Abstract:This paper reviews three hot topics associated with Lake Taihu environmental and ecological researches in the recent ten years, i.e. hydrodynamics and its effects on the lake environment and ecosystem, lake sediment and internal pollution loadings, lake ecological structure and functions related to algal bloom. In the aspect of hydrodynamics and its effects, a field approach to investigate the relationships between hydrodynamic parameters and environmental factors was developed. We found hydrodynamical intensity quantitatively related to sediment erosion and suspension, and further related to the transparency, internal loading and oxidation-deoxidization conditions at water-sediment interface. The internal structure of hydrodynamics in Lake Taihu has been achieved, so that the necessity of three dimensional hydrodynamic model has been built instead of two-dimensional hydrodynamic model for this large shallow lake. Relation functions of light penetration and intensity distribution as well as transparency related to seston have been established. Primary production estimate model of Lake Taihu based on the seston has been developed. In aspect of sediment and internal loading, the distributions of sediment and the pollutant in sediment have been clearly revealed. The main force which makes sediment resuspension was identified. The effects of hydrodynamics on the sediment resuspension and further on the nutrient releasing were investigated. A conceptual mode of nutrient releasing for large shallow lake was proposed and the criteria for internal loading control were put forward. In aspect of lake ecosystem and algal bloom, based the hypothesis of algal bloom formation, the understanding of algal bloom formation has been improved via the findings of nutrient thresholds and restoration ofdormancy algal spores. Investigations also revealed the phenomena that eutrophication leads to degradation of ecosystem and biota tends to small sizes. The nutrient cycling will speed up and more available nutrient will be imported which in turn enhances the eutrophicating. After investigation of periphyte effects on the submerged macrophyte, the mechanism on macrophyte disappearance was clarified. Based on these findings, new idea on eutrophic lake control and ecosystem restoration was proposed, i.e. reducing the nutrient loading firstly and restoring ecosystem secondarily. Finally, the paper made perspective for the future development of these aspects.

Abstract:The purpose of this study is to investigate changes in sedimentary environments in Lake Dianchi, a shallow water lake on the Yun-Gui Plateau. Overall characteristics of organic matter values, including δ¹³Corg, δ¹³N, C/N and TOC, from a 63cm-long core from the center of the lake were analyzed. Concentrations and stable carbon isotopic compositions of the bound fatty acids are also analyzed and compared with those of the corresponding free fatty acids. The results indicate that the past environment changes recorded in the modern sediments in Lake Dianchi can be divided into three main stages. Values of δ¹³N and TOC increased during the latest stage of the 0-20cm interval and were related with the eutrophication process of the Lake Dianchi, when concentrations ofbound fatty acids and free fatty acids range from 38.5-209.6μg/g and 12.0-318.1μg/g, respectively. Compared to free fatty acids, bound fatty acids in the sediments of Lake Dianchi have more abundant unsaturated fatty acids, iso- and anteiso-branched fatty acids, indicating that they predominantly sourced from the plankton and bacteria and were more resistant to the early chemical and biological degradation. Multiplying of the plankton and bacteria caused the speeding up the lake eutrophication processes. Changes in the δ¹³C value of the bound nC16:0 fatty acid were recorded well in Lake Dianchi sediments and provided good information of the enhancement of lake eutrophication in the recent few decades. Therefore, it will become an important indicator reflecting the lake hyper-eutrophication.

Abstract:A laboratory experiment for studying the effects of sediment dredging on denitrification process was carried out through a one-year incubation of undredged sediments (control) and dredged sediment cores. Denitrification rates in the sediments were estimated by means of the acetylene blockage technique. During the experiments, the denitrification rates in the undredged and dredged sediments ranged from 21.6 to 102.7nmol/(g·h) and from 6.9 to 26.9nmol/(g·h), respectively. The denitrification rates in the undredged sediments were significantly higher (P < 0.05) than those in the dredged sediments throughout the incubation period, with an exception of February 2006. The relative importance of various environmental factors on denitrification was assessed, and the results indicated that denitrification rates in both undredged and dredged sediments were regulated by temperature controls. Nitrate was likely to be the key factor limiting denitrification rates in both undredged and dredged sediments. Organic carbon played some role in determining the denitrification rates in the dredged sediments, but not in the undredged sediments. Potential denitrification in the early dredged sediments couldn't reach a high rate as that in undredged sediments, which should be considered as a potential negative effect for nitrogen removal.

Abstract:Volumetric oxygen exchange rate (O₂(t)), based on measurement by a flow-on/flow-off controlling method, is significantly correlated with TOE (total oxygen exchange) obtained from laboratory-incubated sediment cores. The difference between TOE and DOE (diffusive oxygen exchange in diffusive boundary layers) suggested that there is a fauna-mediated O₂ consumption in the two factors. Comparison of DOE with DOEs (diffusive oxygen exchange in sediments) from one-dimensional oxygen concentration profiles at a steady stationary condition, O₂(t) as well as TOE, is an integrated measurement for the diffusion, advection and fauna-mediated O₂ consumption. Furthermore, a comparative study of TOE values among sediments from Lake Taihu and Lake Nansihu revealed that the difference from the sites was due to the variation of organic matter concentration in the surface sediments, additionally effects of benthic faunas.

Abstract:Contents of enzymatically hydrolysable phosphorus (EHP) in particle and colloidal phases in Lake Taihu were analyzed. Colloid in lake water was separated by tangential flow ultrafiltration, which included the component with diameters from 1nm to 1000nm. The EHPs from Wangyu River, a large water channel connected Lake Taihu with Yangtze River, and from Lake Qiandao and Fuchun River were also studied. Mean of particle EHP (particle size larger than 1000nm) accounted 58% of total EHP, which was the main contributor in the water. Mean of colloidal EHP accounted 35% of total, which also shows a high ratio compared to the true dissolved phosphorus. During the investigation period, total phosphorus and EHP in Wangyu River were 0.216mg/L and 0.174mg/L, respectively, suggesting that there is a high ecological risk to pump too much Yangtze River water to Lake Taihu. In Lake Taihu, percentage of micro-size colloid in marcophyte dominated zone (Xukou Bay) was much higher than that in cyanobacteria dominated zone (Meiliang Bay).

Abstract:In order to investigate the spatial variations of the over-winter cyanobacteria in different areas of Lake Taihu, sediment and water samples were collected monthly in 14 sites in winters from 2007 to 2008. The phycocyanobilin concentration (PC) of samples was measured by the fluorometry analysis of pigments to confirm the difference of PC's spatial variations among three areas of Lake Taihu. The result shows that, differing from summer, the winter PC in both sediment and water from northern part was lower than western and southern part of Lake Taihu. Even in December, in some parts of western and southern areas the cyanobacteria was still blooming, and PC of surface sediment was also high. According to the result, it is clear that the over-winter cyanobacteria was mainly distributed in western and southern areas of Lake Taihu during the investigation winter seasons.

Abstract:Experiments were carried on by using four dominant species of Microcystis of Lake Taihu, including Microcystis aeruginosa 905 (toxic), M. Aeruginosa 469 (non toxic), M. flos-aquae 1028 and M. Wesenbergii 929, grazing by Ceriodaphnia cornuta cultured in a modified BG-11 medium (TN=10mg/L, TP=0.4mg/L) with over 12 day tests. No large colony (above 10 cells) formations in M. Aeruginosa 905, M. Aeruginosa 469 and M. Wesenbergii 929 were observed in the controls and treatments except for M. flos-aquae 1028. The cells proportion of large colony of M. flos-aquae to total cells was significant different between controls and treatments, contributing 22% in controls and 53% in treatments. There were significant differences between controls and treatments in M. flos-aquae in density of different units of unicell, two-cells, small colony (3-10 cells) and large colony. Significant differences were found between controls and treatments in the number of cells per large colony of M. flos-aquae from day 6 to day 12 in the experiment. Our results showed that large colony of M. Aeruginosa 905, M. aeruginosa 469 and M. Wesenbergii 929 can not be obtained by grazing in the C. Cornuta, but C. cornuta is one of important factors in enlarging colony formation of M. flos-aquae.

Abstract:Pollution of Caoqiao River in Taihu Basin has become one of increasingly serious problems, which affects sustainable development of this region. A model was constructed based on the characteristics of the small watershed and segmentation of water polution, and applied to calculate the capacity of the water environment and the quantity of pollutants reduction. In this case, it is proposed a segment control pattern of river pollution and a water environmental capacity control pattern of watershed management. An operational plan for controlling nitrogen and phosphorus in rivers was established, thus the key project and the annual measurement were decided, and the annual reduction plan of pollution source was implemented, which has provided the scientific basis for better management of pollution control for small basin.

Abstract:TN/TP ratio represents the nutrients structure for phytoplankton in aquatic ecosystem. Observed data of TN, TP and TN/TP ratio from March 2007 to March 2008 in Xiaojiang backwater area in Three Gorges Reservoir were summarized in the paper. It was found that mean value of TN is 1553±43μg/L, while that of TP was 61.7±2.7μg/L. Although both TN and TP showed remarkable seasonal variability, their variations were approximately the same. Generally, they were low in early spring while suffered a sharp increase in the late spring and reached a maximum level in the summer due to the frequent storm. Concentrations of both TN and TP decreased in the autumn while increased again in the late winter. Average ratio of TN/TP was 30.6±1.4 and indicated a phosphorus-limitation in the XBA generally. The significant positive correlation between TN and TP indicated that both nutrients might have the same importing and exporting approaches to the water area. TP was major nutrient that controls TN/TP level. When TN/TP≤22, nitrogen is control factor and the relatively intensive TP input can result in the decrease of TN/TP ratio. Nitrogen fixation might occur to overcome the surplus phosphorus in water column. When 22＜TN/TP＜32, TP manipulated nutrients that controlled the TN/TP ratio. It was also anticipated that the organic anabolism loop from nitrate to PON might be the dominant process in nitrogen organic anabolism. When TN/TP≥32, low TP would considerably prohibit the organic anabolism process, while ammonia might become the potential significant factor that impacted on the pattern of nitrogen cycling. It was suggested that due to the relatively short hydraulic retention time in XBA, nitrogen cycling would not be influenced by TP but also impacted by the hydrodynamic condition. Intensive nutrients loadings that increased TP were due to the relatively heavy precipitation and surface runoff in XBA, followed by the unstable physical living environment for planktonic communities, while the decrease of TP indicated the feasible living environment, stimulated the organic anabolism process of nitrogen.

Abstract:Water quality of West Lake has been greatly improved after implementation of lake restoration projects, such as sediment dredging, wetland reconstructing and water freshening supported by Hangzhou Municipal Government since 1998. Based on continuous data analysis of chlorophyll-a concentrations in West Lake from 1998 to 2007, the chlorophyll-a concentrations in main area of West Lake in 2007 decreased by a range from 42.8% to 87.3% compared with those in 1998. The results showed that the restoration projects played a major role in water quality improvement of West Lake.

Abstract:Based on the comparative studies between the enclosure culture situations of different density and scale of water environments investigated during period from March and December 2007 in East Lake Taihu, the paper analyzed the economical benefit and environmental effect under different culture models. The results showed that culture models of bait casting and monoculture in East Lake Taihu, no matter which kinds of density and scale there were, would make the output of nitrogen and phosphorus nutrients less than the input, and mass-input of exogenous nutrients would cause pollution effect on water quality. An estimation of nutrient contributions in three enclosure crab culture areas A, B and C showed that 1kg crab production has created 0.24, 0.33 and 0.30kg nitrogen and 0.043, 0.059 and 0.051kg phosphorus into the lake, respectively. According to the comparisons of environmental situations of economic benefit and growth specification of the enclosure crab culture in East Lake Taihu, a reasonable density of the optimized model is 6000 crab/ha and the single enclosure is 2.33 ha/each, while the current culture manner should be improved. For too large scale and unreasonable distribution of enclosure culture in East Lake Taihu, we suggest that the area of enclosure crab culture should be controlled under 3165.2 ha.

Abstract:Effects of groundwater depth on germination and seedling growth of Acorus calamus were studied by simulating experiment. The experimental barrels (diameter of 35.5cm and depth of 100cm) were filled with fluvial sands of 80cm depth. The water was introduced directly into the bottom of the barrels to build the groundwater depths in -60cm, -50cm, -40cm, -20cm and 0cm in different five barrels respectively. The same rhizomes of A. calamus were selected and planted in each barrel. The results were as follows: (1) Groundwater depth has significant effects on germination and seedling growth of A. Calamus. The plant can germinate in the groundwater depth from -60cm to -20cm, when groundwater depth decreased germination ratio reduced. On the 70th day, germination ratio of the -20cm treatment reached 90%, which were 2.25 and 3 times of those in the -50cm and -60cm treatments. Plant of 0cm treatment can not germinate. (2) Leaf length, width and area were positively correlated with groundwater depths and the significant correlations are able to be accepted (P < 0.01). With decreasing of groundwater depth, the number of the laminae reduces. The number of the laminae in -20cm and -40cm treatments were very significantly higher than those in -50cm and -60cm treatments (P < 0.01). Groundwater depth of -60cm was greatly affected on survival of plant seedling since plant seedling of -60cm treatment began to die after the 70th day. (3) With decreasing of groundwater depth, Chl.a, Chl.b and Car reduced but Chl.a/b increased. Plant leaves captured the light reducibly by the way of morphological adjustment and chlorophyll content reduction. (4) The laminae MDA and membrane permeability increased, which is led by low soil water content caused by low groundwater depth. (5)Groundwater depth has great effects on the rapid responded light-curves of A. Calamus. As groundwater depth decreases, the maximal photosynthetic electron transport rate (ETRmax) and the minimal saturated light intensity reduce, and the responded photoresponse capacity is weakened.

Abstract:Suzhou Creek is an urban river across Shanghai City and its adjacent areas. In the present study the river environmental quality was assessed based on fish communities. The specimens sampled in the year 2001 were compared with those collected in Shanghai Science and Technology Museum (formerly Shanghai Museum of Natural History) in the 1960s. The number of species decreased from 62 in the 1960s to 44 in 2001, with the most prominent decrease in the species of Gobioninae that are benthos and insectivores. Marked change was also seen in trophic dominance. Percentage of species as piscivores decreased from 27.4% in the 1960s to 22.7% in 2001, and insectivores from 24.2% in the 1960s to 11.4% in 2001. On the other hand, the percentage of species as omnivores increased from 25.8% in the 1960s to 38.6% in 2001 and turned to be prominent dominance. The diversity of species in the upper stream is higher than that in the downstream. Such changes indicate that the food web was simplified and the biological integrity was decreased. It is inferred that the creek substrate degrading has caused the changes in the habitats of the aquatic creatures in Suzhou Creek.

Abstract:Community structure of macrozoobenthos and the bioassessment on water quality in a second order river—Hujiaxi Stream of Qingjiang River basin were investigated from April 2006 to March 2007. The results showed that, among collected altogether 87 species of macroinvertebrates, there were 3 species of Annelida, 3 species of Mollusca, 76 species of aquatic insects, and 5 species of Malacostraca. The community structure exhibited obvious spatial and temporal variations. The species number reached its peak in June, and descended to the lowest in December. There was the largest species number in Site 5, and more species macroinvertebrates were presented in June than those in other months. Over 75% of the collected species could inhabit in all six types of microhabitats. The density of the community reached its peak in April at 3293 each/m², while biomass attained its peak in December at 163 g/m². The water quality was bio-assessed with Shannon-Weaner diversity, Biotic Index (BI) and Family Biotic Index (FBI), and results showed that the river water was fairly clean during the sampling period. Considering the coincidence with physical-chemical parameters, BI and FBI bio-assessment methods were much fit to apply in rivers of China.

Abstract:Survey aiming at the wild fish resources in Provincial Rare Fishes Natural Reserve of Xijiang River in Zhaoqing City. 81 fish species belonging to 11 orders, 25 families and 69 genera from 2006 to 2008, among them there are 8 river-sea migratory species, 6 exotic species and 67 native freshwater species. Analysis of the species numbers and diversity indices showed that fish diversity of the Reserve was high. Cirrhina moitorella, Squaliobarbus curriculus and Megalobrama hoffmanni were the preponderant species. Megalobrama hoffmanni, Squaliobarbus curriculus, Cirrhina moitorella, Xenocypris davidi and Clupanodon thrissa are the primary economic fishes. The rare fishes such as Anguilla marmorata, Cranoglanis bouderius bouderius, Parabramis lineatus and a lot of species only distributed in Pearl River water system can be seen there. The fish stocks of the Reserve belong to different ecological types in their migration, feeding and inhabitation. Fish communities were dominated by sedentary species (72.8%) of the community, omnivore species (51.9%) and sub-stratum species (50.6%). Xijiang River Rare Fishes Natural Reserve is perfect area for fish living due to its special hydrodynamic environment and complicated riverbed geology. Habitat destroying and excessive catching are the key factors to impact decreases of the fish diversity.

Abstract:The heavy metal concentrations (Cu, Pb, Zn, Cd and Cr) in sediments from core XJ2 in Lake Xijiu, Taihu Basin were investigated, and the characters of their temporal distributions were studied on basis of geo-chronological results. Approach of the potential ecological risk assessment proposed by Hakanson was applied to investigate the history and the relative potential ecological risks of heavy metal contamination of lacustrine sediments. The results showed that the sediments were polluted by Cd element far more serious than the rest four elements, so that Cd element was the main factor in heavy metal contamination. From the early 1900s, the heavy metal contamination of sediments and the potential ecological risks increased remarkably. The most serious period, when the contamination of all the five heavy metals reached their “very high” level, was during the middle 1990s. The indexes of potential ecological risk dropped afterwards because a result from the adjustment of industrial structure and closing of some heavy contamination factories by local government, although the contamination conditions and the potential ecological risk were remaining at the “very high” level in 2004.

Abstract:Hydrological modelling of surface runoff for Lake Poyang watershed is of significant importance since the surface runoff is the main source of water inflows of the lake. The hydrological model can be used to reveal the influences of changes of natural and human conditions in the watershed on the surface runoff and consequently on the water balance of the lake. Hydrological modeling of the Lake Poyang watershed is challenging due to the complexities of the system, e.g. the large size (162.2 ×10⁴ Km²) of the area with high heterogeneity of soil types and land uses, contribution of stream flow from multiple rivers to the lake, and the overland flow at lake-side zone. Relevant methods to simulate the above features were presented and a distributed hydrological model was developed in this paper for Lake Poyang watershed. The model was well calibrated and validated against the observed daily stream flows at six stations from 1991 to 2001. The results were satisfactory inthe general model predictions, with high monthly efficiencies of 0.82-0.95 for Ganjiang, Xinjiang and Raohe rivers. Accuracy of model prediction for Fuhe and Xiushui rivers was slightly lower, with efficiencies ranging from 0.65 to 0.78. The model indicated that the average volume of annual surface runoff to the lake for the simulation period was 162.3 billion m³, of which Ganjiang, Xinjiang and Fuhe rivers contributed 47%, 13% and 12%, respectively. Direct overland flow to the lake at the lake-side zone accounted for about 4%. The rest (24%) was contributed via Raohe, Xiushui rivers and several tributaries. The model successfully simulated the hydrological processes of Lake Poyang watershed, and can be used to evaluate impacts of human activities on water variability and water balance of Lake Poyang.

Abstract:Tree-ring width chronologies of Sabina Tibetica were constructed based on tree-rings of 1061-year sampled in Tianjun county of Lake Qinghai Basin. The response function analysis showed that the chronologies were sensitive to the annual precipitation so that the paper reconstructed annual precipitation series. The cross-validation method was used to check in the stability of the calibration equation, and the result indicated that the equation was stable and the variation of reconstructed annual precipitation was dependable and representative. There were six years showing precipitation below normal stage, which were periods of 1001 to 1060, 1131 to 1320, 1411 to 1510, 1691 to 1740, 1811 to 1850 and 1911 to 1940. There were seven years that showed precipitation above normal stage, which were period of 961 to 1000, 1061 to 1110, 1321 to 1410, 1511 to 1650, 1741 to 1790, 1881 to 1910 and 1941 to 2000. The occurrence of abrupt precipitation was once a time every 53 years．Reconstructed precipitation series showed an unstable period from the 13th to 14th centuries, but stable periods in the 12th, 17th and 20th centuries.

Abstract:Water level in Lake Qinghai, a representative inland lake in northwest China, is declining rapidly under the influence of climatic change. At the same time, the environmental problem becomes more serious. It has arrested many people's attentions. In this paper, the stream flows for period until the year of 2050 are estimated by multiply linear regression and the trends of the water level are forecasted based on an improved model of hydrologic and energy balance. The prediction indicates that the water level would keep steadily about 3192.7m before the year of 2020, and then continues to decline. It would drop to 3191.22m in 2050. Changes of the water level in Lake Qinghai would become alleviative in the next several decades of 2010-2050.

Abstract:Characteristic of water scattering is very important for researches on water color remote sensing and aquatic ecology. The inherent optical properties of water samples collected in Lake Taihu from Nov. 8 to Nov. 21 in 2007 were analyzed, and the scattering characteristics and relative factors were researched. The results showed that, the scattering coefficient was reduced with increasing wavelength according to power function. The average power index is -0.82±0.21, and the variation coefficient is 25.39%. Both slope and power of the particle size distribution function are linearly correlated with the scattering coefficient of ln(550nm)/ln(756nm). The correlation coefficients (R²) are 0.894 and 0.783 respectively. Negative correlation between the backscattering rate and the concentration of inorganic suspended was found and R² was 0.854. Correlations between refractive index and the inorganic suspended solids concentration and between the ratio of inorganic and organic were negative, and the coefficients (R²) were 0.851 and 0.781 respectively.