Abstract:Cyanobacterial bloom has become a frequent and problematic feature of many freshwater bodies over a wide geographical area, especially in China. Microcystis species are widely known for their production of the potent hepatotoxins called microcystins (MCs). While the toxicity of MCs on animals, including humans, has been well studied, the biological role of MCs on the organism from which they originate has not been clearly elucidated. In this paper, we summarized MCs production, especially MCs biological function with the development of technology in recent years. We reviewed and discussed the biological role of MCs in four aspects:Serving as allelochemical, involving in photosynthesis, taking part in the wintering and recovery of Microcystis and in the sustaining and formation of Microcystis colonies. In addition, MCs may act as signal molecule inside and outside Microcystis cells, relevant research has also been reviewed. Global climatic change which favour cyanobacterial blooms in eutrophic waters, may also influence the competition between MC-producing and non-MC-producing strains and their dominance. The study on the competition between MC-producing and non-MC-producing strains and the biological role of protein-bound MCs should be focused on for further investigation, fast development of variable-omics would favor the investigation.

Abstract:Hydrolic retention time in an aquatic environment of lake water has long been of interest to biological limnologists because it is very important for determining lacustrine ecosystem health and sensitive to pollution threats. To evaluate the retention time of Lake Taihu, three scenarios are set up according to the measured data of hydrological, meteorological, boundary conditions of water quantity and quality around the lake in 2010, in which the first is the real scheme, the second is the inflow flux multiplier scheme around the lake, and the last is Wangyu River inflow flux multiplier scheme. EcoTaihu Model is adopted to simulate the nutrients conditions in Lake Taihu and its subzones. The results show that under the hydrological, meteorological and the boundary conditions in 2010, an appropriate hydraulic retention time of Lake Taihu is between 150 days and 160 days.

Abstract:"HUANG Fengming et al. Improvement of the ammonium molybdate spectrophotometric method for phosphorus monitoring in freshwater. J. Lake Sci.,2016, 28(6):1404-1410. DOI:10.18307/2016.0626" has been retracted.

Abstract:Lake Taihu is a typical wind-driven lake, and wind plays an important role in process of water exchange and concentration transportation. Based on Environmental Fluid Dynamics Model (EFDC), water age model and conservative dye model were set up to study characteristics of seasonal water age distribution and to further reveal the impacts of the Wangyu River Water Transfer Project and the Xingou River to the Lake Taihu Transfer Project on water age distribution on basis of winds, inflow and outflow, operations of existing water transfer projects. It is concluded that by the numerical test results, water exchange of Lake Taihu is mainly influenced by the monsoons. Water age is comparably larger in the spring and summer, which indicates the water exchange rate in the spring and summer is lower than that in the autumn and winter. Water ages near inflow locations are comparably smaller, and the locations far from the inflows are larger. Water age is smaller when the flow direction is the same as wind direction, while the exchange of water is increased at the same time and on the contrary water exchange is reduced. During operation of the Wangyu River Water Transfer Project, the water ages of the Gonghu Bay and Middle Lake Taihu are basically reduced, and water exchange is increased in the areas. During operation of the Xingou River Water Transfer Project, the water ages of the Meiliang Bay are basically reduced, and water quality is improved in the area. The water exchange of Lake Taihu will be significantly improved with continuous or occasional transfer operations.

Abstract:Many physical, chemical and biological processes that occur within particular environments, including the transport of pollutants, sediments and other materials, are influenced by lake hydrodynamics. The residence time and travel time of these materials are most commonly used to represent the time scale of the physical transport processes and to elucidate associated water quality problems in lakes. The main objective of this study was to investigate the residence time and tracer travel time in Lake Poyang. A 2D hydrodynamic model (MIKE 21) was combined with dye tracer simulations (advection-dispersion equation) to determine the residence and travel time of the lake for various seasons. The results indicate that Lake Poyang exhibits strong but spatially heterogeneous residence time that varies with the different seasons. Generally, the average residence time is shorter than 10 days along the lake's main flow channels due to the prevailing northward flow pattern. Whereas the local topographically controlled flow patterns substantially increase, the residence time in most bays is approximately longer than 300 days with high spatial values. Flushing homogeneity curves show that approximately 80% of the lake area has the residence time varied between a few days and approximately 1 month, and around 20% of the area has the values in the range from several months to several hundred days. The results demonstrate that Lake Poyang is a mixing water system, which can be divided into fast and slow flushing systems in different seasons. Model simulations also reveal that the tracer travel time of Lake Poyang is in the range of 4-32 days across the lake. Depending on the seasonal water level regimes and associated pollutant transport pathways, the travel time from the released sources to the lake outlet Hukou during the summer and autumn (varies between 11-32 days) is four times greater than that under the spring and winter (i.e., 4-8 days). The outcomes of this study provide important information regarding the sustainable management of water quality, water environment and ecosystem for Lake Poyang.

Abstract:Sediment suspension on sediment-water interface caused by dynamic disturbance is the difficult issue in shallow lake eutrophication control. To study the driving force of sediment suspension in Meiliang Bay of Lake Taihu, a set of synchronous, high-frequency data of current, turbidity, wind, wave are obtained using the Acoustic Doppler Velocimeter, Optical Backscatter Sensor, PH-Ⅱ Handheld weather stations, and RBRduo T.D. wave tide gauge. The results show that when the wind speed is less than 3 m/s, the average suspended solid concentration (SSC) on sediment-water interface is approximately 59 mg/L. The bottom shear stresses generated by waves is nearly equal to that generated by currents, where no sediment suspension can be found and the comprehensive shear stress generated by wind-induced waves and currents is less than 0.015 N/m². When the wind speed ranges from 3 to 6 m/s, the average SSC on sediment-water interface is approximately 103 mg/L. The bottom shear stresses generated by waves is greater than that generated by currents in most cases, where a medium amount of sediment is suspended and the comprehensive shear stress generated by wind-induced waves and currents ranges from 0.015 to 0.25 N/m². When the wind speed exceeds 6 m/s and the average SSC on sediment-water interface is approximately 174 mg/L, the wave-generated shear stress plays an absolute leading role in large amount of sediment suspension and the comprehensive shear stress generated by wind-induced waves and currents is larger than 0.25 N/m². The critical shear stress of sediment suspension in Meiliang Bay is approximately 0.015 N/m² while the critical wind speed is 3 m/s.

Abstract:Suspended solid settlement is one of the main transport forms, and plays an important role in lake nutrient release. Thus, study on suspended solid settling velocity is significant to understand the eutrophication. To study the suspended solid settling velocity, this paper takes Lake Taihu as an example. Field 9 days-in situ observations were conducted in Meiliang Bay using Acoustic Doppler Velocity, Optical Backscatter Sensor and PH-ⅡHandheld weather stations. The suspended solid settling velocity was estimated by the balance of settling and diffusive flux, and we analyzed the relationship among wind speed, vertical velocity, suspended solid concentration (SSC) and settling velocity. The results were obtained:(1) the mean settling velocity is 0.0785 mm/s; (2) the vertical velocity and SSC has a great effect on sediment transport in the surface layer; (3) in the bed layer, the relationship among settling velocity, vertical velocity and SSC shows that when the wind speed was higher than 1.5 m/s, the vertical velocity with large fluctuations and high SSC and the settling velocity were slower; when the wind speed was lower than 1.5 m/s, the vertical velocity was slower and the SSC was small, but settling velocity was quicker, which means the more SSC the quicker settling velocity. It reveals the characteristics of suspended solid settlement in large shallow lakes, which is the necessary foundation in further study of pollutants transport, water environmental mathematic and eutrophication.

Abstract:With the help of GIS spatial interpolation, based on the monthly observed data of water yield and phosphorous (P) concentrations in 36 sampling sites in Lake Dianchi, the loading contributions of different P forms was explored and the spatial and temporal patterns of the P concentrations and loadings were revealed in this paper, aiming at providing evidence for water pollution treatment and inner loading control. The results showed:The changes in total phosphorus (TP) concentrations in the water ranged between 0.13 and 0.64 mg/L, among which particulate phosphorus (PP) covered 72.6%, soluble reactive phosphorus (SRP) 12.8%, and dissolved organic phosphorus (DOP) 14%. During 2013 the average annual TP loading was 251 t/a, among PP loading 190 t/a, SRP 26 t/a, and DOP 34 t/a. TP loading in Lake Dianchi was mostly contributed by PP loading, averaging 76%, and secondly by DOP and SRP, averaging 10% and 13%, respectively. There was a significant difference in seasonal distributions in TP concentrations and loadings and in different P forms. The concentration was characterized with a higher value in summer and autumn in contrast to a relatively low value in winter and spring, while the loading was characterized with a higher value in autumn and winter in contrast to that in spring and summer. Thus, to quantitatively assess the loading of PP and SRP as well as their contributions to TP, was of great importance in guiding the control over the inner loading in Lake Dianchi.

Abstract:The estuarine wetland of Luoshi River, which flowed into Lake Erhai in Yunnan Plateau, is used to be studied as a typical research object. Sediment samples in the estuarine wetland of Luoshi River were collected by the cylindrical sediment sampler and taken from the surface layer (0-10 cm). The spatial distributions of the total nitrogen, total phosphorus and total organic matter were analyzed, and did the pollution risk assessment of sediments. The results showed that:The contents of total phosphorus (TP) in the surface sediments ranged from 0.04 to 1.28 g/kg, and the TP spatial distribution characteristics were lower in areaⅠthan areaⅡ, but higher in channelⅠthan channelⅡ. The content of total nitrogen (TN) in the surface sediments ranged from 0.33 to 2.96 g/kg, and the TN spatial distribution characteristics were higher in areaⅠthan areaⅡ, and higher in channelⅠthan channelⅡ. The content of OM in the surface sediments ranged from 32.43 to 233.03 g/kg, and the OM spatial distribution characteristics were lower in areaⅠthan area Ⅱ, and lower in channelⅠthan channelⅡ. Combined evaluation methods with the comprehensive pollution index and organic index to analyze the pollution of the total nitrogen and the total phosphorus in the surface sediments at the estuarine wetland of Luoshi River, results show that the pollution in areaⅠand channelⅠwas medium level, and the pollution in areaⅡand channelⅡwas mild level. The pollution of organic contaminants in channelⅠand channelⅡwas heavy level, and the area Ⅰand areaⅡwas medium level. The spatial distribution of surface sediment at the estuarine wetland of Luoshi River was influenced by the external pollutant, the culture activity and the aquatic plant. Pollution in channel I was mainly sourced by input of nitrogen and phosphorus, and pollution in channel Ⅱ was mainly dominated by organic matter.

Abstract:129 surface sediment samples and the co-occurrence macrozoobenthos samples were collected from Lake Dongting during 2013-2015. Concentrations of six kinds of heavy metal-arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb) and zinc (Zn) in the sediment were measured and the species composition of macrozoobenthos was identified. The results showed that the average concentrations of As, Cd, Cr, Cu, Pb and Zn were 17.2, 2.63, 56.9, 32.4, 38.4 and 96.3 mg/kg (DW), respectively. Based on the field data on the co-occurrence of sediments and macrozoobenthos and the concentrations of heavy metal, the screening level concentration (SLC) approach was induced to preliminarily explore the sediment quality criteria (SQC) recommended values of heavy metal for surface sediments from Lake Dongting. The calculated SQCs of As, Cd, Cr, Cu, Pb and Zn of Lake Dongting were 11.97, 1.13, 42.03, 19.17, 23.63 and 67.54 mg/kg (DW), respectively. These SQC values were compared with those of different countries and regions. It was found that SQCs obtained in this study were close to the median values of the reference data. The SQCs of heavy metal in Lake Dongting came from different derivation methods were comparative. However, there is still some uncertainty when applied the values of SQC derived from screen level concentration approach. One reason responsible for the uncertainty of the SQCs is that the field data used to derive SQCs is limited. In addition of heavy metal pollution, many other factors can affect the distribution of macrozoobenthos, which will lead to relatively biased in the values of SQCs.

Abstract:Nine dissolved taste and odor compounds (T & O), namely DMS, DMDS, DMTS, β-cyclocitral, β-ionone, MIB, GEO, IBMP and IPMP were investigated in three water areas (Lake Shuiguo, Lake Guozheng and Lake Tangling) of Lake Donghu monthly in 2014. According to the changes of the nine T & O compounds and related environmental factors of each month, relationships of these compounds as well as the relationships with environmental factors were analyzed in this study. It was found that the concentrations of the nine T & O compounds were higher in the summer and fall than in the winter and spring. The seasonal concentrations of DMS, DMDS, DMTS, β-cyclocitral and β-ionone were high and their concentrations all surpassed OTC (Over The Count) in the summer, while other T & O compounds made little contributions to the odor problems of Lake Donghu because of their relative low concentrations. Low concentrations of β-cyclocitral and β-ionone can make water smell flavoury while DMS and DMTS contribute fusty smelling, making the main odors that led Lake Donghu smelly. As for the distributions of odors, the yearly concentrations of DMS, DMDS, β-cyclocitral and β-ionone in Lake Guozheng were all lower than that of the other two areas in Lake Donghu. Based on the relative low concentrations of total nitrogen and chlorophyll-a(Chl.a) and the relative low influence of human activities on Lake Guozheng, odor problem in this area is lighter than that of Lake Shuiguo and Lake Tangling. Meanwhile, there were significantly positive correlations between concentrations of Chl.a and the three taste and odor compounds (DMTS, β-cyclocitral and β-ionone), as well as between concentrations of total nitrogen and the two odors (DMDS and DMTS) in the study. Besides, negative correlations were presented in concentration of dissolved oxygen (DO) with DMS and β-cyclocitral, respectively, indicating that low DO concentration induced by decayed algae could aggravate odor problems. To manage the occurrences of taste and odor events in Lake Donghu, it is critical to control the growth of algae.

Abstract:The characteristics of decomposition rate and quantity of amino acids, as well as the change of nitrogen forms, were explored during the process of decomposition of high-density cyanobacterial particles in this study. The results showed that the initial concentrations of particulate amino acids (PAA) were 0.46 mmol/L in natural light group and 0.44 mmol/L in the aphotic group. At the end of the experiment, the PAA was much stable with a concentration of 0.30 mmol/L in natural light group, while decreased dramatically to 0.06 mmol/L in the aphotic group. The degradation rate constants were 0.03916 and 0.17424 d^-1, respectively. The concentration of dissolved amino acids (DAA) was much lower in comparison to PAA in the process of decomposition. In detail, the DAA increased gradually and peaked at 10.94 and 7.94 μmol/L for the two groups, respectively, and then declined to around the initial value in the end of the 21st day. At the beginning of the experiment, PAA accounted for 74%-80% of the total amino acids, then PAA was transformed to DAA and ammonia (NH₄⁺-N) quickly, and finally the NH₄⁺-N was transformed gradually to NO₃^--N by nitrification. Compared with the natural light group, the decomposition of particles in aphotic group was more complete. Algal photosynthesis inhibited the decomposition of cyanobacterial particles in the natural group. Our results demonstrated that amino acids are potential nitrogen sources of phytoplankton and could be demineralized to NH₄⁺-N to support phytoplankton growth during cyanobacterial blooms. Therefore, the decomposition of high-density algal particles plays a key role in the maintenance of cyanobacterial blooms.

Abstract:Small-scale physical experiment in the laboratory has been taken for simulating the effects of Paspalum distichum,Leersia hexandra, Hydrocotyle vulgaris, Ludwigia peploides and Iris pseudacorus on the literal-zone sediment stabilization by collecting sandy soil from lower reaches of Yangtze River and clay from the literal-zone. The results indicated that the reduced degree of porosity and increased proportion of specified particle (diameter <50 μm) of sediments could improve the quality of overlying water. The linear regression model of the improvement of sediment stabilization with five kinds of plant (Paspalum distichum,Leersia hexandra, Hydrocotyle vulgaris, Ludwigia peploides and Iris pseudacorus and fine root parameters (root length density, root surface area density and root weight density) is put forward. The correlations of root parameters of Leersia hexandra,Paspalum distichum, Hydrocotyle vulgaris with the degree of sediment porosity and with the particle diameter have positively linear correlations with slop arranging from 0.006 to 1.727, respectively, while the negative linear correlation of Iris pseudacorus, Ludwigia peploides with slop arranging from -0.091 to -0.011. Improvements of sediment porosity of Iris pseudacorus and Ludwigia peploides were attained to 15% and 9%, respectively, and improvement of particle diameters to 92% and 47%, respectively. The linear equation was used to calculate the plants' root parameter:11.495 and 9.475 cm/cm³ in root length density, 0.368 and 0.294 cm²/cm³ in root surface area density, 1.844 and 0.944 mg/cm³ in root weight density, for root parameters with sediment porosity and with the particle diameter, respectively. The sediment porosity improvements of Leersia hexandra, Paspalum distichum and Hydrocotyle vulgaris were attained to 6%,36% and 1%, and distribution of particle diameter improvement to 16%,17% and -13%, according to linear equation which was calculated with plants' root parameter:1.057, 7.368 and 0.651 cm/cm³ in root length density, 0.033, 0.228 and 0.022 cm²/cm³ in root surface area density, and 0.678, 2.537 and 0.160 mg/cm³ in root weight density, respectively. Five literal-zone plants are all proved to improve sediment stabilization, which repress eutrophication and sediment resuspension caused by soil erosion on lakeshore. Comparably, the effectiveness from high to low are in descending order from Leersia hexandra, Paspalum distichum, Iris pseudacorus, Ludwigia peploides to Hydrocotyle vulgaris.

Abstract:To understanding the carbon budget, our research chose Lake Gaoyang as object and established an estimate method of carbon budget. From September 2011 to August 2012, we analyzed the main path of carbon budget for the Lake Gaoyang in Pengxi River. The main conclusions for the one year are as follows:input carbon fluxes of river transport were 133548.55 t C, output carbon fluxes of river transport were 125651.82 t C, diffusive fluxes of water to air interface were 762.56 t C, diffusive fluxes of water-level-fluctuating zone were 123.74 t C, ebullition fluxes were 0.38 t C, input carbon fluxes of precipitation were 104.58 t C, and net accumulation of carbon fluxes of the Lake Gaoyang were 7114.63 t C. It was mainly in the form of dissolved inorganic carbon. The carbon in the water of the Lake Gaoyang in Pengxi River showed the characteristics of longitudinal transport along the river channel. Lots of carbon went into the uplift air and deposited in Lake Gaoyang from upstream. It may be the main source of greenhouse gases on the water to air interface. As a whole, Lake Gaoyang presents the characteristic of carbon accumulation throughout the year, but some methods remains uncertain for the spatial and temporal heterogeneity of water-gas interface diffusion flux and air release flux. We need more systematic and long-term work to verify or modify.

Abstract:To illustrate pollution characteristics of atmospheric dry and wet phosphorus deposition of reservoir in the typical sand source area and their contribution to the water phosphorus pollution in order to provide scientific basis for governance of the reservoir eutrophication, we set 12 atmospheric precipitation monitoring sites along the reservoir shore in 2014 in Dahekou Reservoir area in sand source areas of Beijing-Inner Mongolia, and collected dry and wet sedimentation samples to determine concentration of total phosphorus (TP) in dry and wet subsidence and to calculate the yearly and monthly fluxes and the annual storage of TP loading. The results showed that atmospheric TP dry and wet deposition had significantly seasonal differences in the study area. The TP dry deposition flux ranged between 4.89-35.76 kg/(km²·month)in the year, and was mainly concentrated in the spring (April) and autumn (October). The maximum of TP dry deposition flux appeared in the most serious sandstorm month of spring (April). Wet deposition was mainly concentrated in the summer (June to August). The maximum of TP wet subsidence flux appeared in the largest rainfall month (August), and its value was 28.88 kg/(km²·month). The TP wet subsidence flux was significantly positively related with rainfall. Atmospheric pollutant load of TP subsidence storage was 0.719 t in 2014, and the ratio of TP pollution load of both Luan River and Tuligen River storage was 51.17% in the same period. They have become one of the important source term of influencing and restricting the phosphorus nutrient levels in Dahekou Reservoir.

Abstract:Currently many studies have been conducted to analyze the impact of urbanization on the change of stream structure. However, most of them have concentrated on some developed areas, but the less developed urban areas have attracted few attentions. Taking Nansi Lake Basin as the investigation area, this study analyzed the change of stream structure during the urbanization process. The change of land surface was firstly extracted by using remote sensing images of 1987, 2000, and 2014. Based on the stream structure data derived from topographic maps in 1980s, 2003 and 2014, this study further analyzed the effect of urbanization on spatiotemporal change of stream structure in 30 years by adopting indicators of quantity, structure and connectivity, respectively. The results show that:(1) The construction land increased by 1568.06 km² during the past 30 years. The area of urban construction land has grown significantly since 2000. The percentage of urban population was 32% in 2012. (2) The whole river length, area and river density percentage have decreased by 135.46 km, 2.75 km² and 0.49 km/km², respectively during the study period. In addition, the impact of urbanization on stream structure varied spatially across the study area. The rivers at the low level experienced more significant change, while the water surface rates increase by 59.79% continuously. (3) Although the spatial pattern of stream remained unchanged, the stream structure varied significantly during the study period. The stability value of river network decreased by 4.30%, and the connection rate and the combination degree fell by 21.82% and 21.62%, respectively. Moreover, the urban expansion intensity has strong-positively impacted on the stream. The study helps in better understanding the impact of urbanization on stream structure at different spatial scales and urbanization levels, as well as to provide a valuable support and reference for stream protection.

Abstract:Lake Wabu, as the largest lake in the Huaihe Catchment, is located on south bank of the middle-reach Huaihe River and serves as a flood storage area in this basin. To eliminate influence of countryside domestic sewage, this paper is to evaluate the water quality based on data at three monitoring sites and four monitoring sections in the Lake Wabu, which data were obtained during a period from October in 2011 to December in 2015. The pollution factors were analyzed by utilizing methods of the single factor pollution evaluation and the Nemerow pollution index with evaluation indicators of permanganate index, total nitrogen, total phosphorus and ammonium nitrogen. The conclusions are as follows. Water in the Lake Wabu is slightly polluted with the Grade Ⅳ, and its main pollution comes from the sources of agriculture and daily life in the basin. Some inflow rivers already are of bad water quality with abundant nitrogen and phosphorus, in which Zhuangmu River is the worst. It is necessary to renovate the basin environment comprehensively and control the effect of the agricultural non-point pollution.

Abstract:Based on the data of the absorption coefficient of colored dissolved organic matter (CDOM) from 24 surface water samples collected from Zhoucun Reservoir in Huaihe Catchment, we analyzed the spatial distribution characteristics of CDOM absorption coefficient, investigated the correlation between CDOM absorption coefficient and environmental parameters, and explored the possible source of CDOM in the reservoir. The samples collected from the reservoir were categorized into three different groups (storage port, transition region and main reservoir area), the absorption coefficients (a(355) and a^*(355)) had a decrease process from the storage port to main reservoir area, while the S value exhibited an increased trend. Meanwhile, significantly negative correlations of the value of S_240-500 were found with a(355) and a^*(355), respectively, which may have implications for the remote sensing estimation of CDOM in this study. A significantly negative correlation between a(355) and dissolved organic carbon (DOC) concentration was conducive to the establishment of DOC remote sensing inversion model, and relationships between a(355) and a_ph(440) implied the potential contribution of phytoplankton metabolism and degradation products to the CDOM pool in the Zhoucun Reservoir. These results on the CDOM analysis made a significant contribution to the management of the Reservoir in the future.

Abstract:Water movement within the groundwater-soil-plant-atmosphere continuum (GSPAC) plays an important role in maintaining energy and nutrient balance in wetland, and water movement is a key to wetland eco-hydrological process. Numerical simulation is an important method for the study of water movement. However there are few examples of numerical simulation on water movement in wetlands, due to the limitation of complicated natural conditions and restricted monitoring methods. In this paper, a typical wetland in Lake Poyang was selected as a study area. One-dimensional vertical numerical model was used to investigate the water movement process through different interfaces and to quantify relationship of the water supply and drainage. The results showed that, (1) the water fluxes through interfaces were in a significant seasonal variation. The rainfall infiltration and the soil water drainage were sensitive to rainfall, which mainly occurred during April and June, taking 65% and 73% of the annual amount (1450 and 1053 mm), respectively. The soil evaporation and vegetation transpiration were related to climatic conditions and the character of plant growth, which were highest in July-August, taking 30% and 47% of their annual amount (176 and 926 mm), respectively. The upward fluxes from deep soil into root zone mainly occurred in June-August, accounting for 76% of the annual amount (609 mm). (2) The water supply and drainage in plant root zone of the wetland were strongly influenced by the seasonal changes of water level of the Lake Poyang. The main water supply of the root zone is rainfall infiltration except for the high water level period (July-September), in which the upward flow from deep soil is the major water source. In the rising water level (rainy seasons of April-June) and low water level (December-March) periods, the main drainage way is via deep leakage. In the high water level period, the vegetation transpiration is the major water discharge. In lake water level recession period, soil water drainage is mainly via vegetation transpiration and soil evaporation. Our study quantified the water transformation relationship through different interfaces in the typical wetland in Lake Poyang and differentiated the soil evaporation and vegetation transpiration. The results help to better understand the water movement in the GSPAC system and the water balance of lake wetlands, which are essential for lake and wetland managements.

Abstract:Pihe River is not only the largest tributary on north bank of the Huaihe River in Anhui Province, but also the important water source area in middle reaches of the Huaihe River. To determine the spatial distribution pattern of fish community and its influenced factors, a field investigation was conducted in six headwater streams of the Pihe River Basin from April to May, 2015. The results showed that (1) a total of 1762 individuals were collected and identified as 19 species representing 7 families in the six headwater streams. Among them, the omnivore species is accounted for 57.9% of the total species, while the carnivore and herbivore only comprised 26.3% and 15.8%, respectively. Zacco platypus was the main dominant species with an index of relative importance of 2471.94. Lepomis cyanellus was the first reported exotic invasion species in this basin. (2) As for the average value per site of the six streams, the species number and individual number of the three west headwater streams were obviously higher than those of the three east headwater streams, but such a tendency was not found as for the weight of fish. (3) Sorensen similarity analyses showed that great similarity of the fish species was detected among the six streams, and there was the relative smaller similarity between high and low altitudes of streams. The detrended correspondence analysis ordination of the six streams was further examined for the accuracy of similarity analyses. (4) Pearson correlation indicated that the fish species number had significantly correlated with local habitat parameters (including altitude, velocity, substrate type, water depth, water wide, and conductivity) and with spatial location parameters (including stream order, link, and D-link). However, the individual number and fish weight were only significantly correlated with the river substrate type of the local habitat parameters. The results of this study can provide important basic data for the protection and management of fish resources in Pihe River Basin.

Abstract:Phosphorus acquisition by algae and the algal growth inhibition governed by submerged macrophytes have been long-term observed, but the general underlying mechanism is not clear. Here, we assembled mesocosms and subjected them to two treatment regimes, one planted with Ceratophyllum demersum and the other unplanted control, to address the causal mechanisms. The results showed that the average concentration of total phosphorus, total dissolved phosphorus and soluble reactive phosphorus in the unplanted control were significantly higher (about 4 folds) than those in system with macrophyte control, but all their observed values changed with time following S-shaped Logistic curves. Additionally, significantly higher values of algal density, quantum yield, total alkaline phosphatase (APA) and bacterial APA were also detected in the control. And the algal alkaline phosphatase, as the predominant component accounted for up to 44.7% of the total APA, was significantly higher than that of bacterial APA. Structural equation modeling indicated that significant positive influence on total APA only occurred in the unplanted control, and C. demersum growth had a significant decoupling effect on the relationship between different forms of phosphorus and APA, algal density, bacteria dynamic and quantum yield. These results suggested that submerged macrophytes have different tactics to govern algal proliferation.

Abstract:Cylindrospermopsis raciborskii,thought to be an originally tropical species, is found to become dominant and even formed blooms in many reservoirs of Guangdong Province. The dominance of this species presents a new threat to the region but little is known about its bloom forming mechanism. With the above reasons, the study aims to determine the factors that may lead to the successful dominance and bloom formation of C. raciborskii. The C. raciborskii filamental length, phytoplankton species composition, and different environmental physico-chemical parameters were examined monthly during the period of November 2014 and October 2015 in Zhenhai Reservoir. Our results showed that C. raciborskii dominated absolutely in the reservoir during the sampling period. Its biomass ranged from 5.9 to 15.5 mg/L, with a mean value of 11.3 mg/L, accounting for nearly 93.5% of the total phytoplankton biomass. C. raciborskii biomass was relatively high from February to June in 2015. The highest levels were recorded in June and the lowest in both October and November. Filamental length of C. raciborskii exhibited an obvious seasonal regularity. Correlation analysis shows a highly significant negative correlation between filamental length of C. raciborski and water temperature. The biomass of C. raciborskii was significant-positively correlated with total nitrogen and total phosphorus, and significant-negatively correlated with the ratio of nitrogen to phosphorus. Further analysis with continuously multiple factors analysis indicated that total phosphorus concentration was the key factor affecting C. raciborskii biomass. We speculate that the strong absorption to phosphorus and the high P-storage capacity of C. raciborskii have played an important role in the seasonal variation of biomass.

Abstract:We investigated benthic macroinvertebrate communities at 147 sites in eight river systems of the Chaohu Basin in April 2013. Community structure and environmental determinants were examined by canonical correspondence analysis. A total of 213 macroinvertebrate taxa from 177 genera, 76 families, 22 orders, 7 classes, 3 phyla were recorded. The benthic macroinvertebrate community structure showed significant spatial difference among the eight river systems. Nanfei River and Shiwuli River were dominated by Oligochaeta, accounting for more than 96% of the total abundance. Oligochaeta and Chironomidae dominated the communities in Pai River, accounting for 47.8% and 41.1% of the total abundance, respectively. Yuxi River, Baishitian River, Zhegao River and Hangbu River were mainly dominated by Gastropoda. SIMPER analysis showed that Limnodrilus hoffmeisteri was the main dominant species in Shiwuli River and Pai River, and Bellamya aeruginosa was the main dominant species in Zhao River, Yuxi River, Hangbu River, Baishitian River and Zhegao River. L. hoffmeisteri and B. aeruginosa dominated the communities in Nanfei River. The Shannon-Wiener, Simpson and Margalef indices showed significant differences among the eight river systems. Low diversity and abundant pollution tolerant species of benthic communities in Nanfei River, Pai River and Shiwuli River were structured by high nutrient loads, while high diversity and sensitive species richness in Hangbu River.

Abstract:We quarterly investigated zooplankton community in five medium-lake shaped reservoirs in Nanjing during 2010-2011 and analyzed their relations to environmental factors. Totally 28 genera of zooplankton belonging to 17 families were recorded. The dominant species were Daphnia galeata, Bosmina spp., Sinocalanus dorrii, Trichocerca spp. and Polyarthra spp.. The annual average abundance of zooplankton in five reservoirs ranged from 72 ind./L to 1401 ind./L. Zooplankton abundance was significantly higher in Hewang Reservoir than in other reservoirs while there was no significant difference among four seasons. The annual average biomass of the zooplankton in five reservoirs ranged from 102 μg/L to 339 μg/L and there was no significant differences in both five reservoirs and in four seasons. The structures of zooplankton community were analyzed in relation to environmental parameters by canonical correspondence analysis. The results showed that the nutrient level, water temperature, water transparency and phytoplankton abundance strongly regulated the zooplankton communities in five reservoirs in Nanjing Ctiy.

Abstract:The research on phytoliths of Phragmites australis in different growth periods and under different humidity, can provide theoretical basis for the reconstruction of paleovegetation and paleoclimate. Eighteen P. australis samples were selected in Lake Nanhu in Changchun City from May to October and along the humidity gradient of aquatic, seasonal waterlogged and mesic habitats. We then extracted and compared the P. Australis phytoliths of stems and leaves from different growth periods and different habitats. First of all, phytolith assemblages in stems and leaves were different markedly. For example, the contents of rondel and some other phytolith (bulliform, lanceolate and elongate) in stems were higher than those in leaves, while the contents of the silicified stomata in stems were significantly lower than those in leaves. Secondly, the phytolith assemblages in leaves and stems differed. The contents of silicified stomata and some large phytoliths in leaves increased, while contents of saddle and rondel in leaves reduced with the growth of P. australis. In contrast, contents of silicified stomata and lanceolate in stems increased firstly and then decreased, while contents of rondel decreased firstly and then increased. In addition, with the growth of plants, the content of elongate increased steadily, while the content of saddle unchanged. Finally, the contents of phytoliths differed under different habitats. For example, the contents of silicified stomata in leaves increased gradually from mesic to aquatic habitats, suggesting that silicified stomata may indicate the humid environment.

Abstract:Palaeoflood slackwater deposits (SWD) of the Holocene and paleoflood indicators were interbeddedly found within the cliff riverbanks at Xianghanqiao profile in the Longmen reach of the Yellow River. Paleoflood SWD was identified by a variety of sedimentological criteria during field investigations and laboratory analysis. A set of four SWD records four paleoflood events individually. These slackwater deposits recorded the extraodinary floods happened between 3200-2800 a B.P. on the Yellow River, by using Optically Stimulated Luminescence dating method in combination with pedostratigraphy correlations. This indicated that the extraordinary floods happened during the dynasties from the Shang to the Western Zhou in Chinese history. The flooding peak stages were estimated with the sediment concentration and the depositional depths of the SWD. The estimated results indicated that the paleoflood peak discharges were between 46280 and 48800 m³/s by using HEC-RAS model. The results provided an important basis for this regional flood control and disaster mitigation project, water resource management, and comprehensive treatment of the ecological environment.

Abstract:Twelve short sediment cores were collected from Lake Lugu to analyze the particle size composition, magnetic susceptibility (χ_lf), metal content and chemical index of alteration (CIA) in this study. Referencing to the ²¹⁰Pb and ¹³⁷Cs dating results, natural factor such as precipitation on the sedimentary characteristics, and human activity records such as agricultural expansion and deforestation, the temporal and spatial variations in sedimentary characteristics of Lake Lugu in recent 150 years and were discussed. The results indicated that the sediments of Lake Lugu were mainly (>80%) composed of clay and fine silt. The fine fractions (such as clay) showed typical positive correlations with χ_lf and CIA. The sedimentary proxies showed similar vertical changes in the cores from different lake areas. Before 1920s, χ_lf and CIA remained low values and the grain size compositions were stable, suggesting weak human disturbance and stable particle input from the catchment. The clay content, χ_lf and CIA increased gradually since 1920s, which were more remarkable change since ca.1970, indicating enhanced erosion of well-weathered and fine-grained topsoil probably relating to intensive agricultural development and deforestation in Lake Lugu Catchment. The χ_lf and CIA tended to decreasing and median grain size increased since around 2002, which suggested decreasing topsoil erosion attributing to the implement of environmental protection measures such as vegetation recovery in the catchment. Study between the sedimentary proxies and instrumental data showed that climate factors such as precipitation had a weaker effect on the sedimentary evolution of Lake Lugu when compared to human perturbation. Spatially, the sedimentary proxies showed obvious heterogeneity. There was higher clay content in the surface sediments in north and south lake areas where they were near the pluvial-alluvial plains. The mean mass accumulation rates were 0.020-0.043 g/(cm²·a) since 1964, which showed higher values in the south Lake Lugu than in the north Lake Lugu. The high accumulation rate in the south lake should be ascribed to a fact that are influenced by inflow and outflow rivers and the strong soil erosion from the south catchment caused by intensive human activities.