太湖生态系统的演变与可持续发展

分析了近50年来太湖生态系统的演变动态。随着时间的推移，太湖的化学水质逐渐下降，湖底淤积层厚度逐步增加，浮游藻类的密度不断增大，种类数逐渐减少，且明显趋于小型化。高等水生植物在50年代以马来眼子菜为主，但进90年代以后，随着挺水植物、浮叶植物的逐步扩展，沉水植物的覆盖率和生物量日益降低，湖底的淤积和部分湖区沼泽化的进程加快。从1959年起到80年代后期，太湖底栖动物的密度和生物量均有一定程度的增加。进入90年代后，由于网围养殖的迅速发展和过度捕捞，软体动物的资源量急剧减少。太湖的渔业总产量一直呈上升趋势，自1983年网围养殖出现后，网围养殖经历了从粗放粗养型到精养模式的过渡，由常规养鱼向特种养殖的转化，从污染量大到污染量小的方向发展。目前必须加强太湖的综合治理，进行生态修复与重建，使太湖生态系统的演变向资源可持续利用的方向发展。

Ecological Succession and Sustainable Development in Taihu Lake

The trend of ecological succession was studied for the past 50 years in Taihu Lake. With the passage of time, the water quality has been worsening and sediment thickening, while the density of phytoplankton has been increasing, species richness decreasing with the smaller species becoming dominant. The trophic status shows the tendency from meso- eutrophic type to near eutrophication. Potamogeton malialaianus was the dominant species of submerged plants in 1950s, but the rate of swamp forming is more rapidly due to the increasing sedimentation and rapid growing of emerging plant and leaf- floating plant after 1990s. Density and biomass of benthos raised from 1959 to 1989, but natural resources and biomass of mollusca reduced after 1990s rapidly because of pen fish culture and excessive catching, total yield of fisheries continued to raise. Since 1984, pen fish culture converted from extensive models to intensive ones, the culture species were shifted from regular species to high valued species, from heavy pollution and environment- hostile to ecological types. The comprehensive control and ecosystem rebuilding in Taihu Lake must be emphasized and carried out so as to maintain the sustainable development of lake resource.