巢湖东部沉积硅藻组合记录的水环境变化

Aquatic Environment Changes Inferred from the Sedimentary Diatom Record in the Eastern Part of Chaohu Lake

对巢湖东部湖心31 cm深的沉积岩芯进行放射性核素定年和化石硅藻分析,根据硅藻属种组合的变化反演了近150 a来巢湖东部水环境变化历史.结果表明,巢湖东部水环境变化经历了2个主要阶段:11827—2000年以Aulacoseira granulata占优势,但1970年其含量(以数量所占比例计)出现一明显谷值(22.4%),同期附生和底栖类硅藻频繁出现,反映了水动力条件减弱后又增强的趋势;该阶段水生植被较为发育,水体维持中营养状态.22000年至今,以A.granulata和耐营养属种(A.alpigena、Cyclostephanos dubius)为优势组合,附生和底栖类硅藻含量显著减少,表明生活污水的大量排放导致湖区急剧富营养化;Hill多样性指数在2000年后显著下降,表明在该阶段水生生态系统发生退化.

Aquatic environmental changes in the eastern part of Chaohu Lake over the last 150 years were inferred with high resolution radionuclide dating from subfossil diatoms preserved in a 31 cm long sediment core. Two distinct stages of environmental changes were identified according to the diatom assemblages. 1） Between ca. 1827 and 2000 AD,the dominance of Aulacoseira granulata was related to strong hydrodynamic conditions. This species showed an obviously small value in quantity percentage around 1970,which could have resulted from weakened hydrodynamic conditions. Meanwhile,the frequency of epiphytic and benthic taxa indicated that the lake was mesotrophic with the development of macrophyte. 2） After 2000,the diatom assemblages were characterized by the codominance of A.granulata and the eutrophic species（ A. alpigena and Cyclostephanos dubius）,with the shrinkage of epiphytic and benthic taxa. The shift in the diatom flora indicates that domestic sewage triggered nutrient enrichment after 2000. The decreased Hill diversity index reflected the degradation of the aquatic ecosystem since 2000.