根据近30年来的长江口大型底栖动物群落的历史资料,以及2009年和2010年的现场调查数据,从长江口底栖动物群落结构变化特征出发,分析了其长期演变的过程和规律,旨在阐明底栖动物群落的演变趋势,识别其重要演变时段.同时结合长江口海域近50～60年来的入海径流量和携沙量变化、营养盐和DO等水质特征变化,分析底栖动物群落的变化原因.分析结果表明,长江口底栖生物群落的变化可大体分为3个阶段,第一阶段是20世纪90年代之前,底栖生物群落无论物种数、生物量都维持相对较高的水平；第二阶段发生在20世纪90年代初至2005年,由于受到气候变化和人类活动的综合影响,底栖生物群落的上述指标都有所降低,表明受到自然和人为因素干扰的加剧；第三阶段是2005年之后至现在,由于长江口水域的各项生态环境保护措施加强,底栖生物群落得到一定程度的恢复.通过对长江口海域各种环境因素的分析表明,底栖生物群落变化受到长江口区域生物因素和非生物因素的共同影响,变化趋势也与环境因素的变化比较吻合.%The macrobenthos samples collected from Changjiang Estuary, China in 2009 and 2010 were i-dentified to clarify the current state, and the historical data obtained from essentially the same sampling area were analyzed to get the long-term trends and their response to environmental changes over the past 30 years. The average total species number exhibited an obvious fluctuation over this 30 year period, which includes three periods, e. g. , period one-before 1990s, the total species number maintained relatively high value, period two-from 1990s to 2005, the total species number decreased markedly, and period three-after 2005, the total species number increased rapidly. The average biomass and the abundance also had similar trends over the last 30 years. The trends of species composition of macrobenthos community was that some long-lived, larger sized, stress intolerant resident species had been replaced by some opportunistic, shortlived, small sized taxa, especially some opportunistic polychaeta species, which indicated the macrobenthos community of the study area was unhealthy and unstable. The results of MDS ordination also approximately coincide with the above results. The integrated impacts both from climate changes and from anthropogenic disturbances, such as aquaculture, coastal land reclamation and sewage discharge were the triggers for these long-term changes.
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