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淡水湿地水文过程控制着湿地植被景观的形成与演变.基于Landsat TM/ETM+遥感影像数据，利用决策树分类法提取鄱阳湖湿地1992、1999、2006、2012年4期景观信息，通过景观格局指数、转移矩阵和质心迁移法对苔草景观的空间变化及其与水文过程关系进行分析.结果表明：研究期间，鄱阳湖湿地秋、冬季苔草景观分布面积受到水位和退水过程的影响，低水位年的中滩位缓慢退水与低滩位快速出露更有利于苔草景观的扩张；苔草景观的空间格局与水位关系密切，在低水位年份，低位洲滩提前出露，苔草景观分布高程较低，部分低位光滩被苔草所侵占，原苔草分布的部分洲滩转变为芦荻景观，景观的破碎化程度较重，在高水位年份，低位洲滩长期被水体淹没，苔草景观分布高程相对较高，部分芦荻分布区被苔草所侵占，而原苔草景观的部分区域转变为水体和光滩，由于该期间苔草主要集中分布在湖周和入湖河口地带的高位洲滩上，其景观破碎化程度较轻；水位年际间的升降变化会影响苔草景观质心位置，年均水位上升引起景观质心发生向湖岸方向推进，而年均水位下降则会导致苔草景观质心向湖心方向转移.

Fishery is one of the main functions of Lake Taihu,which plays an important role in improving the water environment. However,it is also influenced to a large degree by the environmenal change.Recently,the main problems facing the natural fishery in Lake Taihu are the over-intensive catching and irrational utilization of natural resources.This paper,based on the data of many years' catches in Lake Taihu,analyzed the community structure of fishes in Lake Taihu and their succession dynamics.According to the fish yields and compositions in different area of Lake Taihu,the natural fishery characteristics and problems were studied.Some ideas were presented to develop the natural fishery based on the present research,such as controlling the fishing gear specifications and catching intensity,adjusting the catching time,regulating the structure and proportion of stocking fish species and developing lake fishery in a reasonable way.Meanwhile,the potential of natural fishery was analyzed on the basis of present biological resources in Lake Taihu.It suggested that the construction of fishery environment and studies on influence of fishery on water environment should be strengthened for the further development of lake fishery.

Distribution of soluble reactive phosphate (SRP) in pore waters is a sensitive indicator showing geochemical properties of phosphorus in sediments. Concentration of SRP in synthetic solutions was obtained based on the principle of diffusive equilibration in thin films (DET). Analytical procedure generally includes equilibration of the gels in solutions or pore waters, section of the gels after retrieval, back elution of phosphorus in the gels, and analysis of SRP in the eluents. Equilibrium and extraction times were determined at 24h and 16h, respectively, with 0.25mol/L HNO3 used as an extractant. Concentrations of SRP in pore waters of different sediments measured by using the established DET technique agree well with its actual values, and the variations are generally within ±5%. Analytical results for sediment profiles with this technique, which has a vertical resolution at about 3mm, also show comparison with those using sampling techniques of Rhizon and Mini-Peeper. The established DET technique was used to measure SRP profiles in sediments of macrophyte- and algal-dominated regions in Lake Taihu. Peak-shape distribution and horizontal heterogeneity of SRP were observed in macrophyte-dominated region, while an upward and increasing movement of SRP was observed in algal-dominated region with an increase in water temperature.

Bellamya sp.snails are very common in Lake Taihu.The effects of snail(Bellamya sp.) on the growth of Hydrilla verticillata Royle and Elodea nuttalli ST John and dissolved nutrition elements were examined in a labo- ratory.After a week of exposure of snail and aquatic plant in a experiment,increments of the per unit of Hydrilla verticillata Royle in three groups were:H:0.475 g,L:0.106 g,C:0.021 g and increments of the per unit of Elode- a nuttalli ST John were H:0.704 g,L:0.663 g,C:0.478 g respectively.In addition,the change of length and node of Hydrilla verticiUata Royle and Elodea nuttalli ST John with snail were higher than those without snail,It could be concluded that the increase of nutrition by snail in water could stimulate the growth of HydriUa verticiUata Royle and Elodea nuttalli ST John,because the metabolism of Bellamya sp.increased the nutrition of water and the primary productivity of aquatic plant were similar in three situations with the same experiment environment.

To study the factors affecting the nutrient release of Bellamya sp. , laboratory simulation experiments were carried out, and other traits of Bellamya sp. such as the effects of Bellamya spp. on suspended substance in the water column, water transparency and phytoplankton in the system were also investigated. Results showed that temperature and the amount of food had great influence on nutrient release of Bellamya sp. At 15℃, the release rates of ammonia nitrogen and phosphate phosphorus by Bellamya spp. were 55.60(±4. 95 )μg /( g·d ) and 2.073(±0.1203)μg/(g·d), respectively; at 25℃, the release rale of phosphate phosphorus was about 2. 819 (±0.075)μg/(g·d). So the release rate of nutrient increased at an enhanced temperature , meanwhile nutrient release rate of snail eating food was higher than it that eating nothing. Bellamya sp. could increase the transparency of water on a short term, but the release of nutrients increased the contents of nitrogen and phosphorus in water, which in turn accelerated the regeneration of phytoplankton. Bellamya sp. can not control the production of algae completely , but their improving the secchi-disk depth of water is helpful for the growth and restoration of submerged macrophytes. It is suggested that the combination of biomanipulation of snails and restoration of submerged macrophyles will be an important technical way to control the eutrophication and improve water environment.