Abstract:Hydrodynamic conditions,including the flow velocity,discharge and water disturbances,play a key role in the occurrence, development,continuation and extinction of eutrophication.In order to prevent and control eutrophication,it is vital to study the influence of hydrodynamic conditions on eutrophication.Hydrodynamic conditions can not only affect the growth and interspecific competition of algae,but also change natural environment and nutrient loads of the water body.More details are as follows.(1) The flow velocity has a very significant effect on algae aggregation and distribution,as well as nutrients and the dominant algae.It is also found that there is an adaption period of the growth of algae biomass to the change of the flow velocity.(2) Discharge makes an effect on eutrophication mainly by altering the flow velocity and water quantity.(3) Water disturbance,which mainly originating from wind and tide et al,directly acts on algae cells and groups in strengthening the aggregation of algae,as well as influences the mixture and transportation of nutrients in vertical and horizontal directions.Reynolds Number and the type of water circulation are also regarded as hydrodynamic factors,which can make influence to eutrophication.At present,the study of hydrodynamic conditions' impacts on eutrophication is still in the stage of qualitative research.Some key issues,such as the influence on nutrients,the law of hysteretic nature and critical value of hydrodynamic conditions,still need further study.

Abstract:Altered hydrological connectivity between lakes and rivers may impose significant effect on lake ecosystems.Due to lacking of long-term data on lake environmental changes,the process and mechanism of limnological response to the changes in hydrological connectivity is still unknown.This work chose Lake Zhangdu from the Yangtze floodplain,to investigate the long-term (about 200 years) environmental changes responding to altered connectivity with Yangtze River using a high-resolution multi-proxy analyse on 210 Pb/¹³⁷Cs dating,diatom,geochemistry and grain size.Palaeolimnological records revealed that the lake has experienced three changes of the hydrological connectivity with Yangtze River,which matches well with the documentary records.Prior to 1954(stage I),the lake connected naturally with the Yangtze River and a low-nutrient,relatively deep and disturbed lake condition was inferred based on the high abundance Cyclotella bodanica.After 1954,with a dam construction(stage II),water residence time of the lake became longer and hence decreased in clarity,which favors the growth of Aulacoseria granulata.Correspondingly, nutrient enriched gradually which indicated by the slightly increase of eutrophic diatoms,as well as significant higher concentration of TOC and sedimentary TP,TN.In recent 20 years,lake became more eutrophicated inferred from high percentages of eutrophic species C.meneghinena,A.alpigena,Nitzschia palea,Surirella minuta and geochemical records including TOC,sedimentary TP,TN.After 2005(stage III),the lake condition improved slightly,indicated by diatom assemblage change with the increase of benthic species,although the concentration of TOC and sedimentary TP,TN were still high.Consequently,reconnection with Yangtze River may be an effective manner to relief the stressed floodplain lakes.

Abstract:Based on the simulated experiment in laboratory,physicochemical characteristics of sediment in eastern Lake Dianshan were measured,and release rates of ammonia,orthophosphate and dissolved organic carbon were measured under different simulated dredging depths and temperatures.The results were shown as follow: total phosphate and organic matter in surface layer of sediment increased several times during recent years in the eastern Lake Dianshan.The release flux direction of ammonia and dissolved organic carbon were from sediment to water column in the whole year,comparing to the reverse release flux direction of orthophosphate, except in summer.The role of sediment in phosphate cycle changed between "pool" and "source" in different seasons.The best dredging depth was 10 20 cm in the research area,and the best dredging season was autumn.The results provide information for the decision of dredging parameters in the practice of dredging project.

Abstract:Dissolved oxygen is one of the important parameters which describe whether the aquatic ecosystem is healthy or not.This research used meteorological data including wind velocity,direction and short wave radiation from August 16th to 20th in 2008 and relevant parameters for water quality module as an initial field to drive FVCOM(An Unstructured Grid,Finite-Volume Coastal Ocean Model),and simulated 3-D water temperature and dissolved oxygen of Lake Taihu.It turned out that the simulated results were fitted with the observed ones on the whole.The regression equation for water temperature is y=1.02x with the determination coefficient R²=0.690,comparing to R²=0.760 for dissolved oxygen.By analyzing the temporal and spatial distribution of dissolved oxygen,we preliminarily explored the influence of sources and sinks on the dissolved oxygen of Meiliang Bay.Solar radiation and wind speed were two important factors influencing the diurnal stratification of water temperature.Dissolved oxygen in Meiliang Bay in summer was influenced by water temperature and light with vertical distribution and presented "double peaks and double valleys" trend.Photosynthesis of phytoplankton was the most important source of the dissolved oxygen and light attenuation underwater directly controlled the vertical distribution of primary productivity.The respiration and death of phytoplankton depleted the most of dissolved oxygen,and the remaining dissolved oxygen was depleted by sediment oxygen demand,biochemical oxygen demand, bacterial respiration and nitrification oxygen demand,respectively.

Abstract:The paper studied the organic matter contents,humus composition and the degree of humification of the surface sediment of Lake Wuliangsuhai by chemical method.Correlation between sediment humus and physical-chemical factors were also discussed.The results showed that the organic matter of the surface sediment varied from 1.06% to 5.38%.Their distribution characteristics were related to hydraulic condition,aquatic plant distribution and human activities.In the humus composition,the content of humic acid and fulvic acid varied from 0.65 to 2.78 g/kg and from 2.19 to 8.72 g/kg,respectively.The humin is the main component in the sediment,ranging from 3.28 to 20.92 g/kg.Based on the correlation analysis of humus and environmental factors, each component is significantly correlated with the organic matter content.The pH value is significantly negative correlated with humin.Dissolved oxygen is significantly positive correlated with fulvic acids and significantly positive correlated with humin.The organic matter content increased while the content of extracted humic substances is decreased in the humification analysis.The PQ values range from 9.50% to 27.06%,with the average of 21.47%,which varied dramatically and with low degree of humification.

Abstract:Absorption coefficient has important scientific significance,acting as not only an important part of the inherent optical properties of waters,but also as the physical basis to build a bio-optical model.In this paper,dominant types of waters' absorption coefficient were classified and analyzed with the method of "Remote Sensing of Ocean Colour in Coastal,and Other Optically-Complex, Waters (IOCCG) "based on the in situ measurements during the period of 2008 2011 of three freshwater lakes (Lake Poyang, Lake Taihu and Lake Chaohu) in the middle-lower reaches of the Yangtze River.Because of the spectrals of a_d (non-pigment particles absorption),a_ph (phytoplankton pigment absorption),a_g (colored dissolved organic matter absorption) are greatly different, we consolidated the dominant types of IOCCG as type a_d-g and type a_ph-related.Results show that: 1) In autumn,the dominant type of Lake Poyang,Lake Taihu and Lake Chaohu is a_d,a_d-a_g,a_d-a_ph-a_g,respectively;In summer,Lake Poyang and Lake Taihu are co-lea_ded by two dominant types,they are a_d,a_d-a_g and a_d-a_ph-a_g,a_d-a_ph.2) Both dominant-type in summer, autumn of Lake Poyang and in autumn of Lake Taihu are a_d-g;however,Lake Taihu in summer and Lake Chaohu in autumn have the a_ph-related dominant-type.3) For the Gons and Gitelson algorithms and their assumptions,the applicability conditions are found inconsistency in different lake water and different dominant types.

Abstract:Phytoplankton absorption and chlorophyll-specific absorption coefficients were analyzed,and the causes were discussed by selecting four different trophic level lakes including Lake Taihu,Lake Tianmu and Lake Bositeng.According to trophic level index using chlorophyll-a(Chl.a),total nitrogen,total phosphorus and secchi disc,Lake Taihu includes hyper and medium eutrophication zones.Meanwhile,Lake Tianmu and Lake Bositeng are light eutrophic and mesotrophic,respectively.Phytoplankton absorption coefficients at 440 nm (a_ph (440)) are 1.02±0.51 and 0.69±0.40 for hyper and medium eutrophication in Lake Taihu,0.78±0.24 in Lake Tianmu,and 0.20±0.04 m^-1 in Lake Bositeng,respectively.Correspondingly,a_ph (675) are 0.59±0.32,0.38±0.23,0.41±0.13 and 0.08±0.02 m^-1,respectively.Statistics test shows that phytoplankton absorption of hyper and medium eutrophic Lake Taihu,in addition to light eutrophication Lake Tianmu,is significantly higher than that in mesotrophic Lake Bositeng.Chlorophyll-specific absorption coefficients at 440 nm (a_ph^* (440)) are 0.013±0.006,0.012±0.004, 0.038±0.008 and 0.051±0.013 m²/mgChl.a,respectively.Statistics test shows that a_ph^* (440) of Lake Taihu is much lower than that of Lake Tianmu,and a_ph^* (440) of Lake Tianmu is significantly less than that of Lake Bositeng.The order of the spectral absorption coefficient is as follows: Lake Taihu TⅠ > Lake Tianmu > Lake Taihu TⅡ > Lake Bositeng,showing that phytoplankton absorption coefficients generally increase with trophic levels,but Lake Taihu TⅡ is lower than Lake Tianmu partly due to the high concentration of non-algae suspended matter.In contrast,chlorophyll-specific absorption coefficients decrease with enhanced trophic levels.Phytoplankton absorption coefficients generally increase with trophic levels due to the increase of biomass caused by high nutrient concentration.However,the decrease of chlorophyll-specific absorption coefficients with enhanced trophic level may be attributed to pigment package.

Abstract:Using remote sensing images in the Badain Jaran Desert in 1973,1990,2000,2010,we got lake area change information and statistics on the desert lakes in different phases,then analyzed the spatial characteristics of lake area changes.Results indicated that there were some new lakes and area increase in some lakes,although the number and the area of lakes were reduced in each period.There are 19 lakes dry-up,7 lakes new,43 lakes shrunk,6 lakes expanded and 26 lakes stabled during 1973-2010.Spatially,the lakes with reduced area were distributed throughout the study area,while the lakes with increased area were mostly located in the east of the study area and in periphery of the middle-eastern region.The lakes with small changes in area were gathered.The lake area changes did not show a significant positive correlation in the entire space.The spatial characteristics of the lake area changes are probably due to different source supplies in different regions or the way of supply varies among the lakes.

Abstract:In search for the origin of groundwater,a detailed investigation of the stable isotopes of oxygen and hydrogen in the lake water,springs,well water,dam water,as well as soil water extracted from the four soil profiles in the Lake Daihai region,were carried out.Isotopic and hydro-chemical analysis found that apart from the direct precipitation supply,Lake Daihai is also recharged by the spring water.The mean isotopic compositions of local precipitation are much higher than those of spring water and well water collected from the surrounding areas,which means that the spring water is not supplied by the local precipitation.According to the isotopic analysis of soil water extracted from the four soil profiles around Lake Daihai region,the δD,δ¹⁸O values are significantly lower than those of the local precipitation.Furthermore,the TDS reach their peak values about 1 m beneath the earth surface,higher than the theoretical values due to evaporation.It evidenced that the local precipitation can not infiltrate into underground, in another word,the spring water of Lake Daihai is not supplemented by the local precipitation.In concluding,the results show that the main recharge source of groundwater in the Lake Daihai region is not local precipitation,but most come from a region where the precipitation is characterized by much lower δD,δ¹⁸O values.We can deduce that there is a kind of recharge ways we had not reveal before deep down in the earth's crust.In the Inner Mongolia plateau,deep-circulation groundwater from external drainage area is an essential source of recharge.

Abstract:In order to un derstand the dynamics and composition of metazooplankton community structure at the estuary of Maixi River in Lake Baihua,metazooplankton was investigated from August 2009 to August 2011.The results showed that there were 29 rotifer species with abundance ranging from 0.16 to 837.80 ind./L.Only two kinds of copepoda,Mesocyclops thermocyclopoides and Harpacticella sp.were detected,the abundance range from 0 to 642.75 ind./L.9 cladocera species were detected with abundances from 0 to 31.20 ind./L.Metazoan zooplankton abundance was mainly composed by rotifer and copepods.The proportion of rotifer abundance was from 4.09% to 100%,comparing to the percentage of copepods being from 0 to 95.64%.Asplanchna priodonta, Asplanchna brightwelli,Brachionus diversicornis were the dominant species for rotifer,whose highest abundance reached 424.88,392.20 and 61.99 ind./L,respectively;Bosmina longirostris as the dominant specie of cladocera,with a maximum abundance of 27.93 ind./L.Rotifer abundance was significant positive related to transparency,total nitrogen,nitrate nitrogen;while cladocera abundance exhibited a significant positive correlation with transparency and nitrate nitrogen,but significant negative correlation with the temperature.

Abstract:To broaden the stoichiometric characteristics of submerged macrophytes in plateau lakes and to restore them in eutrophic plateau lakes,10 lakes of Yunnan plateau were investigated in August 2010.Results showed that the number of species declined with the increase of eutrophic level and most of them belonged to Potamogeton and Myriophyllum.The tissue contents of total carbon(C),total nitrogen(N) and total phosphorous(P) in these 10 lakes ranged from 170.22 373.14 mg/g,0.90 9.70 mg/g and 0.36 4.30 mg/g,respectively.The ratios of C:N,C: P and N: P in 10 lakes ranged from 37.21 188.47,83.18 468.02, 1.57 4.90,respectively.Results of Spearman rank correlation analysis indicated that no significant correlations were found between N: P and environmental factor,such as limnological and physicochemical parameters.As for individual species,the highest mean values of C,N,P,C:N,C: P and N: P were 368.41 mg/g(Potamogeton malaianus),7.60 mg/g(Potamogeton lucens), 3.26 mg/g(Potamogeton pectinatus),68.93(Potamogeton maackianus),224.57(P.lucens),4.82(P.lucens),respectively.We concluded that P is excess and N is relatively limited in these 10 selected lakes,and P.pectinatus,P.maackianus and P.lucens may be the more suitable species for the restoration of eutrophic plateau lakes.

Abstract:Roots of Nymphoides peltata collected from Lake Taihu were cultured under three different temperatures (28,30, 32℃).The biomass under such different temperature conditions were 0.0019±0.0002,0.0021±0.0003 and 0.0020±0.0003 g (DW)/cm²,respectively.Meanwhile,the dry weight of stem and root was maximum under 30℃ than other treatments that had significant difference;the order of the dry weight and biomass per unit area of leave was 30℃ > 28℃ > 32℃.Light response curves and ACI curves were determined by a Li-6400 portable photosynthesis analysis system,and the non-rectangular hyperbolic method was used to fit the curve to obtain relevant photosynthetic parameters.The results showed that the influences of temperature on order of N.peltata photosynthetic capacity was 30℃ > 32℃ > 28℃,the order of carboxylation efficiency was 32℃ > 30℃ > 28℃,transpiration efficiency and stomatal conductance showed the same trend,30℃ > 28℃ > 32℃.The photosynthetic capacity of N.peltata increased significantly with the increasing temperature,and the growth of N.peltata was promoted;however,the photosynthetic efficiency reduced when the temperature exceeded 30℃ with the suppression of N.peltata.In the appropriate temperature range(< 30℃),small amplitude warming(2℃) produced a significant effect of accumulated temperature(200℃·d), which promote the growth of N.peltata.It is deduced that the phenomenon that the average temperature of Lake Taihu increased about 1℃ during 1998 2006 may promote the expansion of N.peltata in Lake Taihu in recent years.

Abstract:Taking aseptic seedlings of P.crispus as the experimental material,the effect of different concentrations of Cu²⁺ (0,1, 2,4,8,12 μmol/L) on the metabolism of polyamine(PAs) and reactive oxygen were investigated.With the increasing of Cu²⁺ concentration,the results indicated that: (1) Superoxide dismutase(SOD) activity increased markedly,while the activities of peroxidase(POD) and catalase(CAT) increased progressively followed by a decline.(2) The generation rate of O₂^-· and the content of H₂O₂ and MDA increased,while soluble protein content decreased.(3) Free putrescine(Put) content first enhanced and then reduced notably.However,the content of free spermidine(Spd) decreased gradually and spermine(Spm) increased significantly.Therefore,the ratio of free (Spd+ Spm)/Put promptly increased under high concentrations of Cu²⁺ stress.The changes of total PAs content were similar to those on free PAs.Perchloric acid soluble conjugated(PS-conjugated) Put and Spm changed in the same pattern as free PAs.While PS-conjugated Spd content increased slightly.In addition,the content of perchloric acid insoluble bound(PIS-bound) Put and Spd first increased and then decreased,but they were still higher than those in the control.Moreover, PIS-bound Spm content declined.(4) With the increase of Cu²⁺ concentration,the activity of arginine decarboxylase (ADC) sharply decreased after a transient increase,while the activity of ornithine decarboxylase(ODC) did not change significantly.Polyamine oxidase(PAO) and diamine oxidase(DAO) activities increased gradually,followed by a decrease.Our results suggested that Cu²⁺ stress induced obvious oxidative damage on aseptic seedlings of P.crispus.The up-regulation of antioxidant enzymes activities and Spm content,the changes of Put into Spd and Spm as well as the conversion between different forms of polyamines played a key role in the adaptation mechanism of aseptic seedlings of P.crispus under Cu²⁺ stress.

Abstract:Obvious dolomite deposition during the Holocene was found by using X-ray diffraction analysis in Lake Huahai,Hexi Corridor.The dolomite deposition was in deoxidizing environment during the Holocene according to the lithology,sediments characteristics, gypsum and the changes of Fe³⁺.It provided new evidence for the research of dolomite formation.Dolomite,as a kind of carbonate mineral,can indicate the lake water salinity.However,it can not indicate the salinity increase directly.The decrease of dolomite content is corresponded with the increase of salinity in sulfate lake.Dolomite and gypsum changes in Lake Huahai can be used to reconstruct lake salinity during the Holocene.During 10.47 8.87 cal ka B.P.,lake salinity was high,implying the climate change from arid to humid.During 8.87 cal ka B.P.,a mount of gypsum deposition revealed increase in water salinity and arid climate.After that,water salinity decreased and the climate was humid.After 5.50 cal ka B.P.,hiatus indicated arid climate.

Abstract:Using multimodel ensemble mean results of 8 global coupled ocean-atmosphere models in the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) by bias-corrected statistical downscaling method,possible changes of surface air temperature and precipitation over Huaihe River basin were predicted in future (2011-2040) relative to baseline (1961-1990) under SRES A2,A1B and B1 scenarios.The results indicate that (1) multimodel ensembles can reproduce a large-scale spatial distribution of annual,seasonal temperature and precipitation over the Huaihe River basin.It can also reflect better on monthly temperature and precipitation distributed processes within the year.Compared with the observations,the monthly temperature has a difference about 0.2℃ (expect winter),and the precipitation has a difference about 5% (except September).(2) The annual and seasonal temperature presents an upward trend under different scenarios.The annual temperature increases with a range of 0.85 1.12℃,while temperature in winter and spring increases more obviously than that in summer and autumn.(3) The annual precipitation increases with a range of 0.13% 5.24% in future,but the changes are not significant.Seasonal precipitation presents an increasing or decreasing tendency,however seasonal,interannual and interdecadal precipitation changes are more complex.The spatial pattern of precipitation varies obviously under different scenarios.

Abstract:Astreamflow drought index was calculated by using monthly runoff from 1959 to 2009 at Makou hydrologic station in the lower reaches of the Xijiang River.The hydrologic drought duration and intensity was characterized through run theory,which were used to construct the bivariate joint distribution model in this paper.The results of drought duration and intensity joint distribution model show that: (1) There is high correlation coefficient of 0.617 between streamflow drought duration and intensity;(2) The marginal distributions of drought duration and intensity can be better represented by three-parameter Weibull distribution;(3) The Gumbel-Hougaard copula which belongs to Archimedean Copula family was selected for constructing the joint distribution model of hydrological drought duration and intensity by using goodness-of-fit test;(4) The 5 10 years return period and twenty years return period of hydrologic drought can reach to heavy drought level and extreme drought level,respectively;(5) The encounter probabilities can be provided for diagnosis and prediction of drought characteristics for the correspondence between specific drought duration and hydrological drought levels or between specific drought intensity and drought duration in the probability sense.

Abstract:The Huaihe River basin is located in the transitional zone from north subtropical to south warm temperate climate.The characteristics and influential factors of precipitation in different fields are various.This study investigated the distribution and determined the influential factors of precipitation in flood season over the Huaihe River basin.For this goal,the meteorological observation data of 145 stations from 1961 to 2010 were collected and analyzed.The percent of different intensity rainfall days and the ratio between storm days and rainfall days were calculated.Finally,the temporal variations of meteorological observation data were analyzed.The results showed that rainfalls in the southern of Huaihe River basin are higher than those in the northern,affected by several factors,such as terrain,moisture and wind.Meanwhile,rainfall exhibited temporal characteristics,with the percent of storm cases and ratio of storms to rainfall increasing from 1961.This study derived two main conclusions: first,the precipitation of the Huaihe River basin became heterogeneous in spatial and temporal distribution with the changing of climate;second,the heavy rain cases such as storm occurred more frequently than before.

Abstract:Coupling radar-rainfall data with distributed hydrological model was important in improving flood forecast precision and leading time.However,radar-rainfall error propagation in hydrological model largely affected runoff process simulation.In this study,the operational radar-rainfall data,provided by Huaihe River basin Meteorological Center,was analyzed.With HEC-HMS hydrological model input,radar-rainfall data was used to simulate and analyze the runoff process of rainfall concentration period,in the Xixian hydrological station of Huaihe River basin,during July 1 10,2007.The results showed that runoff simulation based on radar-rainfall data was consistent with the simulation based on rain gauge data.The radar-rainfall input error had been decreased obviously after the propagation of the HEC-HMS model.Runoff simulation based on radar-rainfall data by union calibration was the best,whose relative error were-20.2% and-13.3% for flow process and peak flow,respectively.

Abstract:Abstract: We carried out a six-year survey on fish resource of Cihaxia to Jishixia stretches in the upper reaches of Yellow River from 2005 to 2010.Totally,39 fish species were found and were belong to 6 orders,9 families and 29 genera.Among these,only 16 species were native and more than 20 exotic species widely distributed in the upper reaches of Yellow River.7 species including 1 native and 6 exotic species are new recorded for this stretch.Based on composition of catches,we evaluated the species diversity using Margalef richness index,Shannon-Wiener index,Simpson dominance index and Pielou evenness index,respectively.The results showed that the stretches from Cihaxia to Jishixia of the upper reaches of Yellow River holds low fish diversity,which can be attributed to the high altitude and deterioration of the environment.There are significant difference in catches composition among sample sites.We also investigated that fish feeding,spawning ground,and reproductive period and habitat characters of the dominant species.

Abstract:In this paper,we reported water depth,water quality and modern sedimentation rates of Mapam Yumco and La'ang Co, southern Tibet,based on field investigation conducted in 2009 and 2010,respectively.Bathymetric survey showed a rather regular shape of Mapam Yumco with a maximum depth of 72.6 m and flat in the middle part of the lake.In La'ang Co,there are shallow fluvial fans in the north part and open areas in the south,which are connected by a narrow channel.The deepest part of La'ang Co is 49.03 m which lies in southern basin.The water volumes of the two lakes are 1.462×10¹⁰ m³ and 5.711×10⁹ m³,respectively, according to the calculation based on water depth data.For the physicochemical profile feature of Mapam Yumco,a thermocline existed between 25-35 m with a temperature gradient of 0.17℃/m.Conductivity,pH and dissolved oxygen showed synchronous abrupt changes in the thermocline.In La'ang Co,temperature decreased abruptly between 5-15 m with a gradient of 0.16℃/m.Meanwhile,pH changed to weak acid condition from surface to bottom,while the dissolved oxygen changed oppositely which may caused by respiration of aquatic plants.In Mapam Yumco and La'ang Co,major ionic composition showed similar features except Ca²⁺,major ions in La'ang Co were approximately three times of Mapam Yumco in concentration,while Ca²⁺ was only half of Mapam Yumco.210 Pb and ¹³⁷Cs method was used to determine the modern sedimentation rates of both lakes,the results showed that it was 0.31 mm/a and 0.65 mm/a in Mapam Yumco and La'ang Co,respectively.

Abstract:A brief introduction of the book titled "An ecological insight on the design, operation and evolution of life system: integration of ecology, genetics and evolution through sexual reproduction" by XIE Ping(2013),Science Press