Lower Yangtze River Research Articles

Hydrochemical Characteristics and Evolution of Groundwater in the Alluvial Plain (Anqing Section) of the Lower Yangtze River Basin: Multivariate Statistical and Inversion Model Analyses

The alluvial plain (Anqing section) of the lower reaches of the Yangtze River basin is facing increasing groundwater pollution, not only threatening the safety of drinking water for local residents and the sustainable development and utilization of groundwater resources but also the ecological security of the Yangtze River Basin. Therefore, it is necessary to conduct a preliminary analysis on the hydrochemical characteristics and evolution law of groundwater in this area. This study aimed to evaluate potential hydrogeochemical processes affecting the groundwater quality of this area by analyzing major ions in groundwater samples collected in 2019. Compositional relationships were determined to assess the origin of solutes and confirm the predominant hydrogeochemical processes controlling various ions in groundwater. Moreover, factors influencing groundwater quality were evaluated through the factor analysis method, and the control range of each influencing factor was analyzed using the distribution characteristics of factor scores. Finally, reverse hydrogeochemical simulation was carried out on typical profiles to quantitatively analyze the hydrochemical evolution process along flow paths. The Piper trilinear diagram revealed two prevalent hydrochemical facies, Ca-HCO3 type (phreatic water) and Ca-Na-HCO3 type (confined water) water. Based on the compositional relationships, the ions could be attributed to leaching (dissolution of rock salt, carbonate, and sulfate), evaporation and condensation, and cation exchange. Four influencing factors of phreatic water and confined water were extracted. The results of this study are expected to help understand the hydrochemical characteristics and evolution law of groundwater in the alluvial plain (Anqing section) of the lower Yangtze River basin for effective management and utilization of groundwater resources, and provide basic support for the ecological restoration of the Yangtze River Basin.

Occurrence, distribution, and risk assessment of perfluoroalkyl acids in drinking water sources from the lower Yangtze River

The occurrence, spatial distribution, potential sources, and risk assessment of 14 perfluoroalkyl acids (PFAAs), including 11 perfluoroalkyl carboxylic acids and 3 perfluoroalkyl sulfonates acids, were investigated in 21 drinking water sources from the lower Yangtze River in November 2019. The total PFAAs (∑PFAAs) concentrations ranged from 39.3 to 220.3 ng/L, and perfluorooctanoic acid and perfluorooctanesulfonate were predominant with average concentrations of 19.4 and 15.4 ng/L, respectively. The higher ∑PFAAs concentrations in the southern shore and downstream could be attributed to industrial development and surface runoff/tide currents, respectively. Principal component analysis-multiple linear regression revealed that the primary sources of PFAAs were fluororesin coatings/metal plating, surface runoff/textile, effluent discharge/food packaging, and leather/fabrics. Human intake risks of PFAAs were assessed by target hazard quotient (THQ), which showed that human health risks of PFAAs decreased with increasing age, excluding 13–17 years age group. Moreover, the total exposure risks of PFOA/PFOS in all sampling sites to people aged over 18 years calculated based on contribution from drinking water were noted to be at safe level. The results obtained were helpful for improving our understanding of human health risks of PFAAs, and expanding our knowledge on PFAAs in drinking water.

Comparing Wetland Ecosystems Service Provision under Different Management Approaches: Two Cases Study of Tianfu Wetland and Nansha Wetland in China

The largest blue-green infrastructures in industrialized, urbanized and developed regions in China are often multiuse wetlands, located just outside growing urban centers. These areas have multiple development pressures while providing environmental, economic, and social benefits to the local and regional populations. Given the limited information available about the tradeoffs in ecosystem services with respect to competing wetland uses, wetland managers and provincial decision makers face challenges in regulating the use of these important landscapes. In the present study, measurements made by citizen scientists were used to support a comparative study of water quality and wetland functions in two large multiuse wetlands, comparing areas of natural wetland vegetation, tourism-based wetland management and wetland agriculture. The study sites, the Nansha and Tianfu wetlands, are located in two of the most urbanized areas of China: the lower Yangtze River and Pearl River catchments, respectively. Our results indicated that the capacity of wetlands to mitigate water quality is closely related to the quality of the surrounding waters and hydrological conditions. Agricultural areas in both wetlands provided the lowest sediment and nutrient retention. The results show that the delivery of supporting ecosystem services is strongly influenced by the location and use of the wetland. Furthermore, we show that citizen scientist-acquired data can provide fundamental information on quantifying these ecosystem services, providing needed information to wetland park managers and provincial wetland administrators.

Numerical Simulation of Wind Waves and calculation of planning wave factors in the East Taihu Lake, Jiangsu Province, China

Taihu Lake is a large shallow lake in the lower Yangtze River Delta. The wave action in Taihu Lake plays an important role in coastal port construction. In this paper, based on the 10 min average wind speed at 10 m above the water surface recorded hourly from August 14 to August 17, 2014, the SWAN wave model is used to simulate the wind waves of the Taihu Lake in the corresponding period. Due to the lack of long-time series of wave observation data in the project area, the relationship between design wind speed and wind wave is used to calculate wave elements in different return periods. The results show that the strong wind direction and strong wave direction of the East Taihu Lake are NNW. The waves in the proposed Qidu harbor are mainly from the waves outside the permeable breakwater. Under the action of the most unfavorable wave direction NE, the effective wave height of most waters in the harbor is below 0.4m, which can meet the requirements of avoiding waves for fishing boats.

Relationship between rice farming and polygenic scores potentially linked to agriculture in China.

Following domestication in the lower Yangtze River valley 9400 years ago, rice farming spread throughout China and changed lifestyle patterns among Neolithic populations. Here, we report evidence that the advent of rice domestication and cultivation may have shaped humans not only culturally but also genetically. Leveraging recent findings from molecular genetics, we construct a number of polygenic scores (PGSs) of behavioural traits and examine their associations with rice cultivation based on a sample of 4101 individuals recently collected from mainland China. A total of nine polygenic traits and genotypes are investigated in this study, including PGSs of height, body mass index, depression, time discounting, reproduction, educational attainment, risk preference, ADH1B rs1229984 and ALDH2 rs671. Two-stage least-squares estimates of the county-level percentage of cultivated land devoted to paddy rice on the PGS of age at first birth (b = −0.029, p = 0.021) and ALDH2 rs671 (b = 0.182, p < 0.001) are both statistically significant and robust to a wide range of potential confounds and alternative explanations. These findings imply that rice farming may influence human evolution in relatively recent human history.

Perfluoroalkyl acids in surface sediments from the lower Yangtze River: Occurrence, distribution, sources, inventory, and risk assessment

In this study, the occurrence, spatial distribution, potential sources, mass inventory, and ecological risk assessment of perfluoroalkyl acids (PFAAs) in surface sediments from the lower Yangtze River were investigated based on field and laboratory assays conducted in November 2019. The total concentrations of 13 target PFAAs (∑PFAAs) ranged from 13.83 to 20.33 ng/g dw, and perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) were predominant in the surface sediments with average concentrations of 2.89 and 4.07 ng/g dw, respectively. The ∑PFAAs concentrations in pore-water ranged from 23.30 to 58.81 ng/L, and PFOA and PFOS were predominant with mean concentrations of 6.29 and 5.04 ng/L, respectively. The profiles of PFAAs composition in surface sediments showed limited difference. Results of fugacity model revealed that PFOS was in relative equilibrium, whereas PFOA exhibited a diffusion trend from sediments to water body. Correlation analysis and positive matrix factorization demonstrated that the main sources of ∑PFAAs were electroplating and fast-food packaging, degradation products and textile, mixed sources, and PFOA-based products. The mass inventory of ∑PFAAs was estimated to be 1680.72 kg, and the results of ecological risk assessments based on equilibrium partition and species sensitivity distribution methods suggested that the hazards of PFAAs in sediments to local aquatic organisms are low. However, the evaluation methods and control measures of PFAAs in surface sediments are still limited, requiring further research.

Revealing anthropogenic effects on lakes and wetlands: Pollen-based environmental changes of Liangzi Lake, China over the last 150 years

Lakes and wetlands in populated areas have become very vulnerable to pollution and habitat degradation, seriously threatening regional ecological security and socio-economic development. Exploring long-term environmental changes in these systems is essential to reveal the interactions of human activities and catchments, and further to provide valuable reference for current restoration. In this paper, we present paleolimnological data from a short sedimentary core from Liangzi Lake, a typical wetland nature reserve in the middle and lower Yangtze River Basin, China. Multiple sedimentary proxies (principally pollen but also geochemistry and grain size data) combined with historical records were used to establish environmental changes of Liangzi Lake, in both terrestrial and lacustrine aspects, over the last 150 years. Despite the influence of hydrological processes to some extent, our results indicate that the anthropogenic effects (negative and positive) are well recorded by the sedimentary records. The landscape changes of the wider Liangzi Lake wetland can be placed into four stages: less disturbed background (before the 1950s), hydrological regulation (1950s–1960s), intensive reclamation (1970s–1990s), and wetland restoration (starting in the late 1990s). Agriculture and hydrological control were the most important factors in transforming the wetland landscapes, as well as the aquatic ecosystem. The changes in the lake itself could be divided into three main stages: low nutrient levels and unstable hydrologic condition with dominant emergent plants (before the 1960s), rising nutrient levels and a stable water environment with increasing submerged plants (1960s–1990s), and high nutrient and pollution levels with the subsequent adjustment and restoration (after the late 1990s). Our study provides a comprehensive history of environmental changes of a typical inland lake and its surrounding wetland, and may contribute to future wetland conservation in similar regions, as well as pollen-based environmental reconstruction studies.

Interaction between surface water and groundwater in the Alluvial Plain (anqing section) of the lower Yangtze River Basin: environmental isotope evidence

Interaction between surface water and groundwater in the Alluvial Plain (anqing section) of the lower Yangtze River Basin: environmental isotope evidence

The role of evaporite layers in the ore-forming processes of iron oxide-apatite and skarn Fe deposits: Examples from the middle-lower Yangtze River metallogenic Belt, East China

Iron oxide – apatite (IOA) and skarn Fe deposits are important sources of Fe in China. During the Mesozoic, a large number of large IOA and skarn Fe deposits formed in the Middle–Lower Yangtze River Metallogenic Belt (MLYRMB) in a short period. These deposits genetically show a close spatial relationship to Triassic evaporite layers. In this study, the S isotope values of IOA deposits and Fe skarn deposits in the MLYRMB were collected and summarized. Most of the sulfides from Fe deposits have higher S isotope values (5–10‰), and the sulfates have S isotope values (17–21‰) that are similar to those of the evaporite layers (28–30‰), indicating the involvement of the evaporite layers. The effects of the evaporite layers on the mechanism of Fe ore formation are discussed. Evaporite layers are the most important oxidation barrier in the formation of Fe ores, as they can oxidize Fe2+ to Fe3+ in magmatic melts and magmatic-hydrothermal fluids, promoting Fe accumulation. Evaporite layers can also provide Na, Ca, K, Cl, and other agents of mineralization that facilitate the formation and transformation of Fe-bearing fluids and cause the deposits to display large-scale Na and Cl alterations. When sulfate from evaporite layers oxidizes Fe2+ to Fe3+, S6+ is reduced to S2−, becoming a major sulfur source for the formation of either sulfide ores or pyrite deposits after Fe mineralization. Sulfate (gypsum) from evaporite layers could be activated and transferred to the upper or side part of the ore system, forming anhydrite/gypsum ores (veins). Therefore, pyrite, anhydrite, and Fe ores often appear in single deposit.

Water Pollution Characteristics and Source Apportionment in Rapid Urbanization Region of the Lower Yangtze River: Considering the Qinhuai River Catchment

Clarifying the current situation of regional water pollutants and the relationship between pollutants and pollution sources is considered essential for managing the water environment. Water quality identification index (WQI), cluster analysis (CA), positive matrix factorization (PMF), and stable isotope analysis in R (SIAR) were employed to interpret a large and complex water quality data set of the Qinhuai River catchment generated during 2015 to 2019 to monitor of 11 parameters at 29 different sampling sites. WQI analysis indicated that water quality in Qinhuai River catchment is considered to have "moderate pollution," and an improving trend of water quality was observed at the interannual scale. TN was the most deteriorated of all pollution parameters. CA and PMF results on the spatial scale revealed that sampling sites located at downtown of Nanjing and Lishui District or Jangling University town were highly polluted due to the sewage from domestic sewage and business service sewage (28.88%) as well as industrial wastewater (27.43%), while sampling sites located at Hushu Street Administrative District, Ergan River, and Sangan River were slightly polluted by rural domestic wastewater and garbage (28.79%), and agricultural non-point source pollution (24.3%). The middle-lower reaches (Jiangning Development Zone and Moling Street) and middle reaches (Lukou Street Administrative District) were moderately polluted by industrial wastewater (27.25%), sewage from domestic wastewater and business service wastewater (31.62%) as well as inner sources (24.76%). The SIAR results showed that NO3--N was the main nitrogen form, and the NO3--N mainly originated from sewage (61%) and soil (34%) in the Yuntaishan River sub-catchment. These results will aid in the development of measures required to control water pollution in river catchments.

Habitat alteration facilitates the dominance of invasive species through disrupting niche partitioning in floodplain wetlands

AbstractAimExotic species invasion often leads to declines in local and regional biodiversity, particularly in freshwater ecosystems. This biodiversity loss is generally facilitated by human activities such as land cover change and hydrological alternation. Recent advances in stable isotope analysis (SIA) have been highlighted in many studies addressing fundamental issues in invasion ecology, especially in quantifying competition for resources between native and exotic species. However, how anthropogenic disturbance influences trophic relationships among invasive and native species remains poorly understood.LocationMiddle‐lower Yangtze River Region, China.MethodsTo investigate the effects of human disturbance on interspecific trophic interactions, this study compared isotopic niche space and overlap of the introduced red swamp crayfish (Procambarus clarkii) and the native oriental river shrimp (Macrobrachium nipponense) and freshwater snail (Bellamya aeruginosa) in natural and modified wetlands.ResultsBased on carbon and nitrogen SIA, we found ubiquitous niche shifts in macroinvertebrates with increased competition, which might lead to significant niche contraction in modified habitats at both community and population scales. Moreover, the isotopic niche width of the exotic crayfish was twice as larger as that of natives at both habitats, suggesting that the exotic P. clarkii had great competitive superiority over the native species. However, the effects of habitat modification on niche overlap were inconsistent. While the niche overlap between crayfish and shrimp was significantly higher in modified habitats than in natural open waters, niche overlap between crayfish and the snail was significantly reduced.Main conclusionsCollectively, our findings highlight that the competitive outcomes of interspecific trophic interactions can be dependent on the prey availability and diversity, which embraces both the classic optimal foraging theory and competition theory to understand how environmental change, such as habitat alternation, affects the biological invasion processes.

Spatiotemporal Characteristics of Drought in the North China Plain over the Past 58 Years

Understanding the spatiotemporal characteristics of regional drought is of great significance in decision-making processes such as water resources and agricultural systems management. The North China Plain is an important grain production base in China and the most drought-prone region in the country. In this study, the monthly standardized precipitation evapotranspiration index (SPEI) was used to monitor the spatiotemporal variation of agricultural drought in the North China Plain from 1960 to 2017. Seven spatial patterns of drought variability were identified in the North China Plain, such as Huang-Huai Plain, Lower Yangtze River Plain, Haihe Plain, Shandong Hills, Qinling Mountains Margin area, Huangshan Mountain surroundings, and Yanshan Mountain margin area. The spatial models showed different trends in different time stages, indicating that the drought conditions in the North China Plain were complex and changeable in the past 58 years. As an important agricultural area, the North China Plain needs more attention since this region shows a remarkable trend of drought and, as such, will definitely increase the water demand for agricultural irrigation. The strong correlation between these spatial distribution patterns indicates that the climate and weather conditions leading to drought are consistent and that drought conditions are independent for regions that are not correlated. If this trend continues, the characteristics of drought variability in the North China Plain will become more complex, and a more detailed water management strategy will be needed to address the effects of drought on agro-ecosystems. Recognizing the drought variability in the North China Plain can provide a basis for agricultural disaster reduction planning and water resources allocation.

Early cretaceous crust–mantle interaction in the Middle-lower Yangtze River Metallogenic Belt, east China: Li–Nd–Sr isotopic and elemental constraints

The petrogenesis of adakitic rocks and their implications for the crust–mantle interaction remain enigmatic. To provide important insights into these issues, we carried out a detailed investigation of Li–Nd–Sr isotopes and elements for the Early Cretaceous intermediate rocks and related mafic microgranular enclaves (MMEs) from the southwestern Middle–Lower Yangtze River Metallogenic Belt, central eastern China. The intermediate rocks in the Edong district are characterized by high SiO2, MgO, and K2O and low Na2O concentrations of 61.5–66.1 wt%, 0.4–2.3 wt%, 2.8–7.4 wt%, and 2.3–5.5 wt%, respectively, enrichment in LREEs and LILEs (e.g., Sr and La concentrations of 414.99–1619.45 ppm and 20.41–53.88 ppm), and relative depletion in Y (7.84–19.20 ppm) and Yb (0.59–1.73 ppm), endowed with both the high silica adakitic and high-K calc-alkaline affinities. The MME-bearing adakitic rocks exhibit wide ranges of (87Sr/86Sr)i, εNd(t) and δ7Li values (0.7028–0.7087, −8.9 to −3.0 and − 2.0‰ to +9.9‰, respectively), indicating a mixing process between felsic melts from a juvenile lower crust and mafic melts from an enriched mantle source. They were subsequently subjected to significant fractional crystallization of pyroxene and hornblende and minor crustal contamination during the ascent. High Sr/Y and La/Yb ratios, the salient geochemical peculiarities of adakitic rocks, might be inherited from magma sources and then be strengthened by fractionation of ferromagnesian phases. Hybrid magmas with high water content, and high oxygen and sulfur fugacity facilitate Cu ± Mo ± Au polymetallic mineralization. The adakitic rocks and related deposits in central eastern China could be related to upwelling of asthenospheric mantle caused by the subduction of the Paleo-Pacific plate during the Early Cretaceous and its induced reactivation of sub-continental lithosphere. The crust–mantle interaction model is probably applicable to formation of the adakitic rocks worldwide.

Garnet major and trace element evidence of the alteration and mineralizing processes associated with genesis of the Qiaomaishan skarn deposit, Xuancheng ore district, eastern China

The Qiaomaishan deposit is a skarn-type Cu–W deposit located within the Xuancheng ore district of the Middle–Lower Yangtze River Metallogenic Belt of eastern China. The mineralization within the deposit is predominantly located along the contact between a porphyritic granodiorite intrusion and surrounding Carboniferous limestone units. The deposit is associated with a well-developed and zoned skarn system that includes both endoskarn and exoskarn zones. This study presents new garnet major, trace, and rare earth element (REE) geochemical data for these skarn zones, discusses the factors (e.g., crystal chemistry, oxygen fugacity and water/rock interaction) that control the incorporation of trace elements into garnet, and constrains the formation of skarn within the Qiaomaishan deposit. Grossular (Adr21–70Grs29–78; type 1) garnet is generally located within the endoskarn and is light REE (LREE) enriched but heavy REE (HREE) depleted with weakly negative Eu anomalies and higher total REE contents than the exoskarn garnet in the study area. Type 1a grossular garnet is further split from type 1b grossular garnet by the presence of positive Pr and Nd anomalies and high LREE concentrations. Exoskarn garnet has pure andradite compositions and is split into type 2 and 3 garnets, where type 2 andradite garnet has variably positive Eu anomalies and variable total REE contents that are indicative of formation under transitional or oscillating conditions (e.g., pH, oxygen fugacity). In comparison, the type 3 andradite garnet has low total REE contents and positive Eu anomalies. Endoskarn garnet Al2O3 and total REE contents positively correlate, indicating that REE is incorporated into this garnet through coupled YAG-type substitution. The differences between the total REE contents of the type 2 exoskarn and endoskarn garnets may reflect host rock buffering as well as variations in the crystal chemistry of the two garnets present within the different parts of the skarn system (grossular and andradite). In comparison, the differences in the total REE contents of the two types of exoskarn garnet may reflect variations in water–rock ratios and crystal growth rates. The different Eu anomalies and U contents present within the different types of garnets record variations in the pH and oxygen fugacity of the hydrothermal fluid over time. These changes may have promoted the crystallization of magnetite and scheelite and the formation of the tungsten mineralization within the deposit. This study demonstrates the usefulness of garnet in tracking variations in mineralizing conditions and processes and confirms the validity of these minerals as vectors or indicator minerals that can be used in combination with traditional exploration approaches to determine whether a system is mineralized or not during the early stages of exploration.

Sedimentology, geochronology, and provenance of the late Cenozoic “Yangtze Gravel”: Implications for Lower Yangtze River reorganization and tectonic evolution in southeast China

AbstractThe evolution of the Yangtze River, the longest river in Asia, provides a spectacular example for understanding the Cenozoic interaction between tectonics, climate, and surficial processes. The oldest Lower Yangtze deposits, characterized by ~100-m-thick sequences of unconsolidated conglomerate, sandstone, and siltstone, referred to as “Yangtze Gravel,” have been recently dated &amp;gt;23 Ma, indicating a pre-Miocene establishment of a through-going river. However, the link between river integration and tectonic evolution has never been established due to the limited study of these sediments.Here, we report sedimentology, geochronology, and provenance of the Yangtze Gravel based on 17 stratigraphic sections exposed along the Lower Yangtze River. Our new chronostratigraphic results, including 40Ar/39Ar ages from the overlying basalt and fossil-based stratigraphic correlation, suggest an early-middle Miocene age for these sediments. Detailed analysis of lithofacies reveals several sequences of coarse-grained channel-belt deposits (channel fills and bars), indicating braided alluvial deposition across the Jianghan Basin, North Jiangsu-South Yellow Sea Basin, and East China Sea Shelf Basin. This ancient Lower Yangtze River is further characterized by petrography and detrital zircon U-Pb geochronology results which show similar provenance and erosion pattern as the present-day Yangtze River. However, the ancient river in early-middle Miocene is an alluvial, bedload-dominated braided river with higher stream power and a more prolonged course flowing into the East China Sea Shelf Basin. These differences between ancient and modern Lower Yangtze River reflect varied climate and paleogeography in southeast China during the late Cenozoic.Compared with the Paleogene red-colored, halite-bearing, Ephedripite pollen-dominated, lacustrine deposits in Jianghan Basin and North Jiangsu-South Yellow Sea Basin, the deposition of yellow to green-colored, coarse-grained, arboreal pollen, and wood-dominated Yangtze Gravel indicates a drainage reorganization from hydrologically closed lakes to a through-going river system during late Oligocene to early Miocene. During Paleogene, rift basins were filled by alluvial and fluvial-lacustrine deposition with restricted flow distance and local sources. From late Oligocene to early-middle Miocene, the post-rift subsidence opens a path for the ancient Lower Yangtze River connecting the Jianghan Basin, North Jiangsu-South Yellow Sea Basin, and East China Sea Shelf Basin. We attribute the drainage reorganization of the Lower Yangtze River to be a surficial response to Cenozoic tectonics, particularly the western Pacific subduction, in southeast China. The deposition of the widespread, coarse-grained Yangtze Gravel is probably due to the combined effects of catchment expansion and strong monsoonal climate in East Asia.

Using stratified Bayesian model averaging in probabilistic forecasts of precipitation over the middle and lower Yangtze River region

Using stratified Bayesian model averaging in probabilistic forecasts of precipitation over the middle and lower Yangtze River region

Distinct microhabitats affect the relative balance of ecological processes shaping the spatial distribution of bacterial communities in lakeshore habitats

Abstract The lakeshore habitat, which is an interface zone between lake and land, harbours various organic particles providing nutrient‐rich microhabitats for bacterial colonisation. Revealing the mechanisms maintaining the bacterial diversity generated on these particles is vital for understanding the biogeochemical processes within lakeshore habitats. To date, however, the bacterial communities within lakeshore habitats have been rarely explored, and knowledge of the ecological processes associated with their spatial distribution is limited. Here, we employed amplicon‐based high throughput sequencing technology to investigate the composition, co‐occurrence patterns, spatial distribution, and assembly processes of free‐living and particle‐attached bacterial communities (FLBC vs. PABC) across 29 lakeshore zones within freshwater lakes from two typical regions: Middle–Lower Yangtze River Plain and Yunnan–Kweichow Plateau. We found significant community dissimilarity between both bacterial lifestyles and regions. PABC exhibited higher community dissimilarity between the plain and plateau regions than FLBC did. Furthermore, eight operational taxonomic units were detected as a core bacterial community within the lakeshore habitats across the plain and plateau regions. Network analysis revealed that bacterial taxa preferring a particle‐attached lifestyle exhibited more co‐occurrence associations for both intra‐ and inter‐community than the free‐living lifestyle. Both FLBC and PABC showed significant distance–decay relationships in these two regions. Dispersal limitation was the most important process associated with patterns in the spatial distribution of FLBC and PABC, whereas the relative importance of variable and homogeneous selection differed between the assembly of FLBC and PABC because of differences in their microhabitats. Our results highlight that dispersal limitation may be strongly associated with the spatial distribution of lakeshore bacterial communities at a regional scale. However, lifestyle differences influence the relative balance between the processes of dispersal, selection, and biotic interaction that influence these bacterial communities. This study reveals potential interactions between bacterial taxa with different lifestyles as well as indicating which ecological processes may lie behind the spatial distribution of bacterial communities in lakeshore habitats. Knowledge of potential assembly mechanisms of bacterial communities within different microhabitats help us understand how bacterial communities in different microhabitats are generated and their different roles in biogeochemical processes in lakeshore habitats.

Effects of air quality and vegetation on algal bloom early warning systems in large lakes in the middle–lower Yangtze River basin

Studies of algal bloom early warning systems have rarely paid attention to the dynamics of excessive proliferation of phytoplankton (EPP), which occurs prior to algal blooms, or to the sensitivity of a lake to EPP based on multiple environmental factors. In this study, we investigated EPP dynamics in large lakes and identified major factors that influenced the lake's vulnerability to EPP, to improve algal bloom early warning systems. High temporal moderate resolution imaging spectroradiometer (MODIS) images and multi-source daily site monitoring data of large lakes in the middle–lower Yangtze River basin were analyzed. Then, the floating algal index (FAI) and resource use efficiency (RUE) by phytoplankton were used to investigate the EPP dynamics and lake's vulnerability to EPP, respectively. Moreover, generalized linear models were used to assess the relative importance of environmental factors on RUE. The results indicate that the lakes freely connected (FC) to the Yangtze River (Dongting Lake and Poyang Lake) had lower FAIs but higher RUEs than the non-connected lakes (NC; Chaohu Lake and Taihu Lake). The key factors affecting RUE-FC were standard deviation of water level within 30 days(WL30), particulate matter <10 μm(PM10), and relative humidity(Hum), which explained 15.91% of the variations in RUE. The key factors affecting RUE-NC were ozone(O3), basin normalized difference vegetation index standard deviation(BNDVISD), and dissolved oxygen(DO), which explained 35.28% of the variations in RUE. These results emphasize the importance of air quality in influencing or reflecting EPP risks in large lakes. In addition, basin vegetation and hydrological rhythms can influence NH4+ through non-point source loading. Algal bloom early warning systems can be improved by routine monitoring and forecasting of potential environmental factors such as air quality and basin vegetation.

Roles of water vapor sources and transport in the intraseasonal and interannual variation in the peak monsoon rainfall over East China

ERA-Interim reanalysis data from 1979 to 2017 are utilized to analyze the intraseasonal and interannual variabilities in the moisture transport associated with the summer rainfall over East China. Three key issues of moisture sources for East China summer precipitation are discussed in this study: the identification of the primary moisture sources of summer precipitation, determination of their individual contributions to the intraseasonal variation in summer precipitation, and determination of the extent to which each source affects the interannual variation in precipitation during the peak monsoon rainfall period (PMRP). Through the Lagrangian method, the water vapor is divided into six sources, namely, the land area source, East China source (EC source, except for the target region), Indian Ocean source (IO source), Pacific Ocean source, South China Sea source, and regional evapotranspiration sources. This study proposes that the rainfall over South China during the PMRP is mainly influenced by the IO source water vapor transport (52.4%). For the middle and lower Yangtze River valley, the rainfall contribution from southwesterly moisture transport accounts for approximately 50% of the total rainfall during the PMRP and determines the intraseasonal and interannual variation in the summer rainfall. The water vapor from terrestrial evaporation, which includes EC source water vapor (38.9%) and North China (NC) source water vapor (21.8%), is the most important moisture source for rainfall over NC during the PMRP.

New insights to protection and utilization of silver carp (Hypophthalmichthys molitrix) in Yangtze River based on microsatellite analysis

In the present study, fourteen highly polymorphic microsatellite markers were used to analyze genetic diversity and population structure of six populations of silver carp in the middle and lower Yangtze River basin. The results showed that the polymorphic information content (PIC) of these fourteen loci was between 0.306−0.848, 9 of 14 loci were highly polymorphic (PIC > 0.5). The allele number (Na) of the 6 populations was between 5–18, and the effective allele number (Ne) ranged from 1.5628 to 7.2676. The observed heterozygosity and expected heterozygosity were ranged from 0.287 to 0.753, and from 0.361 to 0.865, respectively. The average polymorphism information content was between 0.306 to 0.848. The Jianli, Changsha and Jiaxing population showed relatively high genetic diversity in all six populations(PIC > 0.5). The genetic distance between the Jianli and Hanjiang was the highest, while Ruichang and Jiaxing with the lowest genetic distance. The phylogenetic relation results showed the six populations were clustered into two clades, which indicated that there were differentiated in certain degree among the middle and lower populations in Yangtze river basin and the populations of this research may belong to different spawning grounds. In next enhancement and releasing, the germplasm resources of silver carp should be selected from corresponding regions.