Abstract:Epiphytic community is a complex structure consisting of organisms such as algae,bacteria and fungi,and covers the surface of aquatic macrophytes in most shallow lakes.It has a unique composition and spatial structure,exhibiting significant dynamic characteristics in accordance with different seasons and the growth of submerged plants.Epiphytic community is closely related to the host plants and surrounding water environment,reflecting various habitat factors such as nutrient,light and temperature.It also has different interactions with submerged macrophytes,grazers,phytoplankton and other aquatic organisms.Epiphytic community participates in the material transformation of water ecological system,and plays a vital role in the shift between macrophytedominated and algal-dominated lake ecosystems.Its relatively high primary productivity makes itself to be an important food source for aquatic animals,which results in diverse food webs.Based on previous studies,this article analyzed the species composition and dynamic characteristics of epiphytic community.It can be concluded that epiphytic community is an important component for aquatic ecosystems,and further studies on epiphytic community can provide scientific basis for the restoration of submerged macrophytes in management of eutrophic lakes.

Abstract:This paper focuses on the recent findings of sexual reproduction in monogonont rotifers,which account for the main bulk of phylum Rotifera.Generally,they act as one of the major groups of primary consumers in freshwater ecosystem.Thus,studies on population dynamics and their mechanisms of monogonont rotifers may provide important data to both theoretical and applied research on freshwater ecosystems.As a group with parthenogenetic life history,sexual reproductive strategy in monogonont rotifers may profoundly affect their population dynamics and evolution.This review summarized several aspects of sexual reproduction in the monogonont rotifers,such as the mechanism,pheromones,models,influence factors,and particularly,empirical evidences.More specifically,we emphasized three models about their sexual reproduction patterns: "bang-bang"model,intermediate mictic ratios model and no-delaying mixis model.Then we summarized the exogenous and endogenous factors that affect sexual reproduction.The major exogenous factors include the concentration and type of food,temperature,salinity and special bacteria,while the major endogenous factors include the maternal age,a transgenerational maternal effect induced by food concentration,mixis delay and some potential maternal effects.We especially highlighted the model,mechanism and empirical evidences of mixis delay,since this phenomenon existed widely and was deem to be a potential explanation for species or clones coexistence.We also gave some personal views on the relationship between sex allocation theory and sexual reproduction in the monogonont rotifers.Finally,several potential hotspots in the future study were highlighted.

Abstract:Reconstruction of submerged vegetation is one of the key measures of eutrophication remediation.Using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and clone library analysis,we studied the impact of planting Potamogeton crispus and Vallisneria natans on bacterial diversity and community composition in West Lake,Hangzhou,China.Bacteroidetes (42.9%),Betaproteobacteria (30.8%) and Verrucomicrobia (14.3%) dominated in the water column from lake areas without submerged macrophytes.On the contrast,the proportion of Bacteroidetes reduced to 12.7% and 5.3%,respectively, after planting Potamogeton crispus and Vallisneria natans.Meanwhile,Betaproteobacteria increased to 52.4% and 59.5%,and Alphaproteobacteria increased from 4.4% to 19.0% and 12.8%,respectively.The proportion of Verrucomicrobia reduced substantially after planting Potamogeton crispus,but varied little after planting Vallisneria natans.This study indicates that submerged macrophytes can not only improve water quality,but also increase bacterial diversity,and shape bacterial community composition significantly.

Abstract:The investigation was conducted within large,shallow Lake Taihu,in winter and summer.5 sites in phytoplankton dominated zone and 3 sites in macrophyte dominated zone were chosen for sampling.Parameters of sampling sites including water quality, nutrients concentrations in 5-cm overlaying water and vertical profiles of water content,mean value of grain size (D50),total organic carbon (TOC),nitrogen,phosphorus,metals and dissolved oxygen were analyzed.Results showed that,surface water pH in phytoplankton dominated zone was higher than that in the other two layers and water pH in winter was higher in macrophyte dominated zone than that in phytoplankton dominated zone;water nephelometric turbidity unites in macrophyte dominatd zone was higher than those in phytoplankton dominated zone in summer and contrarily in winter;concentrations of NO₃^--N and PO₄^3--P of overlaying water were significantly higher in phytoplankton dominated zone than those in macrophyte dominated zone;sediment water contents in macrophyte dominated zone in winter was significant higher than those in summer;sediment TOC in macrophyte dominated zone was significant higher than that in phytoplankton dominated zone.There was significant difference of sediment metal concentration,including Fe,Zn,Ca,Pb,Na and K between macrophyte and phytoplankton dominated zone;oxygen penetration depths were deeper in winter than those in summer,and in phytoplankton dominated zone than in macrophyte dominated zone.

Abstract:Eutrophication under climate warming is a hot topic in limnology recently.Our study demonstrated that epilimnetic total phosphorus (TP),total nitrogen (TN) and air temperature increased with the process of eutrophication in Lake Erhai in 1980-2009.Statistics analysis demonstrated that,air temperature promoted the growth of phytoplankton with no effect from TP and TN, TP promoted the growth of phytoplankton with no effect from air temperature but with effect from TN,TN promoted the growth of phytoplankton with no effect from air temperature and TP individually but with effect from their interaction.Climate warming and nutrient enrichment promote eutrophication of Lake Erhai together.

Abstract:An investigation of Microcystis aeruginosa colony diameters in different water depths and locations was carried out monthly in the protection zone of water source region of Chaohu City from April to August,2011.The spatio-temporal distribution characteristics of the colony diameter were summarized using statistical analysis.The M.aeruginosa colony appeared between mid-April and mid-May,there was significant difference between the surface layer and lower-middle layers on colony diameters at both sampling sites of S1 and S2.Colonies with diameters less than 200 μm distributed vertically homogeneously in the water column,colonies with diameters between 200 μm and 800 μm tended to gather in the water surface,and colonies with diameters greater than 800 μm were apt to aggregate in the bottom layer.The level of colony diameter of outer sampling site (S2) was higher than that of inner sampling site (S1) in each month.Because the colony diameters were easily affected by the short-term meteorological condition, the variance of colony diameters didn't show conspicuously regular monthly.There was no significant difference in the spatial distribution of colony shape,while it shifted gradually from elongated to regular with seasons changing.The distribution range of colony diameters indicated that,in theory,99.81% of the total M.aeruginosa colonies can be filtered by the large bionic equipment for clearing cyanobacteria.

Abstract:Nitrate (NO₃^--N) and ammonium (NH₄⁺-N) are two major inorganic nitrogen forms in eutrophic water.Study on NO₃^--N and NH₄⁺-N uptake kinetics of aquatic plants can help to find the hydrophytes that efficient removal of nitrogen in eutrophic water.The nutrient uptake kinetics of Iris louisiana,Myriophyllum verticillatum,Zizania latifolia and Oenanthe clecumbens were investigated using the concentration gradient method after plants were grown for 15 days in Hogland nutrition liquid.Results showed that NO₃^--N and NH₄⁺-N uptake kinetics of the 4 species could be expressed by the Michaelis-Menten equation.The NO₃^--N and NH₄⁺-N uptake rates of hydrophytes enhanced with increasing NO₃^--N and NH₄⁺-N content;however,when the solution increased to 2.0 mmol/L,the increasing amplitude of the uptake rates would reduce.The maximum rate (V_max) of uptake NO₃^--N and NH₄⁺-N by the 4 species of hydrophytes followed the order: Oenanthe clecumbens > Zizania latifolia > Iris louisiana > Myriophyllum verticillatum.The chemical affinity(K_m) of NO₃^--N followed the order: Oenanthe clecumbens > Iris louisiana=Zizania latifolia=Myriophyllum verticillatum.The K_m of NH₄⁺-N followed the order: Oenanthe clecumbens > Myriophyllum verticillatum > Iris Louisiana=Zizania latifolia.According to parameters(V_max,K_m) of uptake kinetics,as a conclusion,Oenanthe clecumbens is suitable for purifying high NO₃^--N and NH₄⁺-N content waters,but Zizania latifolia,Iris louisiana and Myriophyllum verticillatum are just opposite.The four hydrophytes have showed different preferences of uptake NO₃^--N and NH₄⁺-N form solution.The potential of uptake NO₃^--N form solution by Iris louisiana was higher than that of uptake NH₄⁺-N,but the chemical affinity of uptake NH₄⁺-N was higher than that of uptake NO₃^--N,this show that Iris louisiana preferentially uptake NH₄⁺-N from high NO₃^--N content water.Myriophyllum verticillatum and Oenanthe clecumbens are equivalent in absorbing NO₃^--N and NH₄⁺-N.Zizania latifolia showed higher potential and chemical affinity of uptake NH₄⁺-N than NO₃^--N.

Abstract:Lake Poyang catchment,a large scale system with high spatial variability in land surface characteristics,was chosed to be the study area in this paper.Catchment hydrological and lake hydrodynamic processes are the main processes in the system.To represent the interaction of hydrological and hydrodynamic processes between the lake-catchment and reflect the mechanisms for different processes,an integrated model was set up.The integrated model used three sub-models with different functions to perform spatial linkage and it included a catchment distributed hydrological model WATLAC,a lakeside plain area runoff model and a lake hydrodynamic model MIKE 21.The integrated model used an input-output linkage approach and involved sequential execution of individual sub-model,i.e.,the discharges of major rivers and runoff of plain area were used as input conditions to drive the lake hydrodynamic model,and thus simulate the lake water level in response to catchment discharges.We used the river discharges of six hydrological stations and average base flow index as well as water levels of four lake stations as state variables to calibrate the integrated model.The Nash-Sutcliffe efficiency (E_ns) and determination coefficients (R²) of daily river discharges vary from 0.71-0.84 and 0.70-0.88,respectively and vary from 0.88-0.98 and 0.96-0.98 for lake water levels.Results indicate that the integrated model can ideally reproduce the response of lake water level to the catchment rainfall-runoff process.The simulated lake lev-els further demonstrate that the integrated model has the ability to obtain the detailed hydrodynamic characteristics in space and time.The proposed model can be used as an effective tool to quantitatively reveal the hydrological and hydrodynamic processes of lake-catchment system in response to climate change and human activities in the catchment.

Abstract:SWAT model and measured data were used to simulate the Non-Point Source (NPS) N and P pollution from 2001 to 2010 in Lake Nansi watershed.The spatial distribution of the pollution was analyzed,and the contribution of all the rivers in watersheds to the pollution of Lake Nansi were calculated.The key areas with serious pollution were distinguished.The results indicated that: (1) typical watersheds were simulated with SWAT model,and then the derived models were used to simulate the Lake Nansi watershed.This method can not only improve efficiency,but also with higher simulation accuracy.The simulation results in the east of the lake were better than those in the west part of the lake,which indicated that SWAT model was suitable for the hilly areas.(2) The NPS pollution was serious in Lake Nansi watershed.The nitrogen loading exceeded the criteria in almost all regions, and the phosphorus loading exceeded the criteria in more than 40% of the region.The NPS pollution was more serious in east than that in west of the lake.The Guangfu River watershed was the major contributor to the NPS pollution in Lake Nansi watershed.(3) The soluble nitrogen,flowed into the lake through streams,is the main form of loading in Lake Nansi watershed.While,the P loading in Lake Nansi watershed was mainly in the form of adsorption,which ran into river with sediment.

Abstract:Lake sediment should be pretreated before particle size analysis.It is necessary to eliminate the error caused by flocculation phenomenon of fine grain of sediment samples at the same time of effectively removing organic matter and carbonate particles.Surface sediment sample from the Lake Sanjiao in Wuhan was used for X-ray powder diffraction (XRD) to identify its mineral composition and clay species and automatic laser granulometer for grain size analysis.The XRD result demonstrated that the main nonclay minerals in sample were quartz and feldspar;while the clay minerals were primarily illite,kaolinite,chlorite.Furthermore, the result of grain size analysis showed that the grain size of 94.5% of component in sample was less than 30 μm.These characteristics made the sample easy to form flocculation at the pretreatment process of grain size analysis.Based on the results above,for the sample which are composited primarily with illite,kaolinite,chlorite,a single factor optimization method including ultrasonic concussion,dispersing agent and acid washing was used to check the optimum condition for eliminating flocculation.Results indicate that the optical condition for eliminating flocculation are ultrasonic concussion time: 6-8 min,dispersing agent concentration: 20 g/L,with acid washing before particle size analysis.

Abstract:Measurements of physicochemical components in the mainstream and tributaries of the Wuhua River system and application of methods of mass-balance and Pearson correlation analysis were conducted to investigate the atmospheric CO₂ consumption caused by rocks chemical weathering processes in the subtropical humid mountainous and hill region.Results show that the average concentration (77.11 mg/L) of the total dissolved solids within the Wuhua River was close to that (65 mg/L) in the world rivers, dominated by ions of Ca²⁺,Na⁺ and HO₃^- and followed by dissolved Si;ions of Ca²⁺,Na⁺ and HO₃^- were characterized by the effect of runoff dilution.Chemical runoff in the Wuhua River was dominated by silicate mineral weathering,followed by carbonate mineral.Atmospheric and soil CO₂ were major erosive mediums during rocks chemical weathering in the basin,with acids precipitation as the secondary erosive mediums.Comparatively,the atmospheric CO₂ consumption flux (2.14×105 mol/(km²·a)) by the rock chemical weathering processes in the Wuhua River basin is lower than that of the world.This is in agreement with the distribution of extensively rocks composed of silicate minerals,sparsely rock containing carbonate minerals.

Abstract:In order to restore the aquatic vegetation and improve local water quality,reconstruction of two ecological types of aquatic plants were carried out in two large enclosures in the Kangshan Bay demonstration area of Lake Taihu.By annual investigation, results showed that floating-leaved aquatic plants such as Limnanthemun nymphoides and Trapa bicorni,and submerged plant such as Potamogeton macckianus grew better than other plants under controlled conditions.Their coverage was quite high during the growing season.Results also showed that,controlling wind-driven wave disturbance and improving water transparency were the prerequisite for aquatic vegetation restoration;there was no difference about N and P contents between submerged macrophyte and floating-leaved aquatic plants,but floating-leaved aquatic plants performed better than submerged macrophyte in removing water N and P content.Concerning the economic and environmental benefit,aquatic plants including L.nymphoides,T.bicorni and P.macckianus with powerful anti-wave ability could be selected as the pioneering species to rebuild the aquatic vegetation in the open area of Lake Taihu.This research provided theoretical basis for ecological restoration in the open littoral area of Lake Taihu.

Abstract:Daphnia exhibits diverse morphological,behavioral and life-history responses to the kairomones of predators.A 10-day simulated experiment was conducted on anti-predation reaction of Daphnia similis,a dominant species in Lake Taihu,to invertebrate predator Chaoborus larvae.The experiment had three treatments: the presence of Chaoborus larvae (CL),control without Chaoborus larvae or filtered water (CK) and no Chaoborus larvae but with the filtered water that had cultured Chaoborus larvae the day before (FL).The results showed that the average body length,average number of offspring and cumulative number of offspring of D.similis in the CL and FL treatments were significantly higher than those in the CK treatment,which suggested that the release of kairomones from Chaoborus larvae can alter the life history traits of D.similis.These alterations can reduce the predation risk of D.similis.Our results indicate that invertebrate predator can affect the cladoceran population through both direct predation and release of the kairomones in the field.

Abstract:Phthalic acid esters (PAEs) are a typical kind of endocrine disrupting compounds.The levels of PAEs in urban rivers and lakes have already exceeded the national standards and their pollution is getting more and more serious.Resorting to root bags, removal of dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) was studied by an indoor Potamogeton crispus L.microcosm simulating the mainstream of Haihe River.An unplanted microcosm was set as a contrast.The experiments lasted for 27 d.Results indicated that the contents of DBP and DEHP in Potamogeton crispus L.increased by 133% and 68% at the end of the experiments.Concentrations of DBP in water were lower than the quantification limit (8 μg/L),while the contents of DEHP in water of planted and unplanted microcosms gradually decreased from the original values 65 and 70 μg/L to the quantification limit on the third day.Difference in the contents of DBP between non-rhizosphere sediments and sediments in the unplanted microcosm was not significant,and their removal efficiencies were 32.2%-36.5% at the end of experiments,while it was 50.0% in the rhizosphere sediments.The difference in concentrations of DEHP between non-rhizosphere sediments and sediments in the unplanted microcosm was also insignificant and their removal efficiencies were 10.3%-11.4% at the end of experiments.The contents of DEHP in rhizosphere sediments declined rapidly after 27th day and the removal efficiency was 80.9% at the end of experiments.Microbial results further revealed that the amount of microbial biomass in rhizosphere sediments were significantly higher than those in both non-rhizosphere sediments and sediments in unplanted microcosm.In the later experiment period,changes in microbial community structure in rhizosphere sediments were remarkable,which is consistent with the removal of the two PAEs in the rhizosphere.This suggests that submerged plants Potamogeton crispus L.can effectively remove the phthalate esters from sediments through the rhizosphere effect.

Abstract:A laboratory experiment was conducted to study the influence of nutrients (nitrogen and phosphorus) on the component of Microcystis cells (polysaccharide,protein,and RNA).These biochemical parameters were analyzed during the logarithmic phase.Results showed that the concentrations of N and P had limited effect on the content of RNA,which was relatively constant in each cell (about 2.0 pg/cell).However,the cellular contents of protein and polysaccharide were significantly affected by the N concentrations.The protein content was notably increased with the increase of N concentration,and the total polysaccharide content remarkably decreased on the contrary.The influence of P concentration on the total polysaccharide content was similar to that of N concentration,however,it showed little effects on protein content (nearly 4.6 pg/cell).The increase of N concentration could also promote intracellular polysaccharide (IPS) transform to extracellular polysaccharide (EPS),and the soluble part of EPS increased.Besides,the RNA and protein were rapidly synthesized when cells were in high growth rate,which caused the polysaccharide synthesis was too slow to produce enough extracellular polysaccharide for colony formation.Thus,it was difficult to form colonies during the laboratory incubation.

Abstract:Taking cyanobacterica blooms water samples collected from 12 different sites in Meiliang Bay of Lake Taihu in August 20,2011 as a research object,the phycocyanin extraction method including freeze thawing cycle,ultrasonic wave extracting,cellmelting and acetone were compared based on absorption spectrum and phycocyanin concentration.Results showed that the absorption spectrum of phycocyanin extracted by these methods have significant peak at 620 nm.The peak height is quite different among these methods: the highest peak is observed in freeze thawing cycle while the lowest in ultrasonic wave extracting,indicating that the four methods can extract phycocyanin from water samples,and freeze thawing cycle method is superior to others;Some phycocyanin specturm obtained by freeze thawing cycle,ultrasonic wave extracting and cell-melting appeared the second peak near 670 nm,and differentiated with the specturm of phycocyanin standard sample;The variation coefficient of phycocyanin concentration in the freeze thawing cycle method and ultrasonic wave method are less than 0.6,showing that their result is more precise and stable;The phycocyanin concentration showed that extraction efficiency of freeze thawing cycle method is better than the others,and so is recommended as a common method for phycocyanin extraction from cyanobacterica blooms water samples in Lake Taihu.

Abstract:The uptakes and removal effects of ammonium nitrogen (NH₄⁺-N) by Vallisneria natans and Myriophyllum spicatum under light (50 μmol/(m²·s)) and dark regimes were investigated in a laboratory experiment,with external NH₄⁺-N concentrations at 0,0.01,0.1,1 and 10 mg/L.The results showed that the absorption rates of NH₄⁺-N by V.natans and M.spicatum increased with external NH₄⁺-N concentrations and peaked at 1 mg/L,and then decreased at 10 mg/L.The absorption rates of NH₄⁺-N by the same plant species in the light condition was not less than those in the dark condition.The absorption rate of NH₄⁺-N by M.spicatum was not less than that by V.natans in the same light regime.Under dark regimes,with external NH₄⁺-N concentrations at 1 mg/L,the absorption rates of NH₄⁺-N by M.spicatum was 2.42-fold higher than that of V.natans.Under light regimes,with external NH₄⁺-N concentrations at 1 and 10 mg/L,the absorption rates of NH₄⁺-N by M.spicatum was 2.47-fold and 1.79-fold higher than that of V.natans,respectively.Therefore,at a certain range of NH₄⁺-N concentrations that macrophytes can tolerate, M.spicatum should be considered as the pioneer species for the restoration of macrophytes in eutrophic lakes.

Abstract:Effects of temperature (15,20,25 and 30℃) and Scenedesmus obliquus density (1.0×10⁶,3.0×10⁶ and 5.0×10⁶ cells/ml) on life history parameters including life expectancy at hatching,generation time,gross reproductive rate,net reproductive rate,intrinsic rate of population increase and proportion of sexual offspring of Brachionus diversicornis were studied by means of individual culture.Results showed that temperature affected significantly life expectancy at hatching,generation time,gross reproductive rate,net reproductive rate and intrinsic rate of population increase,but did not affect proportion of sexual offspring.Food level affected markedly gross reproductive rate and net reproductive rate,but had no effect on life expectancy at hatching,generation time,intrinsic rate of population increase and proportion of sexual offspring.The interaction between food level and temperature did not significantly influence all the life table demographic parameters.Both the life expectancy at hatching and the generation time decreased with increasing temperature.The lowest and highest net reproductive rate was obtained at 15 and 30℃,respectively;while with no difference between 20 and 25℃.The gross reproductive rate was lower at 15℃ than those at 20,25 and 30℃, and no difference was observed among those at the latter three temperatures.Both the net reproductive rate and the gross reproductive rate were higher at 3.0×10⁶ cells/ml than those at 1.0×10⁶ and 5.0×10⁶ cells/ml of Scenedesmus obliquus,and those at the two latter food levels were similar.

Abstract:The mtDNA cyt b gene of yellow catfish from five lakes in the middle and lower reaches of the Yangtze River was amplified and sequenced.Result showed that the average contents of A+T were a little higher than that of G+C in the aligned sequences of 955 bp.54 variable sites were detected and 37 haplotypes were recovered.The haplotype diversity and nucleotide diversity were 0.945±0.018 and 0.00419±0.00043,respectively.The genetic distance between Lake Taihu population and Lake Gehu population displayed the highest,up to 0.00651,while that between Lake Poyang and Lake Chaohu was the lowest to 0.00375.The fixation indices (F_st) of analysis of molecular variance (AMOVA) among populations was 0.0684,illustrating no significant population structure.The phylogenetic tree of cyt b built with MEGA 4.1 showed that five populations were not clustered into clades based on genetic distance.There was extensive general flow between yellow catfish populations from five lakes in the middle and lower reaches of the Yangtze River.

Abstract:Based on a detailed discussion about the conception of urban drinking water system adaptation,the paper established an adaptive capacity assessment index system and model of drinking water system in areas around Lake Taihu from the aspects of adaptation factors in water sources,water supply system,water user system,sewage treatment system and social system.According to the model and the sub-index and integrated-index,the drinking water system adaptive capacity,including spatial differentiation, types and influencing factors of cities around Lake Taihu area in Jiangsu Province,was evaluated.The results showed that: regions with strong adaptivity accounted for 29.1% with all five sub-systems high value;regions with middle adaptivity accounted for 41.2% with two types-relatively equal and uneven;regions with poor adaptivity accounted for 29.7%,mainly due to the technical sub-system is in low values and other sub-systems are not high.Therefore it is necessary to increase the differentiation enhancement of the adaptive capacity of each sub-system.