Abstract:Human activity is one of most important factors that affect the change of environmental proxies in lake sediment records during the historical period. In this paper, based on the analysis of multiple proxies (graim size, organic carbon, magnetic measurements and radiometric methods) and historical document records, the history of water-level fluctuations and the changes of human activities were reconstructed in Dachahu Lake area, the west part of Poyang Lake, the largest freshwater lake in China during the past 2 ka and probed into the linkage between human activities and environment changes. The studies show that there are striking responses in magnetic records to human activities and grain-size records to water level fluctuation documented by historical record. The following processes that the lake have undergone may reveal the corresponding changes of human activities or land use from lakeshore to hillside area in historical times. (1) Before AD 155, the environment of this area was fluvial depression or small shallow pond and sightly influenced by human activities. (2) In AD 155—480, the water level of Poyang Lake expanded southwards and the large water surface formed gradually, which provided good condition for the development of agriculture in the area and the impact of human activities was greatly enhanced. (3) After AD 480, the extension of Poyang Lake was at its climax, which forced human being withdraw from lakeshore area and turned to exploit hilly land. The alternation also caused the increase of soil erosion processes and the development of exploit delta in Poyang Lake quickly. (4) From AD 955 to 1180, there was a short dry period and water level began to descend, resulting in huge wetland formed and the increase of human activity in lakeshore area. (5) About AD 1545, the water level of Poyang Lake rised again because the outlet of the lake to the Changjiang River was obstructed gradually by he development of shoals. (6) During last 200 years, especially since the 1950s the greatest changes in evnironment proxies occurred due to the drastic increase of human activities, such as reclamation and deforestation on a large scale. The result is helpful for interpretation of the process of controlling the change of human aca-tivities in great shallow lake area.

Abstract:Nine sediment-water columns were taken from three stations of East Taihu Lake (about lm in depth) in June, 1997. The overlying water of the cores was filtered (0.45μm), and then the cores were placed in a dark room for 50 days. Air-bubbling was used to keep oxidized conditions in the overlying water and upper sediment, without resuspending the sediment. The room temperature was between 23.5 and 31.2℃ , and the pH value of the overlying water and upper sediment was 7.2±0.2. Concentration of PO₄^3--P in the overlying water was measured every 2 or 3 days to follow the P-release process. In the first 15 days,PO₄^3--P level in the overlying water increased 2 orders of magnitude. But in the following 33 days, the PO₄^3--P level decreased 1 order of magnitude and then stabilized. Such a process was also found in the West Lake, Hangzhou and Gehu Lake, Changzhou. We think it not a normal sediment-P-release process, but more complex as follows. In natural conditions of East Taihu Lake, the sediment is covered by a layer of detritus. Biological degradation is so intensive in this layer that PO₄^3- accumulates to a high level and diffuses to both the overlying water and the sediment beneath it. In the sediment a steep PO₄^3--P concentration gradient forms because of the high diffusive resistance. But in the overlying water, PO₄^3--P is used by aquatic plants and is kept at a low level. We are not able to measure PO₄^3--P concentration in the detritus layer, but an indirect evidence was found in the same lake: a PO₄^3--P concentration gradient from 200mg m^-3 in the upper sediment layer to 80mg m^-3 in the sediment of 18cm depth existed when PO₄^3--P concentration in the overlying water was only 22 mg m^-3. In the core experiment, phosphorous biological cycling was broken when phytoplankton was removed from the overlying water by filtration, and thus, PO₄^3- accumulated in the water quickly. After 15 days, the P-release reaction in the detritus layer was about to end, and P-diffusion from overlying water to the sediment triggered. In East Taihu Lake and the other similar lakes with stable bottom conditions, detritus layer may exist and affect P-release core experiment seriously. In such a situation, it is better to measure internal-P-loading by other means, such as whole lake P-budget and in-situ enclosure experiment.

Abstract:It is widely accepted that the lake water level will descend in the northwest of China in the near future. Because most of lakes in northwestern China belong to closed basins, the descent of water level often results the condensation and salination of the water, bringing about a series of environmental problems to the lakes and the catchment areas. A calculation based on the analysis of climate, runoff, water balance and water level in Daihai Lake basin shows that the total fall-down of water level is 3.85 m during 1955 to 1995, among which human factor occupies a drop of 3.17 m. It is very clear that human activities give very strong impact on the water balance of Daihai Lake.

Abstract:By using of ARC/INFO and varied information, pictures, data from (1) the map of Taihu lake basin's topography (1 :200000) by Nanjing Institute of Geography, Academia Sinica; (2) the map showing the velocities of the recent crustal vertical movement in the Yangtze River and its adjacent area by Hu Huiming, Huang Liren and Yang Guohua^[3] ; and (3) the forecasting of absolute sea level changes in the front of 21st century by Zhu Jiwen and Xie Zhiren^[4]', this report has build up the Geographical Information System about the sea level of the China' s Eastern sea coast region and ground changes of Taihu lake basin. The results forecast four different rise of sea levels (RSL) under aboslute sea level changes in the early 21st century, as well as the lowering of the high tide of Taihu lake basin correspondingly (i.e. 2000a, 2025a, 2050a). All of the forecasting results will not only be demonstrated by screen, but also be drawn and printed. The GIS supplies the fundamental data and analytical service about the sea level and ground changes of the Taihu lake basin.

Abstract:From the point of environmental vulnerability, the formation and developmnet of Taihu Lake environmental vulnerability are analyzed. It is found that Taihu Lake is a typical ecotone in China, and the tendency of vulnerability will possibly be reinforced in the future. It is necessary to break away from the ideas such as “the paradise in the world” and “the land of rice and fish”. Based on the character of Taihu Lake environment, the controlling countermeasures of vulnerability are put forward.

Abstract:This paper deals with the impact of Hg²⁺, Cd²⁺ on chlorophyll contents and scarenging systems of activated oxygen in stems and leaves of Brasenia schreberi winter bud. The results indicate that, as increasing of the concentration of Hg²⁺ and Cd²⁺, chlorophyll contents, chlorophyll a/b values and soluble protein contents decreased, the activities of SOD and CAT increased first and decreased afterwards and the activity of POD increased from beginning to end. The results also show that Brasenia schreberi winter bud is more sensitive to Hg²⁺ than to Cd²⁺, its leaves is more sensitive than its stems.

Abstract:Using artifical sewage to culture the single-celled agela (Scenedemus obLiquus Turp) until the biological abandance up to 1.7×10⁴ individual· ml^-1, the river snail (Cipangopaludina sp.) and water fleas (Daphnia obtusa Kurz) were inoculated into the sewage. The population dynamics of the algae and water fleas were described. The results were summarized as follows. (l)The changes of the alga density by times were shown to be exponential function. (2) In the still culture stage without harvest, the population growth curve of Daphnia obtusa Kurz was shown as: InN =-0.06410+0.44041; (3)During the stage of interval harvest, the equation of accummu-lated yield was shown to be diplo-logarithmic function:InN = 0.2836+2.5537 Int. (4)The compositions of nitrogen, phosphorus, carbon of the sewage were analized as the feedback culture decreased 80.60%, 72.40% and 45.70%, respectively.

Abstract:Molting process of E. sinensis juveniles in laboratory and the habitat, illumination and temperature in relation to molting in an earthen pond were studied during July to August, 1993. In-termolt cycle of crabs is divided into five stages (Stage A, B, C, D, E). For individuals with body-weight of 0.5-2g, stage A lasted about 2h, stage B about 15h, and stage E about 3-6h. The number of cast integuments perm 2 from weed-growing bottom was significantly greater than that from weedless bottom. Experiment shows that all the crabs molted normally at water depth of less than 2.0m. Diel variations in molting every four hours were observed, indicating that massive molting occurred at 07:00-11:00. Analysis of covariance (water temperature as covariate) suggests that the number of cast integuments every four hours in daytime (07:00-19:00) was significantly higher than that at night (19:00-07:00) (F_1,30=13.4, P=0.0009); the changes in diel water temperature (28-35℃) did not affect molting (F_7,11= 1.99, P=0.1467). Studies also show that crabs initiate molting at water temperature of about 14℃ and molt normally until 35℃.

Abstract:Samples were collected monthly from Xujiahe Reservoir from April 1992 to May 1996 and the ovarian development and spawning pattern in Neosalanx pseudotaihuensis Zhang were described. A histological analysis of oocyte development in N. pseudotaihuensis shows that the fish spawns serially. A six-stage maturity scale, based on both external morphology and oocyte composition, was proposed to classify ovarian development in N. pseudotaihuensis. Monthly trends in stages in ovarian development with the size and maturity of oocytes indicate that spawning extended from March to May and peaked between mid-April and mid-May. Histology of ovarian shows that N. pseudotaihuensis produced clutch-es of eggs, which were released at intervals. Data on length-frequencies and gonads shows that N. pseudotaihuensis typically died in a few weeks after last spawning.

Abstract:Daphnia obtusa Kurz were cultured in 3 kinds of carbonate hard water, treated by micro-algae (Scendesnus obliquas Turp). The water fleas were harvested in two ways-interval and inoc-ulalting harvests. The results were shown as follows after comparison. In the presence of the algae severed as the pioneer organisms in the water, the water fleas could be inoculated. During the still culture stage without harvest, the population growth curves (N) show that N_c(in the improves fish-farming sewage) > N₀(in the pure fish-farming sewage) > N_i(in the improved ground water). During the stage of interval harvest, the mathematical functions of yield (the regression of the general number ranks accumulated from original data gathered each time) in the three kinds of culture medium were all shown to be Logistic growth curve and the population yields shown as N_c N_i N₀ and during the stage of noculation harvest: N_i N_c0 N₀.

Abstract:This study deals with the growth characters and pure culture of Microcystis from Taihu Lake. It is found that Microcystis flos-aquae can grow in solid medium. The results also show that both phosphorus and nitrogen play an important role during the growth period of Microcystis flos-aquae. The maximum growth rates appear when the PO₄^3- concentration reach 1.7 mg·L^-1 and the TDN concentration reached 17 mg·L^-1. Comparing the indoor culture of Microcystis with the Microcystis in the lake, there is a clear difference in their growth characters. The Microcystis in the lake normally appears as big colony while it appears only single cell or small colony with ten cells in indoor culture.

Abstract:The postembryonic development characteristics of Megalorama skolkovii at different stages are described and illustrated. The results show that some features such as the development of air bladder, melanophores, ventral "rift" and time of scale appearance differed from other fishes of Cyprinoid familyl. It can be divided into 15 stages according to the stage development theory of teleosts. The technical measure in fry and fingerlings production was put forward in terms of the postembryonic development characteristics of Megalobrama skolkovii.

Abstract:Pen culture has been widely developed in most frestwater lakes in China and a higher fish yield of 7500 kg/hm² was achieved in some grass-type lakes during the implementation of the 8th Five-year Plan. In East Taihu Lake, the fish yield has now kept increasing with the increase of stocking fingerlings, feeding rate and collecting aquatic weeds, but such practice leads to the unbalance of nitrogen and phosphorous budget and causes a negative impact on the aquatic environment. However, it is somewhat difficult for the government to conduct an effective measurement to control the practice for the time being because of its benefits for the fish farmers. Hence, it is necessarily important to study the ecological practice of pen culture in the grass-type lakes for the proper maintenance of natural resources and protection of the benefits of fish farmers. The study was conducted in Miaoguan, East Taihu Lake with a total pen area of 10 hectare (hm²), where crab and fish were polycultured. In this study, both nitrogen and phosphorous elements were negatively increased through the proper control of feed loading during the culture period . This practice was considered as an ecological cultural model for the sustainable aquaculture development in lakes. The experiment was conducted to study the effects of polyculturing fish with crab in pens on the level of nitrogen and phosphorous in the lake water. With the calculation of input and output of nitrogen and phosphorous during the culture, the experimental results show that the model of polyculture of with crab in pens did not increase the level of nitrogen and phosphorous in the lake water, but it partially reduced their levels instead. During the whole production season, the input of nitrogen and phosphorous by both stocking of fish and crab seeds and loading of feed was 27. 889kg·hm^-2 and 4.381 kg·hm^-2, respectively; while the output of nitrogen and phosphorous by harvesting of fish and crab was 41.177 kg·hm^-2 and 5.801 kg·hm^-2, respectively. As a result, the level of nitrogen and phosphorous could be reduced at a rate of 13.288 kg·hm^-2 and 1.420 kg·hm^-2, respectively from pen culture in the lake. In conclusion, such culture model may result in ideal economic efficiency, low impact on the community of aquatic organisms, thus favoring the sustainable development of pen culture in lakes.

Abstract:Phosphorus from agricultural non-point sources has been identified as the main cause of freshwater eutrophication throughout the world and contributes a large share to the water quality deterioration. With excessive amount of phosphorus being input to the agro-ecosystem, the accumulation of P in cultivated soils has increased the potential for P loss in agricultural runoff and drainage. This paper attempts to summarize the research activities focused on the build-up of P in soil, the interaction of P with soils and its transport in surface and subsurface drainage. Phosphorus indexing system (PIS) used for identifying sites vulnerable to phosphorus loss in agricultural runoff is introduced. Widely practiced mitigation options include untrient budgeting, input management, soil conservation, land use management and the establishment of vegetated riparian zones, buffer strips and sedimentation ponds which have been proved to be very cost effective in a Chinese context.

Abstract:The development of speciation and fractionation schemes of phosphorus from various sediments were outlined together with the elucidation of the advantages or disadvantages of the schemes, and the ecological significance of different forms of phosphorus; suggestions for further researches were presented in this field. They can be of great help to the relevant researches that have been less conducted in China.

Abstract:Large-eye-larva of Chinese crab(Eriocheir sinensis) originated in the Yangtze River can be raised to adult in 141 days under an industrialized stable water temperature while the conditions of nutrition and water quality should be met up with. Its weight can be higher than that of the two-year-old Chinese crab rasied usually in ponds. The rate of mature of the industrially-cultured crab is up to 89% which can be used for artificial breeding.