天鹅洲长江故道近代环境变化的有壳变形虫记录

Recent Environmental Changes in the Swan Oxbow of the Yangtze River: Evidence from Testate Amoebae Records

通过对天鹅洲长江故道近代沉积物中有壳变形虫的形态、生态特征和多样性组合变化的研究，重建了该地区30a以来有壳变形虫的群落演替过程。沉积物中有壳变形虫和色素分析结果表明，天鹅洲长江故道的生态与环境在人类活动和河道变迁的影响下发生了较为深刻的变化，即：①1975～1987年，水位较低，接受较多的外源有机物质，营养水平上升；②1987～1994年，水体稳定，水质变得清澈；③1994～2001年，自然保护区建立以后，外源有机物输入减少，营养化程度降低；④2001～2005年，随着故道环境由开敞武过渡到封闭武，水体的生产力提高，富营养化加剧。初步研究表明，有壳变形虫作为一种环境指示生物在湖泊沉积与生态演化研究中具有重要的应用价值。

Environmental changes in the Swan Oxbow of the Yangtze River in China in the last 3 decades have been documented by morphological diversity, ecological characteristics and assemblages of testate amoebae, combined with pigment data. The study results demonstrate that the regional environment is subjected to the human activities and the channel migration of Yangtze River. The following results were obtained ① during 1975--1987,the water table was low and so many organic matters were input in the region, resulting in the increase of nutritions ; ② in 1987--1994,the water table became high and the water turned clean; ③ in 1994--2001 ,the natural protective region was established in this area, and the input of organic matters decreased, and the nutrition level turned low; and ④ in 2001--2005, when the Swan Oxbow was closed, the process of eutrophication began with growth of aquatic productivity. The research suggests that lacustrine sedimentary testate amoebae, as an excellent indicator of environmental conditions, have valuable implications for environmental changes.