Abstract:In laboratory culture Microcystis aeruginosa occurs mainly as single cells but under natural conditions, it is normally in the colonial morph. This phenomenon suggests that some factors may be responsible for the occurrence of colonies in lakes. In the present experiment we investigated the grazing effect of flagellate Ochromonas sp. on physiological changes in M. aeruginosa using flow cytometry. The experiment was run in triplicate for 9 days at 25℃ in photoperiod of 12L:12D. Results showed that M. aeruginosa population exposed to flagellate grazing decreased sharply and some single cells formed colonies, most of which were made up of several or dozens of cells. Colony formation can deter flagellate from further grazing on a certain extent. Esterase activity and chlorophyll fluorescence of M. aeruginosa cells under flagellate grazing were significantly higher than those of unicells in the control, whereas the cell size of M. aeruginosa became smaller under intense flagellate grazing. The enhanced esterase activity may contribute to colony formation. The fact that cell size of M. aeruginosa under flagellate grazing became smaller may indicate that M. aeruginosa adopt a kind of ecological strategy to grow rapidly under intensive grazing.

Abstract:Data of 20 year monitoring of water quality, algal bioassay, and remote sensing information were analyzed to determine the long-term effect of nutrients (N and P) on algal growth. Since the first algal bloom in 1985 and the accumulation of nutrient, Lake Dianshan has become hyper-euthophicated. The concentrations of TN, TP and Chlorophyll have rapidly increased since 1999, and their annual rates were 2.25, 6.67 and 3.40 times respectively higher than that of the past 15 years, among which phosphorus was the highest. The transparency decreased 5cm annually. Algal community has been transited to green-bluegreen algae dominated since 1999, the frequency of algal bloom occurrence were 2-3 times of before. When concentration of TN in water column was higher than 3.5mg/L, AGP test did not have any positive response at any significant levels. In situ experiment in 2002 and regression analysis of frequencies between algal bloom and higher concentration of TN found that during the period of summer-autumn, algal growth could be increased when TN was around 3.5mg/L: the higher TN concentration, the more frequency algal bloom. The evidence showed that Lake Dianshan was of high risk of harmful bluegreen algal bloom.

Abstract:Peeper technique was used to sample the interstitial waters in the sediments of Fubao Bay in Lake Dianchi, and the vertical distributions of NH₄⁺-N and PO₄^3--P in the waters were analyzed. The activities of microbe (the activity of FDA) and alkaline phosphatase (APA) in the surface sediments were also studied. The results showed that concentrations of NH₄⁺-N and PO₄^3--P in the interstitial waters generally increased, then decreased, with the depth, reflecting a possible diffusion trend for these nutrients. The decreasing trend was observed for the contents of organic matter (Reflected by Loss-on-Ignition, LOI), the activity of FDA and the APA in the 10cm surface sediments. The order of concentrations of NH₄⁺-N and PO₄^3--P in the interstitial waters, as well as the LOI, the activity of FDA and the APA in the surface sediments, ranked as estuary> the center of the bay > the west coast of the bay > the east coast of the bay. Regression analyses showed that concentrations of NH₄⁺-N in the interstitial water were positively correlated with the activity of FDA and the APA in the surface sediments (0-10cm), while the concentrations of PO₄^3--P were negatively correlated with them and the coefficient was very low.

Abstract:The average contents of total phosphorus and active phosphorus concentration were 0.113mg/L and 0.011mg/L, respectively; the inorganic phosphorus-degrading bacteria and organic phosphorus-degrading bacteria in the sediment was 6.73×10⁵ cells/g dry sediment, but it was only 71cells/g in the water, and there was also significant temporal and spacial difference. According to the bacteria group's shape, 3 representative inorganic phosphorus-degrading bacteria and 7 dominant organic phosphorusdegrading bacteria were isolated. Identification showed that the 3 representative inorganic phosphorus-degrading bacteria were similar to Bacillus megaterium, Pseudomonas sp. and Paenibacillus sp. The 7 dominant organic phosphorus-degrading bacteria were similar to Bacillus thurigiensis, Bacillus pumilus, Bacillus sp., Bacterium sp., Microbacterium oxydans, Bacillus cereus and Bacillus simples. The phosphorus-degrading bacteria of Lake Taihu were classified into Bacillus and Pesudomonas. The contribution of inorganic phosphorus-degrading bacteria for the aquatic bioavailable phosphorus was greater than that of organic phosphorus-degrading bacteria.

Abstract:Five strains of Planktothrix agardhii isolated from five regions around China were studied for their physiological characteristics, including growth rate, pigment composition, photosynthetic activity. Strain HAB1128 isolated from Guangzhou contained lower chlorophyll-a(Chl.a), but higher C-PC content and higher C-PC ratio in total phycobiliprotein compared to other 4 strains. Results from electron transfer rate (ETR) showed that HAB1128 had higher photosynthetic ETR and the maximal ETRmax, which inferred that high-performance electron transfer chain retrieved the inadequacy of Chl.a of this strain, and lead to the neutral growth rate. On the contrary, HAB631 the strain isolated from East Lake (Wuhan), contained higher Chl.a content, but showed lower growth rate due to its weak electron transfer chain. No significant differences of physiological parameters were shown among three strains isolated from Beijing, Shanghai and Yunnan.

Abstract:In order to understand the HCO₃^- utilization in algal photosynthesis, net photosynthetic rate (NPS) under different pH values and photosynthetic bicarbonate uptake rate (PCU_BC) were investigated. The results indicated that the NPS of Scenedesmus quadricauda were all higher than that of Microcystis aeruginosa from weak acid to weak alkaline cultures. The PCU_BC, characterized as a parameter of bicarbonate utilization of alga and calculated as an average of photosynthetic carbonate uptake rate in pH range over pH turning point (pH_TP), were 142.14 and 314.08μmolDIC/(g·h,FW), respectively, for M. aeruginosa and S. quadricauda, which displayed higher ability to utilize bicarbonate in photosynthesis of S. quadricauda. Addition of 0.8mmol/L of AZ (acetazolamide) caused 100% inhibition of PCU_BC for M. aeruginosa; PCU_BC decreased to 0 when 1.6mmol/L of AZ presented for S. quadricauda. Presence of 1.2 mmol/L DIDS (4,4'-diisothio cyanatostilbene-2,2'-disulfonic acid) inhibited PCU_BC by up to 56.10% and 39.74% for M. aeruginosa and S. quadricauda, respectively. These inhibiting results showed that M. aeruginosa was more sensitive to inhibitors than S. quadricauda, and suggested that bicarbonate can be used by these two algae in photosynthesis and that both algae tested are stronger bicarbonate users.

Abstract:Low dissolved oxygen biofilm reactor was used to treat the mixed wastewater in a village in north bank of Lake Dianchi. The purpose of the operation was to remove the solid waste, which was difficult to settle down naturally, so forth tofacilitatethe next step of wetland purification. A field experiment was undertaken for 12 months in nature conditions. The result showed that when the hydraulic loading rates between 3 and 12m³/(m²·d), Air/Water ratio between 1:1 and 2:1, DO was controlled between 0.1 and 2.0mg/L, the reactor could remove the organic matter efficiently. When the loading rates of COD under 0.58kg/(m³·d), removal rates were above 60%. Low dissolved oxygen slowed the desquamation of biofilm and its thickness was reached to 800μm. Process of obstruction and adsorption was enhanced for SS removal and the average removal rate was 90.7%. The experiment found that there was still some removal effect of nitrogen and phosphorous in low dissolved oxygen in the reactor. Energy cost was significantly reduced by decreasing aeration. At the flux of 4000t/d, the calculated treatment expense was 0.05-0.1RMB/t. Although the concentration of COD and SS of mixed wastewater was greatly fluctuated, the outflow quality and biofilm growth was relatively stable. It's suitable for further stable disposal and the treatment of suburb low concentration mixed wastewater. It provided a new technical for wastewater control in suburb area of Dianchi basin.

Abstract:The integrated restoration project in Lake Lichee in Shenzhen, China, is taken as a case study to investigate the treatment effect of the different units in the restoration project based on 9 months', field monitoring data. The results showed that, the mean removal rates were 33.6% for TP and 16.2% for COD via a filtration unit; 39.0% for TP and 21.3% for COD via a bio-gravel-layer unit; and 80.2% for TP and 56.1% for COD via a man-made wetland unit. A total phosphorus modeling of each sub-lake for Lake Lichee was developed and applied to compute time needed to improve water quality to match Grade IV of surface water standard under the designed conditions. The result showed that it will take 2.5d subject to 24h operation of the restoration project per day to reduce TP concentration lower than 0.1mg/L in Lake Lichee. During the process, TP removal load is about 7.27kg, and the removal rate is almost 46.9% in Lake.

Abstract:Vertical distributions of nitrogen contents, net nitrification rates, net N-mineralization rates and nitrate reductase activities in sediments of Lake Yuehu in June, 2005, were described on basis of four samples from the lake. The results showed that there was a critical layer in which exchangeable nitrate contents were the highest. Exchangeable ammonium and available nitrogen contents were the lowest in the subsurface sediment (5-10cm). Available nitrogen was stored mainly in the form of exchangeable ammonium in both surface (0-5cm deep) and deeper layers (>10cm deep) where their contents were higher. The pattern of this distribution can be explained by anaerobic conditions. The surface sediment not only showed higher contents of total nitrogen and organic nitrogen, rates of net nitrification, N-mineralization and nitrate reductase activities, but also displayed the highest ammonium and the lowest nitrate concentrations in interstitial water. Therefore, based on a nitrogen cycling mode, we proposed that organic nitrogen was re-mineralized to ammonium and nitrate with processes of the former being nitrified into the later, resulting in anaerobic conditions that contributed to ammonium accumulation by the production of its own and nitrate reduction in interstitial water of surface sediment. In general, the surface sediment in eutrophic lakes, enriched by organic nitrogen, is the most active dimension for the biogeochemical cycling of nitrogen with ammonium being the major and most effective forms.

Abstract:Cladoceran microfossils can reflect the historical population dynamics and are an important indicator of paleoenvironments. The present study was aimed to analyze the historical variation of cladoceran assemblage and abundance, and its driving factors by examining cladoceran microfossil of the sediments in western Lake Taihu (near Mashan). A total of 14 cladoceran species belonging to 10 genera were identified. The most abundant species were planktonic Bosmina spp. with an average relative abundance of 95.4%; the second were Alona spp., with average abundance of 4.2%; Chydorus spp. and all the other species were less than 1%. The increasing tendency of nutrient levels of Lake Taihu was showed by the vertical changes of cladocera assemblage and abundance of the sediments. B. longirostris cornuta and A. rectangular, which prefer eutrophic conditions, showed an increasing tendency from bottom to upper layer, while A. intermedia, which commonly appearred in lower trophy, showed a decreasing tendency. The dramatic decrease of cladocera absolute abundance and the disappearance of A. intermedia at the surface 3cm sediments probably indicated the rapid nutrients loading since late the 1980s. In addition, the historically changes of water level/area and the increasing trophic states after the late the 1980s were represented by the ratio of plankontic to littoral species (P/L). Our results showed that natural conditions were the major factors which affected the population dynamics of cladocera before the 1960s, the human activities strengthened since the 1960s, and finally played the determinant role in the population dynamics of cladocera in Lake Taihu.

Abstract:700 sediment samples were collected from Lake Dongting during 2003-2004, and concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, Zn in the sediments were measuremed. The results showed that the average concentrations of Cd, Cr, Cu, Pb, Zn did not exceed the standards of Class II of environmental quality standard for soils in China; the average concentrations of As, Hg and Ni were between the standards of Class I and the standards of Class II of the standard. The heavy metals in east Lake Dongting and south Lake Dongting were mostly accumulated in the front of the delta where rivers ran into the lake, however the heavy metals in west Lake Dongting were mostly accumulated in the rear part of the delta. Results with integrative index of geoaccumulation showed that the decreasing order of the degree of heavy metal pollution in Lake Dongting was as follows: south Lake Dongting > east Lake Dongting > west Lake Dongting > Lake Datong > Chenglingji . Principal component analysis (PCA) was applied to study the heavy metals in the sediments from Lake Dongting. Results showed that the first principal component (PC1) in south Lake Dongting accounts for 55.22% of total data variance, and the second principal (PC2) accounts for 30.04%. As, Cd, Hg, Pb, and Zn have greater loadings in the PC1, and Cu, Cr and Ni have greater loadings in PC2, in south Lake Dongting and east Lake Dongting. For the west Lake Dongting, Lake Datong and Chenglingji, due to the fact that they have different sources of heavy metals, the principal component analyses have shown different results.

Abstract:Metal profiles of short sediment cores were drilled from Lake Shudu located in Xianggelila County, northwestern Yunnan Province. Core samples were dated by measuring anthropogenic ³Cs. Cluster analysis showed that metals in the core sediments were divided into two groups. The first group of metals (Al, Mg, Co, Zn, Cr, Ti, V, Cu, Ni) has similar concentration profiles to that of clay concentration. Metal concentrations are low at 25-10.25cm and increase towards the surface. The first group metal concentrations are mainly influenced by summer precipitation. The second group metal has different features: at the bottom of the core Pb concentration is low and increase upwards. Pb concentration at 17.5-10cm quickly increased and gradually reduced due to mining activities nearby the lake in the 1950s. High Pb concentration at 10-0cm can be interpreted as air pollution produced by coal and oil combustion after 1986. Concentrations of Fe and Mn at 25-7.5cm are likely caused by remobilization at the sediment-water interface after sedimentation. Fe and Mn concentration at 7.5-0cm significantly increased. Increasing precipitation between 1986 and 2005 resulted in strong erosion and soil gleying within the catchment which maybe the reason of high concentrations of Mn and Fe at the top of the core.

Abstract:Sediment samples collected at 126 sites in Lake Dianchi were analyzed to determine their metal concentrations of copper, zinc, lead, cadmium, chromium, mercury, and arsenic at different depths of the sediment cores (0-5cm, 5-10cm and 10-20cm). Based upon the consensus-based sediment quality guidelines (CBSQGs), the threshold effect concentration (TEC) and the probable effect concentration (PEC), five sedimentary environment quality grades were classified and assessed by employing the method of the grey clustering analysis. Results showed that sedimentary environment quality in Lake Dianchi is mostly in the third grade (III) with a moderate metal contamination. Sediments are the third grade (III) at the depths of 0-5cm and 5-10cm, and the second grade (II) at the depth of 10-20cm. Generally, sedimentary environment qualities in the deeper layers are better than in the upper layers, indicating that metal contamination in Lake Dianchi sediments trends towards worse.

Abstract:Based on the data of flood peak levels and flood disaster losses in Lake Poyang region during the period of 1950-2002, this paper established the correlation model between the annual flood peak levels and flood disaster losses, analysed the statistical pattern and regularity of flood disasters and flood disaster losses in Lake Poyang. A scheme of 6-grades was established for floods and areas of flooing in the Poyang region, which revealed that most of the floods occurred once every 2-5 year and are smaller than Grade 3 flood (once every ten year). Lake Poyang had 24 floods during 1950-2002, which accounts 1/3 of total flood disaster losses of this period. Although, Grade 4 floods (once every 5 year) were recorded only 7 times, they account 2/3 of total flood disaster losses. We believe, to low peak flood levels by comprehensive and integrated measures and management, and to increase the capacity of flood prevention for the dyked lakeside farmland are the effective options for mitigation of flood damages and losses.

Abstract:To examine the effects of land cover change on hydrologic process, the BTOPMC model is applied to simulate the daily runoff in the study area controlled by the Huangnizhuang Hydrologic Station in the period of 1982-1986 based on four land cover scenarios. The results show that the land cover change influences the calculation of evapotranspiration and runoff obviously. Compared with the current land cover scenario, the evapotranspiration of the forest scenario increased and the runoff of it decreased. The case was opposite for woody savannas and cropland scenarios. The variation of runoff in dry season was smaller than that in rainy season under various land-cover change scenarios. Therefore, this model can evaluate and analyze the runoff response to land cover change appropriately.

Abstract:On the base of Graph Theory, free-scale structure viewpoint and vertex degree indices, the paper describes and analyzes numeral and spatial characteristics and their urbanization relationships of drainage structure within the Lake Taihu watershed. Numeral degree of Nanhe drainage structure in Lake Taihu watershed does not accord with power function distribution, but length and rank degrees represent the characteristics of scale-free structure. Additionally Nanhe drainage structure is appropriate for not only Horton First Law and Second Law but also scale-free structure. Scale-free structure really fits a power function, which reflects an imbalance-structure system controlled by few gathered nodes and provides some key methods for identifying and modeling hydrology index of watershed. Lastly the power law behind the drainage structure shows the human disturbance difference exerted on drainage structure. In the highly urbanized area of Nanhe middle stream and downstream numeral and rank vertex degrees are both high, but length degree is low and in the less urbanized area, the area rank vertex degree is also very low. In the upstream area, urbanization level is low and length vertex degree is high, but rank vertex degree is low. The numeral vertex degree of most of nodes is low and has no clear relationship with urbanization.

Abstract:The community structures of macrozoobenthos and bioassessment of water quality in a second order river—Tanqigou stream of Qingjiang River Basin were investigated from April 2006 to March 2007. Altogether 82 species of macroinvertebrates were collected, among which aquatic insects were 70 species, belonging to 45 genera in 27 families under 7 orders. The community structure exhibited an obvious spatial and temporal variations. Site S2 with fringe effect possessed the largest number of species, and most of the macroinvertebrates presented in April with 61 species sampled, more than those in other months. Over 60% of the collected species could inhabit in the six types of microhabitats. Biodiversity in spring was the largest, and followed summer, winter and fall in rank. The density of the community reached its peak in April at 3293ind./m², while biomass attained its peak in December at 163g/m². The water quality was bioassessed with Shannon-Weaner diversity, Biotic Index and Family Biotic Index, and totally it was fairly clean during the sampling period. Considering the coincidence with physical-chemical parameters, BI and FBI bioassessment methods were fitter to apply in this region .

Abstract:Investigations on the phytoplankton were carried out at 10 stations in Anbanghe wetland, a type of cold regions swamp, in summer 2005 and spring 2006. Phytoplankton community classification was undertaken by multivariate analyses, such as cluster analysis and metric multidimensional scaling analysis (MDS).92 common species occurred in both seasons, and 37 taxa and 82 taxa were identified in spring and summer, respectively. In spring the average abundance was 95.26×10⁴ind./L, and in summer was 268.45×10⁴ind./L. Based on the calculation of Bray-Cartis similarity matrix according to species abundance compositions of each station, cluster and MDS analysis showed that three communities can be distinguished in both seasons:(i) the central community, in spring, was Tabellaria flocculosa-Pediastrum tetras community, and in summer was P. tetras community, (ii) the margin community, in spring, was Cyclotella meneghiniana-Synedra acus community, and in summer was Anabaena sp.-Microcystis aeruginosa-C. meneghiniana community, (iii) the lotus flower pond community and Raphidiopsis mediterranea community in spring, and Merismopedia glauce community in summer. Phytoplankton composition, abundance, and diversity of each community were different between spring and summer, and positively correlated to the change of environmental factors between seasons.

Abstract:Lake Wuliangsuhai is a very important part of irrigation and drainage system of Hetao irrigation area. It is also an important migration and breeding ground for Northern China migratory birds. The wetland was listed in in 2002. The present investigation deals with the aquatic status of Lake Wuliangsuhai from April 2004 to January 2005. The study revealed that there were 62 species of zooplankton belong to 34 genera in the lake, which include 16 species of Protozoa belong to 11 genera, 33 species of Rotifera belong to 17 genera, 4 species of Cladocera belong to 4 genera, and 9 species of Copepodo belong to 5 genera. The average abundance and biomass of macrozooplankton were 687ind./L and 3.4985mg/L and Protozoa were 2.508×10⁴ind./L and 0.1254mg/L, respectively. There were 11 species of zoobenthos found in the lake, which belong to 4 families. The average abundance and biomass of zoobenthos were 3031.4ind./m²and 71.67g/m². The abundance and biomass of zooplankton changed significantly with seasons. The abundance and biomass in the Spring and Summer are dramatically higher than in Autumn and Winter. The biomass of zooplankton and zoobenthos were used as indicators of water body status to evaluate the nutritional status and the results showed that the lake was in the status of eutrophication.

Abstract:Water samples were collected by using standard methods at ten locations in Yi River watershed from July 2006 to May 2007. Yi River watershed contains 181 species and varieties, 73 genera, and 7 divisions of phytoplankton, among which Chlorophyta and Bacillariophyta are the most important component. Within the watershed, there are 137 species and varieties, and 7 divisions of phytoplankton in Yi River; 134 species and varieties and 7 divisions in Beng River; 75 species and varieties, and 7 divisions in Dongwen River; 67 species and varieties, and 6 divisions in Meng River; 70 species and varieties, and 6 divisions in Su River; and 80 species and varieties, and 7 divisions in Liuqing River. Water quality assessment was calculated by using saprobic indicator, saprobic indicator commuuity, and phytoplankton general index. Overall evaluation result of Yi River watershed water quality is: Dongwen River, Su River, Meng River, Beng River and Yi River are β-ms, and Liuqing River is α-β-ms. The water quality orders are: Su River> Dongwen River> Beng River> Yi River> Meng River> Liuqing River. Building rubber dams has changed the rearrangement of the water yield in Yi River and Beng River, which has reduced their streams speed greatly and caused the change of phytoplankton community from fluvial facies to the lake facies. However, it has less effect on Dongwen River, Meng River, Su River and Liuqing River, relatively.