Abstract:Ecosystem in shallow lakes is generally subjected to the effects of multiple stressors, including nutrient, hydrology and climate.It is important to identify the impacts of multi-stressors for understanding the mechanism of environmental change in the lakes.Based on sedimentary proxies (i.e., ²¹⁰Pb and ¹³⁷Cs dating, diatom, geochemical indicators and particle size) from Chaohu sediment core and documentary data (i.e., hydrology, climate, population and agriculture) in Chaohu basin, this study estimated quantitatively the effects of nutrient, hydrology and climate on diatom succession since 1950 using the redundancy analysis.Before 1978 diatom assemblages were dominated by Aulacoseira granulata, followed by an abrupt increase in eutrophic species (i.e.Cyclostephanos dubius).Since 2000 diatom assemblages were characterized by C.dubius, with increases in eutrophic species (e.g., Cyclostephanos tholiformis and Stephanodiscus parvus).Results showed that sedimentary total phosphorus, total nitrogen, annual mean temperature, annual mean wind speed and annual water level amplitude were five significant variables, explaining solely 6.5%, 4.7%, 4.5%, 4.7% and 3.0% of the variances in diatoms respectively.Therefore, nutrient input was the most impor-tant factor on diatom succession.Meanwhile, changes in climate and hydrological conditions also imposed an effect on diatom suc-cession in Lake Chaohu during the last 50 years.

Abstract:Dissolved inorganic carbon isotope(δ¹³C_DIC) is an important element to reveal the carbon cycle in lake system.Factors influencing the variation of the δ¹³C_DIC value play an important role in paleolimnological study.However, there were only few studies focusing on the spatial variation of δ¹³C_DIC from closed lakes in China.In this study, we showed the characteristics of the δ¹³C_DIC values in waters of 24 lakes on the Qiangtang Plateau(QTP) and analyzed the affected factors for their spatial variations.The δ¹³C_DIC values in the 24 lake water varied between -15.0‰ to 3.2‰, with an average value of -1.2‰.The δ¹³C_DIC values in the closed lakes show high isotopic characteristics, some even higher than the atmospheric isotopic equilibrium value.DIC concen-tration and δ¹³C_DIC value in the closed lakes were significantly higher than those in rivers, but there was no significant difference between overflowing lakes and rivers.Although lakes on QTP had high pH value and high alkalinity, the average partial pressure of dissolved CO₂ (pCO₂) in the 24 lakes was several times greater than that of the overlying atmosphere.Gas CO₂ exchange between lake water and atmosphere is an important factor influencing the δ¹³C_DIC value in closed lakes.Due to the high DIC residence time, the long time gas CO₂ exchange makes the δ¹³C_DIC value close to the atmospheric isotopic equilibrium value.For lake water with high pCO₂, degassing of dissolved CO₂ in the water makes the δ¹³C_DIC value close to or higher than the atmospheric isotopic equilibrium value.For lake water with low pCO₂, invasion of atmospheric CO₂ makes the δ¹³C_DIC value close to the atmospheric isotopic equilibrium value.

Abstract:Carbon isotopes(δ¹³C) of carbonate from sediment core has been measured in Lake Caohai, Guizhou Province, south-west China.The results showed that δ¹³C values varied between -14.25‰ and 23.10‰, which was the largest amplitude of car-bon isotope variations and the highest positive values discovered so far in lacusrine carbonate sediments.On the basis of combina-tion with oxygen isotope, organic matter and carbonate content proxies, we suggested that the carbon isotope of carbonate from Lake Caohai was controlled by photosynthesis/respiration of aquatic plants, and the input of bacteria to carbon isotope fractionation of or-ganic matter might be responsible for the abnormal positive δ¹³C values in Lake Caohai.Therefore, much attention should be paid to the carbonate δ¹³C in Lake Caohai in the future research.

Abstract:Aimed at characterizing the assemblage structure of macrozoobenthos, identifying the key influencing environmental fac-tors and evaluating the water quality in terms of biological indexes, we investigated macrozoobenthos at 73 sites of the five river sys-tems (Rivers Tiaoxi, Nanhe, Taoge, Huangpu and Yanjiang)within Taihu Basin during April and June of 2010.Total 88 species from 48 families, 8 classes and 3 phyla have been found in the investigations.The mean density of macrozoobenthos was 5888.91 ind./m², in which the proportion of oligochaetes was 94.19%.The mean biomass of macrozoobenthos was 105.18 g/m², of gas-tropods with 72.50% in total biomass.Limnodrilus hoffmeisteri was the dominant species in all river systems.One-way analysis of similarity(ANOSIM)showed that macrozoobenthos assemblages in the Yanjinag River system differed significantly from other four river systems, and those of Tiaoxi and the Taoge River systems differed significantly.L.hoffmeisteri was primarily responsible for dissimilarities of macrozoobenthos assemblages among the five river systems, followed by Bellamya aeruginosa, Branchiura sowerbyi, Chironomus plumosus, Gammarus sp., Propsilocerus akamusi, Corbicula fluminea, Microchironomus sp., Chironominae sp., Glyptotendipes lobiferus, Tanypus chinensis and Alocinma longicornis.Canonical Correspondence Analysis showed that COD_Mn, PO₄-P, TN and NO₃-N were strongly correlated with the macrozoobenthos assemblages.The results of bioassessment using the BPI and the Wright Indexes indicated that the five river systems were mostly at status of intermediate polluted.

Abstract:Spatial distribution of arsenic (As) concentrations of sediments collected form ten medium-small scale lakes in Lake Dongting Plain was investigated, and the As pollution degree was evaluated using the geo-accumulation index.Average value of As sediment concentration from 10 lakes was 15.8 mg/kg, which varied from 10.1 to 33.7 mg/kg.It indicated that As sediment con-tamination was relative low.As to spatial distributions, the average contents of As in the superficial sediments were from high to low in the sequence of Yueyang South Lake, Bajiao Lake, Huanggai Lake, Anle Lake, Maoli Lake, Liuye Lake, Dong Lake, Shanpo Lake, Datong Lake, and Beimin Lake.As concentrations in the lake basins were from low to high in sequence of Lishui catchment (13.1 mg/kg), Ouchi catchment (13.4 mg/kg), Yuanshui catchment (16.2 mg/kg), and lakes at outlet areas of Dongting Lake (22.4 mg/kg).Degree of As pollution in lake sediments aggravated gradually from the upstream to the downstream of Lake Dongting drainage.Sediment sample analysis from 4 cores (Datong Lake, Huanggai Lake, Bajiao Lake and Shanpo Lake) showed that As had accumulated in sediments and increased from the bottom to the surface (30-0 cm).Geo-accumulation index a-nalysis showed that pollution level at 22 sites from eight lakes were none, and 7 sites from five lakes were at Level I.As a whole of Lake Dongting drainage, As pollution level in the superficial sediments was low.

Abstract:Polycyclic aromatic hydrocarbons(PAHs) of 16 types were measured in sediment from Xidayang Reservoir, Hebei Prov-ince, and the possible sources and potential risk assessment also had been analyzed.Total PAHs concentrations varied from 422.36 to 1052.90 ng/g in surface sediment, and increased continuously from reservoir upstream to the front areas of the reservoir dam.The total PAHs concentrations ranged from 388.81 to 1205.56 ng/g in a sediment profile, and increased continuously from the bot-tom(20 cm under the surface) to the surface sediment.Naphthalene, Phenanthrene, Fluoranthene, Benzo(b) fluoranthene, Chrysene and Pyrene were dominant compounds of PAHs in the sediment.The total PAHs concentration was positively correlated to TOC contents with a correlation coefficient of 0.91 in surface sediment and 0.93 in profile sediment.TOC absorbs more strongly high molecular weight PAHs(HPAHs) than low molecular weight PAHs(LPAHs).The main source of PAHs was originated from com-bustions of fossil fuels and biomass.In general, PAHs pollution in sediment appeared to be moderate to low leveling in Xidayang Reser-voir.Risk assessment suggested that PAHs was no significant biological impairment, suggesting a low toxicological risk up to now.

Abstract:An in situ simulation study about river purification was carried out in Taige Canal from November 2009 to July 2010, using artificial floating beds which were planted by plants Canna generalis, Oenanthe clecumbens and Lolium perenne.The research showed that the artificial floating bed can purify the river water uninterruptedly.The removal rates are 5% 35%, 5% 40% and 5% 20% for TN, TP and COD_Mn, respectively.The removal effects were better under the conditions of high temperature and the rapid growth of floating plants.Water exchange time in different seasons influenced the removal rates differently.Trend of removal loading with different temperatures and growing stages was similar to removal rates.However, the removal loading would increase with decrease of the water exchange time in any seasons.The main purification effects of artificial floating bed can remove the sus-pended solid and increase the Secchi depth, so that the particulate nutrient can be removed.In summer, it can removed dissolved phosphorus and ammonia nitrogen significantly.The floating bed had only few effects on the nitrate and nitrite nitrogen.Effects of artificial floating bed on the cycles of nutrients by the changes of physical and chemical environment deserve to pay more attentions.

Abstract:Taking Lake Taihu which was the third largest shallow lake in China as an example, we researched the demarcation of buffer zone on the basis of information collection, topographic survey and field investigation.On domestic and international litera-tures about buffer zones of lakes, we preliminarily defined approximately 2 km wide as the width of Lake Taihu buffer zone.Con-sidering the principles of land markers (villages, roads, mountains)and regional differences of regulations and planning, we de-fined the upper and lower boundaries of the buffer zone.The lower boundary was at the lake shoreline or levees around the lake.The upper boundary was at approximately 2 km from the lower boundary.According to land use types, there were three typical types of villages, roads and mountains in Lake Taihu buffer zone.The upper boundary at village area was divided by the adminis-trative villages about 2.0 km from the lakeshore, and was divided by roads when the roads are paralleled with the lake shores.At mountain area, the upper boundary was divided by mountain ridges.On the 1∶ 5000 topographic maps, we calculated 382.75 km in total length and 452.31 km² in the total area of Lake Taihu buffer zone by means of Auto CAD software.

Abstract:The healthy status of aquatic ecosystem in Lake Hongze is intermediate, but its ecosystem showed a trend of degradation year by year.It is necessary to build a scheme for healthy aquatic ecosystem of Lake Hongze before it will degrade further.The present study estimated the health status of aquatic ecosystem and investigated the characteristics and main problems.Three typical sub-areas, namely, water channel (from Huaihe Estuay of Lake Hongze to river-discharging channel), wetland protection area and Chengzi Lake were classified according to their properties of water quality, vegetation and hydrogeology.Following a general idea of "biotope restoration-aquatic plants recovery-aquatic system adjustment", a feasible scheme of building a healthy aquatic ecosystem for the different sub-areas was developed.The content included hydrological adjusting and ecological restoration of water channel, recovery and conservation of wetland, ecosystem recovery and algal bloom control in Chengzi Lake, improving and adjusting the ecosystem in Lake Hongze.

Abstract:The effects of Limnodrilus hoffmeisteri bioturbation on nitrogen releasing from sediments of the East Lake Dongting, with the different densities and environments were studied in this paper.The results showed that bioturbation of L.hoffmeisteri had a good accelerating effect on nitrogen release from sediments, which was caused mainly by ammonium release.When the density of L.hoffmeisteri was at 1 and 2 ind./cm², the concentrations of total nitrogen in overlying water were increased by 15% and 32% respectively comparing to the control test.Appropriate increasing of temperature was helpful for vital movement of L.hoffmeisteri, which caused that total nitrogen release increment were increased by 23% and 69% respectively when temperatures were 15 ℃ and 25 ℃ compared to the cotrolling 5 ℃.Adversity stress on L.hoffmeisteri, induced by acidic and alkali environments, enhanced its bioturbation effect and also accelerated nitrogen releasing.In comparison with a condition of pH 7, total nitrogen release increment were increased by 32% and 41% when pH values were 5 and 9, respectively.Total nitrogen release increment in hypoxia was 1.52 fold compared to the aerobic environment, which indicated that L.hoffmeisteri had good adaptability and survivability to hy-poxia environment in which bioturbation was stronger than in aerobic environment.

Abstract:The vascular flora in Lake Erhai wetland was investigated from May to December in 2009, and we found 145 species be-longed to 108 genera in 47 families, including 15 trees and shrubs, 75 hygrophytes, 15 emergent macrophytes, 26 submerged mac-rophytes, 7 floating-leaved and floating plants, respectively.The wetland held 15 communities, such as Salix cavaleriei, Zizania latifolia, Trapa natans and Potamogeton maackianus comm.Aquatic vegetation covered about 8% of total water area of the lake, and the average species number and biomass were 9 and 12.5 kg(FW)/m² in exploring sites, respectively.Richness index of Margalef species was 1.8706 in submerged macrophyte zone.Analysis with combinations of existing data indicated that plant diver-sity increased after enhancing management and lakeshore wetland restoration in the recent ten years and improved the situation of plant diversity decreasing in the northern lake.However, many problems still exist in the lakeshore wetland, such as narrow lake-shore areas, monotonous emergent macrophyte in the community, low coverage of aquatic vegetation, and the inherent flora ingredi-ent to be restored.In order to improve functions of the lakeshore wetland, to increase water transparency and to advance the cover-age of aquatic vegetation, we strongly suggest constructing the buffer areas.

Abstract:The phytoplankton biomass and concentrations of N and P in Lake Dianshan were investigated from January to Decem-ber, 2009, and relationship between phytoplankton distribution and nutritional factors was correlated by Canonical Correspondence Analysis.The results showed that there were two biomass peaks of phytoplankton within a year in Lake Dianshan.The one peak was in spring (March and April), and the other in autumn (August).The biomass of phytoplankton in spring(39.68 mg/m³)was higher than that in autumn (29.86 mg/m³).There were significant relationships between the nutrient concentrations and algae bi-omass in different seasons.The growth of phytoplankton was limited by phosphorus when the bacillariophyta and chlorophyta were dominant in Lake Dianshan from November to January.However, the growth of phytoplankton was limited by ammonium when the cyanophyta and chlorophyta were dominant in the lake from May to August.The higher nitrogen and phosphorus concentrations can-not significantly accelerate the growth of phytoplankton during the two outbreak periods of February-March and September-October, because there were interacted effects between nitrate and phosphorus.

Abstract:Sediment-Water-V.natans in a simulated lake system was built to study phosphorus concentrations in sediment, water and V.natans during the growth period of Vallisneria natans.Simulation results indicated that different phosphorus concentrations in sediment were reduced significantly during the growth period of V.natans.Total phosphorus (TP), NaOH extracted phosphorus (NaOH-P), HCl extracted phosphorus (HCl-P), inorganic phosphorus (IP) and organic phosphorus (OP) were decreased by 65.71, 39.06, 11.65, 52.86 and 11.28 mg/kg, respectively.The IP absorption efficiency of V.natans was higher than that of OP, and the NaOH-P absorption efficiency was higher than that of HCl-P.The concentration of TP in water was decreased to 0.04 mg/L.Redox potential (Eh) was increased significantly but pH was decreased in sediment.There were significantly positive correlations among TP, NaOH-P, HCl-P, IP and OP.Different phosphorus fractions were negatively correlated with Eh at different levels, significantly positive-correlated with pH, and significantly negative-correlated with V.natans root area.Phosphorus ab-sorbed by V.natans was 292.24 mg at the end of the experiment.The phosphorus in sediment, V.natans and water were 92.04%, 7.85% and 0.12%, respectively.The result indicated that V.natans affected the concentrations of phosphorus in sediment through increasing redox potential and decreasing pH.V.natans reduced phosphorus release risk through uptaking phosphorus from water and sediment.The rank from high to low order of phosphorus absorption ratio by V.natans was NaOH-P, HCl-P, IP, and OP.

Abstract:Culture solutions of the submerged freshwater macrophyte Vallisneria spiralis, incubated at 10 g(FW)/L for three days, were extracted by solid phase extraction(SPE)with broad spectrum cartridges, and eluted with different solvents.The acquired fractions exerted various inhibitory effects on the growth of Microcystis aeruginosa, and the methanol-eluted fraction showed the strongest effect.After removing the phenolic compounds from the fraction, the inhibition rate was decreased by 22.8%, indicating that the phenolic compounds controlled the algal growth inhibition of V.spiralis.Moreover, the methanol-eluted fraction was further separated by liquid extraction(LLE), and the acquired ethyl acetate fraction was analyzed by gas chromatograph-mass spectrometry (GC-MS).Nine phenolic compounds were identified:benzoic acid, p-hydroxybenzoic acid, p-hydroxyphenylacetic acid, phthalic acid, 3-(4-hydroxyphenyl)propionic acid, vanillic acid, protocatechuic acid, ferulic acid and caffeic acid.The algal inhibition test showed that the antialgal effects of the phenolic compounds were influenced by their structures.The multiple phenolic com-pounds, mixed at a ratio corresponding to their single toxicity, showed additive effects in most cases, which became much obvious with the increase of phenolic classes in the mixture.These results indicate that V.spiralis could release phenolic compounds to in-hibit the growth of M.aeruginosa, and the joint action of multiple allelochemicals may be an important allelopathic factor of sub-merged macrophytes to inhibit the growth of noxious cyanobacteria in natural aquatic ecosystems.

Abstract:Based on monitoring data of air temperature, water temperature and Chlorophyll-a(Chl.a)in Lake Chaohu from March to June in 2007, the relationship between air temperature, water temperature and Chl.a concentration were analyzed using statisti-cal methods.The results showed that:The daily determination coefficient of determination of quadratic polynomial fit between Ta and Tw was the highest(0.81).The hourly coefficients of determination between Tw and Chl.a concentrations varied in a wide range(0 0.91), and their mean value was 0.35.The correlation between daily Tw and Chl.a concentrations was higher than that of the hourly data.Furthermore, the correlation between Chl.a and cumulative water temperature of some single day was very high in the eastern part of Lake Chaohu while the correlation was low in western part of the Lake Chaohu.However, correlation between day-to-day Chl.a and water temperature was much better in the WCL than that in the ECL.

Abstract:Field work was carried out in Lake Kuncheng, Taihu Basin on April 23, 2010 to analyse the absorption characteristics of total particulates, phytoplankton pigment, tripton and chromophoric dissolved organic matter(CDOM).The results show:The ab-sorption coefficient of tripton is higher than that of phytoplankton pigment except for red wavelength at 675 nm.Absorption coeffi-cient of tripton spectrum becomes lower at the longer wavelength, and absorption of total particulates has the similar characteristics as that of tripton;Absorption coefficients of tripton and CDOM approximate exponential attenuation with increases of the wave-length, in which show certain relationships in different bands, and absorption coefficients of tripton at 400 nm and at 440 nm have good polynomial relationships with total particulate concentration;Relationships of the specific absorption coefficients between phy-toplankton pigment and chlorophyll-a concentration also can be well expressed by a polynomial function;Absorption coefficients from different sites of Lake Kuncheng sites show four different types of contributions to the total absorption coefficients.

Abstract:On the basis of observation for wind fields and wind wave fields in Lake Dianshan, the wind wave fields were numerical-ly simulated with the SWAN model.Comparisons of wave height between modeling and measurement indicated that the variation tendencies of the modeled wind wave fields were in agreement with those of the measured data.However, the fluctuation amplitudes of measured data are greater than those of modeled results.On the whole, the modeled wind wave fields are reasonable and relia-ble.Therefore, the wind wave fields in Lake Dianshan have been systematically simulated with different water levels and different wind fields.The modeled results can be taken as the reference basis for the flood prevention and environmental conservation of Lake Dianshan.

Abstract:The hyperspectral imager(HSI) is loaded on the HJ-1A satellite, which is a new source of home-made data with high spectral resolution and provides new remote sensing data for water quality, especially for lake water quality monitoring.Because the processing method of HSI images is underdeveloped, the quality evaluation and research for HSI images are necessary before it is extensively used in water-quality remote sensing.Suitability of lake water quality monitoring in Lake Chaohu by HSI image is as-sessed via data verifying, signal-to-noise computing, stripes removing and atmospheric correcting.The results show that HSI data of waterbody is reliable between wave bands 530-900 nm.Both 6S and FLAASH algorithm works well in atmospheric correction of HSI data, and the best range is at the 530-830 nm.

Abstract:Cultrichthys erythropterus is a common type of fish in Lake Taihu.Feeding habits of the fish were studied by analyzing 236 specimens from November 2004 to October 2005.The results showed that cladocerans and small fish were the dominant food items of C.erythropterus.Prey compositions of the fish varied in different fish body sizes.C.erythropterus longer than 130 mm in total length consumed more small fish, but that shorter than 130 mm-long mainly consumed cladocerans.In terms of feeding selec-tivity, C.erythropterus preferred Daphinia spp.and Limnoithona sinensis, but avoided copepodite, nauplius, Moina spp., Ceriodaphnia cornuta and rotifers.Thus the top-down effect of C.erythropterus varies with body sizes.The present paper also discussed the role of C.erythropterus in the ecosystem of Lake Taihu and made some suggestions for lake management and biomanipulation.

Abstract:Diaphanosoma is a dominant genus of cladocera in South China, and widely distributes in lakes and reservoirs.To un-derstand its regional population distribution, the animals were sampled in dry and flood seasons in 19 reservoirs of Guangdong Prov-ince during 2001 and 2006 monthly or seasonally in three reservoirs of Feilaixia, Xinfengjiang and Dajingshan, which have been under different trophic states.Adult Diaphanosoma was found in all reservoirs, where 5 reservoirs had only D.dubium, 8 reser-voirs had only D.orghidani, and 6 reservoirs had the two species.The two species showed an apparent difference in niches.D.dubium mainly dominated in eutrophic reservoirs, while D.orghidani did in oligotrophic reservoirs.Distributions of D.dubium and D.orghidani in the reservoirs can be well explained by their differences in morphology, food selection and ability of avoiding predators.

Abstract:The spatial and temporal distribution of rotifers, together with various environmental parameters, in Lake Buluntuohai were investigated from autumn of 2006 to summer of 2008, and the relationship between the distribution pattern of rotifers and the environmental parameters was analyzed accordingly.The results showed that 30 taxa were recorded in total and the dominant spe-cies included Polyarthra trigla, Filina longiseta, Hexarthra mira, Brachionus quadridentatus, Keratella quadrata and K.cochlearis.Both the rotifer density and biomass displayed a clear seasonal pattern with two peaks in autumn of 2006 and in summer of 2007.The spatial dynamics of rotifers during the two years were characterized by two distinctive features:The maximums of rotifer density and biomass were recorded in one of the bays in the lake, called Luotuobozi, and the biggest number of species was identi-fied in main water body, the open water in the lake.The density and biomass of rotifer were found to be in a decreasing order from sampling sites in the open water to eastern littoral zone and to western littoral zone.CCA results also showed that certain species, such as Polyarthra trigla were associated with water temperature, dissolved oxygen and the biomass of phytoplankton.The rotifer biomass in the lake was mainly determined by phytoplankton seasonally, while the biomass presents a negative relation with poten-tial predators(cyclopida)and competitors(cladocera)that both dominated the rotifer biomass.

Abstract:Genetic variations of three populations(Liangzi Lake population of 19, Longwo Lake population of 19 and Huaihe River population of 18) of Plagiognathops microlepis were studied by sequence analysis of mitochondrial cytochrome b(Cyt b) gene.Gene fragments of 1149 bp were acquired by PCR and DNA sequencing techniques.There were 10 haplotypes, 116 nucleotide variable sites and 10.09% of nucleotide polymorphic loci among three populations of Plagiognathops microlepis.As a base compo-sition, the content of A+T(about 57%) was obviously higher than that of C+G.Highest nucleotide diversity was observed in Huaihe River population(5 haplotypes, 111 nucleotide variable sites and 0.031223 of nucleotide diversity index), and lowest nucleotide diversity was detected in Longwo Lake population(3 haplotypes, 2 nucleotide variable sites and 0.000550 of nucleotide diversity index).Genetic distances between populations of Liangzi Lake and Longwo Lake, between populations of Huaihe River and Liangzi Lake, and between populations of Huaihe River and Longwo Lake were 0.001530, 0.084682 and 0.084335, respec-tively.There was a closer genetic relationship between populations of Liangzi Lake and Longwo Lake than that between populations of Huaihe River and the other two.Genetic difference between populations of Liangzi Lake and Longwo Lake has not risen to sub-species level, while genetic divergence between populations Huaihe River and Liangzi Lake and between populations Huaihe River and Longwo Lake may have arrived at subspecies level.