low pH conditions. PFAS adsorption mechanisms mainly include electrostatic attraction, hydrophobic interaction, anion exchange, and ligand exchange. Various adsorbents show promising performances but challenges such as requirements of organic solvents in regeneration, low adsorption selectivity, and complicated adsorbent preparations should be addressed before large scale implementation. Moreover, the aid of decision-making tools including response surface methodology (RSM), techno-economic assessment (TEA), life cycle assessment (LCA), and multi criteria decision analysis (MCDA) were discussed for engineering applications. The use of these tools is highly recommended prior to scale-up to determine if the specific adsorption process is economically feasible and sustainable. This critical review presented insights into the most fundamental aspects of PFAS adsorption that would be helpful to the development of effective adsorbents for the removal of PFAS in future studies and provide opportunities for large-scale engineering applications.

Hydrology and water quality shape macroinvertebrate patterns and facilitate non-native species dispersals in an inter-basin water transfer system.

Understanding biotic assemblage variations resulting from water diversions and other pressures is critical for aquatic ecosystem conservation, but hampered by limited research. Mechanisms driving macroinvertebrate assemblages were determined across five lakes along China's South-to-North Water Diversion Project, an over 900-km water transfer system connecting four river basins. We assessed macroinvertebrate patterns from 59 sites in relation to water quality, climatic, spatial, and hydrologic factors. Macroinvertebrate density, biomass, and species richness increased from upriver to downriver lakes, and were higher during the water transfer period than in the non-water transfer period. Non-native species including Nephtys sp., Paranthura japonica, Potamillacf acuminata, Capitekkidae spp. and Novaculina chinensis, were distributed along the entire study system, some become dominant in upriver lakes. High species turnover occurred in two upriver lakes. Hydrology and water quality are critical factors in shaping these macroinvertebrate patterns. Hydrological disturbance by water transfer boosted macroinvertebrate abundance during the water transfer period while facilitated non-native species dispersals and increased biotic homogenization. This study indicates the need for: 1) an effective ecosystem monitoring system; 2) unified system management standards; 3) external pollution controls; and 4) limiting the dispersal of non-native species.

Land use, hydrology, and climate influence water quality of China's largest river.

Influences of multiple environmental factors on water quality patterns is less studied in large rivers. Landscape analysis, multiple statistical methods, and the water quality index (WQI) were used to detect water quality patterns and influencing factors in China's largest river, the Yangtze River. Compared with the dry season, the wet season had significantly higher total phosphorus (TP), chemical oxygen demand (COD), total suspended solids (TSS), and turbidity (TUR). The WQI indicated "Moderate" and "Good" water quality in the wet and dry seasons, respectively. Compared with other sites, the upper reach sites that immediately downstream of the Three Gorges Dam had lower TP, TN, TSS and TUR in both seasons, and had lower and higher water temperature in the wet and dry seasons, respectively. Water quality patterns were mainly driven by heterogeneity in land use (i.e., wetland, cropland, and urban land), hydrology (i.e., water flow, water level), and climate (i.e., rainfall, air temperature). Water quality in the wet season was primarily driven by land use while the joint effect of land use and hydrology primarily drove in the dry season. Decision-makers and regulators of large river basin management may need to develop programs that consider influences from both human and natural drivers for water quality conservation.

Climate, hydrology, and human disturbance drive long-term (1988-2018) macrophyte patterns in water diversion lakes.

Macrophytes are affected by many natural and human stressors globally but their long-term responses to these multiple stressors are not often quantified. We employed remote sensing and statistical tools to analyze datasets from both short-term (2017-2018) field investigations to explore seasonal patterns, and long-term (1988-2018) Landsat remote-sensing images to detect annual patterns of macrophyte distributions and study their responses to changes in climate, hydrology, and anthropogenic activities in a chain of water diversion lakes in eastern China. We found: 1) biomass and species richness of macrophytes peaked in summer with dominant species of submerged macrophytes Ceratophyllum demersum, Potamogeton pectinatus, and Potamogeton maackianus and floating macrophytes Trapa bispinosa, and non-native species Cabomba caroliniana spread in midstream Luoma Lake and Nansi Lake in summer, while Potamogeton crispus was dominant in all the lakes in spring; 2) water physicochemical parameters (chloride and water depth), lake characteristics (area and water storage), climate factors (air temperature and precipitation), and anthropogenic activities (commercial fishery and urban development) were significantly correlated to the seasonal distribution of macrophytes; 3) long-term data showed a significantly negative correlation between coverage of floating macrophytes and precipitation where the wettest year of 2003 had the lowest coverage of floating macrophytes; and 4) climate (air temperature) and hydrology (water level) were positively correlated with total macrophyte coverage, but human disturbance indexed by the gross domestic product was negatively driving long-term coverage of macrophytes. Our study has important implications for understanding the long-term succession of macrophytes under both natural and human stressors, and for future environmental management and ecological restoration of freshwater lakes.

Can top-down effects of planktivorous fish removal be used to mitigate cyanobacterial blooms in large subtropical highland lakes?

Removal of planktivorous fish is used extensively in northern temperate lakes to reduce phytoplankton abundance via enhanced zooplankton grazing. However, whether this method would work also in large subtropical highland lakes to alleviate cyanobacterial blooms is unknown. We conducted a one-year pilot in situ experiment where we removed a substantial biomass of fish in a fenced-in area, followed by a 3-year whole-lake experiment where the dominant fish species (Japanese smelt) was removed in Lake Erhai in southwest China. The fencing experiments showed that between July and November, when the biomass of the removed stock reached 4 g/m2, the zooplankton biomass inside the fence increased significantly compared to a control fence. In the full-lake experiment, we found that sustained removal of Japanese smelt led to an increase in the biomass of cladocerans (Daphnia spp. but especially of Bosmina spp.) and a significant decrease in the biomass of Cyanobacteria and Chlorophyta. Additionally, a marked increase in the ratio of zooplankton to phytoplankton biomass, as well as an increase in the body size of cladocerans, emphasising the importance of enhanced top-down control for mitigating cyanobacterial blooms following extensive fish removal. Our results reveal that removal of small fish (here Japanese smelt) can lead to a reduction of the phytoplankton and cyanobacteria biomass through a trophic cascade in highland deep subtropical lakes. Thus fish removal may be a feasible additional restoration tool to external nutrient loading reduction in such lakes.

Land conversion induced by urbanization leads to taxonomic and functional homogenization of a river macroinvertebrate metacommunity.

Conversion of forests to urban land-use in the processes of urbanization is one of the major causes of biotic homogenization (i.e., decline in beta diversity) in freshwater ecosystems, threating ecosystem functioning and services. However, empirical studies exploring urban land-use shaping patterns of taxonomic and functional beta diversities and their components in subtropical urban rivers are limited. Here, by leveraging data for 43 sampling sites from urban and forest rivers in Shenzhen, a megacity showing rapid urbanization, we determined the spatio-temporal dynamics and associated drivers of taxonomic and functional beta diversities of river macroinvertebrates. Our results showed that, from the forest to urban rivers, taxonomic beta diversity (wet: 32.9%; dry: 17.1%) declined more significantly than functional beta diversity (wet: 17.4%; dry: 9.5%) in different seasons. We further found that these compositional changes were largely driven by decreased roles of species/traits replacement. Although replacement was also dominant for taxonomic beta diversity (60.4%-68.4%) in two sets of rivers, richness difference contributed more to functional beta diversity in the urban river (52.6%-60.5%). Both deterministic and stochastic processes simultaneously affected beta diversity, with stochastic processes being more important in the urban (3.0-19.0%) than forest rivers (0.0%-3.0%). Besides, db-RDA and variation partitioning results showed that local-scale environmental variables explained considerably large fractions of variation in beta diversity. We hence recommended that biodiversity conservation should focus on improving and restoring local environmental conditions. Despite no significant seasonal differences in beta diversity were detected in this study, we found that the roles of deterministic (i.e., local-scale and land-use variables) and stochastic processes varied considerately across seasons. This result highlights the viewpoint that urban river biodiversity monitoring should go beyond one-season snapshot surveys. As the ongoing trend of urbanization in developing countries, the findings of this study are relevant in guiding urban river environmental monitoring, biodiversity conservation and land-use planning.

Spatial and temporal patterns of heavy metals and potential human impacts in Central Yangtze lakes, China.

Lakes in the central Yangtze River basin have experienced increasing levels of human disturbance during the past several decades, yet large-scale environmental patterns in these lakes and their driving factors remain unclear. Herein we examined spatial and temporal patterns of copper (Cu), zinc (Zn), lead (Pb), arsenic (As), and seven other heavy metals from 16 lakes experiencing a gradient of human disturbance. These lakes were divided among six groups: suburban reservoirs (SR), suburban high-aquaculture lakes (SH), suburban low-aquaculture lakes (SL), suburban no-aquaculture lakes (SN), urban aquaculture lakes (UA) and urban no-aquaculture lakes (UN). Spatially, water-column concentrations of Cd, Ni, Co, Mn, Fe, and Al, and sediment concentrations of Ni were significantly lower in SR compared to other lake groups. Except for Al, heavy metal concentrations did not differ between SN and SL lakes in the water-column or sediments. SH lakes exhibited significantly greater concentrations of Cu, Co, Cr, Mn, and Al in the water-column and Zn in sediments compared to SN lakes. UA lakes contained significantly lower concentrations of Zn, Cd, and Al in sediment compared to UN lakes, though no significant differences were detected within water-column samples. Temporally, with all lake groups combined, summer water-column concentrations of Cd, Pb, Co, Mn, and Al were lower compared to spring and autumn. Additionally, summer sediment concentrations of Zn, As, Co, Fe also were lower compared to autumn. Further results indicated that low-density fish stockings without external feed inputs appeared to have little impact on heavy metals in both suburban and urban lakes. However, high-density fish stockings with external feed inputs were associated with increased heavy-metal concentrations across all lakes. Overall, urbanization has great potential to increase sediment heavy-metal ecological risks. These findings are crucial for developing heavy-metal pollution control and management strategies for freshwater lakes.

Application of Sigma metrics in the quality control strategies of immunology and protein analytes.

BACKGROUND: Six Sigma (6σ) is an efficient laboratory management method. We aimed to analyze the performance of immunology and protein analytes in terms of Six Sigma. METHODS: Assays were evaluated for these 10 immunology and protein analytes: Immunoglobulin G (IgG), Immunoglobulin A (IgA), Immunoglobulin M (IgM), Complement 3 (C3), Complement 4 (C4), Prealbumin (PA), Rheumatoid factor (RF), Anti streptolysin O (ASO), C-reactive protein (CRP), and Cystatin C (Cys C). The Sigma values were evaluated based on bias, four different allowable total error (TEa) and coefficient of variation (CV) at QC materials levels 1 and 2 in 2020. Sigma Method Decision Charts were established. Improvement measures of analytes with poor performance were recommended according to the quality goal index (QGI), and appropriate quality control rules were given according to the Sigma values. RESULTS: While using the TEaNCCL , 90% analytes had a world-class performance with σ>6, Cys C showed marginal performance with σ<4. While using minimum, desirable, and optimal biological variation of TEa, only three (IgG, IgM, and CRP), one (CRP), and one (CRP) analytes reached 6σ level, respectively. Based on σNCCL that is calculated from TEaNCCL , Sigma Method Decision Charts were constructed. For Cys C, five multi-rules (13s /22s /R4s /41s /6X , N = 6, R = 1, Batch length: 45) were adopted for QC management. The remaining analytes required only one QC rule (13s , N = 2, R = 1, Batch length: 1000). Cys C need to improve precision (QGI = 0.12). CONCLUSIONS: The laboratories should choose appropriate TEa goals and make judicious use of Sigma metrics as a quality improvement tool.

A holistic assessment of water quality condition and spatiotemporal patterns in impounded lakes along the eastern route of China's South-to-North water diversion project.

Water quality is one of the key determinants for assessing effectiveness and success of water diversions, but rarely studied at a spatial scale that crosses large river basins. Multiple statistical methods and the water quality index (WQI) were used to assess overall condition and detect spatiotemporal patterns of water quality in a series of impounded lakes along the Eastern Route of China's South-to-North Water Diversion Project. Principal components analysis and analysis of variances identified three groups with distinct water quality characteristics: upstream Gaoyou Lake and Hongze Lake showing relatively higher nutrients, turbidity, and total suspended solids; downstream Dongping lake and Donghu Lake showing higher conductivity, total hardness, and chloride; and Luoma Lake and Nansi Lake intermediate between the two former groups. The WQI indicated overall "Good" water quality with an improving trend from upstream to downstream lakes. The upstream Gaoyou Lake had over 55% of the monitoring sites with "Moderate" water quality in all the seasons. Management should focus on preventing high nitrogen, phosphorus, turbidity, and total suspended solids in upstream lakes, high chloride in downstream lakes, high nitrogen during water diversion seasons, and high phosphorus during non-water diversion seasons. These findings greatly improved our understanding of the spatiotemporal water quality patterns of the impounded lakes, and can be used to develop water quality management strategies. This study exemplifies a methodology for investigating and securing water quality for inter-basin water transfer projects.

Patterns of fish communities and water quality in impounded lakes of China's south-to-north water diversion project.

Understanding the ecological impacts of large-scale hydraulic projects is critical for maintaining ecosystem health while meeting human water needs. It is, however, currently hindered by a lack of direct evidence on ecological impacts associated with this type of project particularly on water quality and fish communities. Here, we characterized patterns and variations of fish communities and water quality in five impounded lakes of the Chinese South-to-North Water Diversion Project (SNWDP), with the aim of better understanding potential ecological impacts of inter-basin water transfers. We found that 1) the impacts of water transfer on water quality in the impounded lakes was generally characterized by hydrological parameters (e.g. total suspended solids, turbidity, transparency, chlorophyll a, dissolved oxygen, conductivity and total hardness) in an upstream-downstream direction; 2) increased hydrological connectivity may have favored biological invasion (e.g. Tridentiger bifasciatus) and promoted a potential biotic homogenization among the impounded lakes; and 3) there was a pattern of decreased fish abundance and biomass from the upstream to downstream lakes with fish communities strongly driven by changing water quality patterns across the impounded lakes. These findings improve our understanding of ecological impacts of large-scale hydraulic projects and provide a significant basis for water agencies with similar water transfer systems to optimize their water transfer management in order to minimize ecological impacts.

Challenges to saving China's freshwater biodiversity: Fishery exploitation and landscape pressures.

China has over 1320 freshwater fish species, 877 of which are endemic. In recent decades, over-exploitation and landscape pressures have threatened them and led to a severe aquatic biodiversity crisis. In response, large-scale fishing bans have been promulgated to protect freshwater biodiversity in major Chinese rivers since the early 1980s. Here, we present the historical background and current challenges to the fishing bans. Implementing large-scale fishing bans may help improve China's current freshwater biological resources and biodiversity to some extent. But implementing fishing bans alone is not sufficient to solve the crisis because of shortcomings of the current bans and expanding human pressures in most river basins. Thus, we recommend regulating other anthropogenic pressures, expanding duration and extent of current fishing regulations, establishing a comprehensive monitoring program, and initiating basin-scale ecological rehabilitation. These programs are also needed in other developing countries facing similar biodiversity crises and human pressures.

Eutrophication and heavy metal pollution patterns in the water suppling lakes of China's south-to-north water diversion project.

This study used non-supervised machine learning self-organizing maps (SOM) in conjunction with traditional multivariate statistical techniques (e.g., hierarchical cluster analysis, principle component analysis, Pearson's correlation analysis) to investigate spatio-temporal patterns of eutrophication and heavy metal pollution in the water supplying lakes (i.e., the Gao-Bao-Shaobo Lake, GBSL) of the eastern route of China's South-to-North Water Diversion Project (SNWDP-ER). A total of 28 water quality parameters were seasonally monitored at 33 sampling sites in the GBSL during 2016 to 2017 (i.e., 132 water samples were collected in four seasons). The results indicated that: 1) spatially, the western and south-western GBSL was relatively more eutrophic and polluted with heavy metals; and 2) temporally, the lakes suffered from high risks of heavy metal contamination in spring, but eutrophication in summer while water quality in winter was the best among the four seasons. Two main potential sources of pollution and transport routes were identified and discussed based on the pollution patterns. These findings contributed considerably to providing in-depth understanding of water pollution patterns, as well as potential pollution sources in the water-supplying region. Such understanding is crucial for developing pollution control and management strategies for this mega inter-basin water transfer project.

Storms do not alter long-term watershed development influences on coastal water quality.

A twelve year (2000-2011) study of three coastal lagoons in the Gulf of Mexico was conducted to assess the impacts of local watershed development and tropical storms on water quality. The lagoons have similar physical and hydrological characteristics, but differ substantially in the degree of watershed urban development and nutrient loading rates. In total the lagoons experienced 22 storm events during the period studied. Specifically, we examine (1) whether there are influences on water quality in the lagoons from watershed development, (2) whether there are influences on water quality in the lagoons from storm activity, and (3) whether water quality is affected to a greater degree by watershed development versus storm activity. The two urbanized lagoons typically showed higher water-column nitrate, dissolved organic nitrogen, and phosphate compared with the non-urbanized lagoon. One of the urbanized lagoons had higher water-column chlorophyll a concentrations than the other two lagoons on most sampling dates, and higher light extinction coefficients on some sampling dates. The non-urbanized lagoon had higher water-column dissolved oxygen concentrations than other lagoons on many sampling dates. Our results suggest long-term influences of watershed development on coastal water quality. We also found some evidence of significant storm effects on water quality, such as increased nitrate, phosphate, and dissolved oxygen, and decreased salinity and water temperature. However, the influences of watershed development on water quality were greater. These results suggest that changes in water quality induced by human watershed development pervade despite the storm effects. These findings may be useful for environmental management since they suggest that storms do not profoundly alter long-term changes in water quality that resulted from human development of watersheds.

Effects of Stormwater Pipe Size and Rainfall on Sediment and Nutrients Delivered to a Coastal Bayou.

Pollutants discharged from stormwater pipes can cause water quality and ecosystem problems in coastal bayous. A study was conducted to characterize sediment and nutrients discharged by small and large (< 20 cm and >20 cm in internal diameters, respectively) pipes under different rainfall intensities (< 2.54 cm and > 2.54 cm, respectively). Results showed that large pipes had greater discharge than small pipes. Pollutants concentrations did not vary by pipe size. Large pipes had greater loads of TSS (138.2 vs. 24.0 mg/s), NO3(-) (5.54 vs. 2.74 mg/s), and NH4(+) (0.39 vs. 0.19 mg/s) than small pipes. Neither discharge nor constituents varied by rainfall events. Pipe size may be a useful metric for estimating loads to a system. Nutrient reduction efforts should be directed to reducing the dissolved nutrient pools, while stormwater management efforts should be directed to reducing pipe freshwater discharge volumes that drive constituent loads.