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题名: 基于生态通道模型的长江口水域生态系统模拟研究
作者: 韩瑞
学位类别: 博士后
答辩日期: 2015-12
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 杨敏 ; 陈求稳
关键词: 长江口水域 ; Yangtze River estuary and adjacent seas ; 生态系统结构 ; ecosystem structure ; 能量流动 ; energy flow ; 生态通道模型 ; Ecopath model
其他题名: The simulation of Yangtze River estuary and adjacemt coastal ecosystem basing on Ecopath model
学位专业: 环境工程
中文摘要:       河口生态系统是河流生态系统和海洋生态系统之间的生态交错带,其多样的生态功能及复杂的能量流动过程决定了河口错综复杂的生物组成和特殊的生态功能定位。因此,研究河口生态系统对人为干扰(包括大型水利工程、河口整治开发等)的响应机制具有重要意义。长江口是我国极为重要的生态交错区,区内理化环境因子复杂多变,生物群落的生态类型多样,生态系统具有生产力水平高、环境梯度变化大等特点。同时,长江流域内水利工程众多,其运行对长江口生态系统的叠加效应不容小觑。尤其在三峡工程运行后,变化的长江口水域化学/水沙组成通过生态阀门反馈或叠加作用,影响长江口生物群落的分布乃至生态系统的发展。
      本研究利用生态通道模型(Ecopath with Ecosim模型)在前期研究的基础上构建了三个时期(三峡蓄水前期-2000年、三峡蓄水中期-2006年、三峡蓄水后期-2012年)长江口水域生态系统模型,分析对比了三峡工程蓄水前中后期,长江口水域生态系统营养结构与能量流动的特征。模型将长江口水域生态系统划分为鱼类、虾类、蟹类、头足类、底栖动物、浮游动物、浮游植物、碎屑等17个功能组,基本覆盖了长江口水域生态系统能量流动的主要途径。模型计算了不同时期长江口水域生态系统的重要特征参数,量化了长江口生态系统结构、功能及能量流动等,得出的主要结论如下:
① 三峡工程蓄水前、中、后期,长江口水域生态系统中各功能组的营养级组成和分布相近,但蓄水后功能组生态营养转换率普遍提高,这可能是由于长江口面临的捕捞压力逐年增加,较高营养层次转换成终极产品的转换率被动提高;
② 长江口水域渔获物结构在不同时期变化不明显,但渔获物的平均营养级降低,渔获量也有所减少,渔业资源呈现小型化、低值化的趋势。近年来,由于长江流域经济的迅速发展,大量污染物随径流至河口,不断加重河口污染,导致水域富营养化日趋严重,这可能是渔业资源变化的原因之一;
③ 三峡工程蓄水后,长江入海径流量减少约18%,长江冲淡水面积缩减,陆源营养物质和悬浮颗粒的输入减少,海水透明度升高,促进了藻类等浮游生物的生长,使得长江口水域生态系统中的能量传递更依赖牧食食物链,造成大部分剩余能量在生态系统中沉积,增大生态系统内源性污染的风险;
④ 长江口水域生态系统在三峡蓄水前、中、后期均处于不成熟阶段,蓄水后生态系统的总能流量、总生产量、初级生产量及流向碎屑的能量均有所降低,但系统的净效率和再循环率升高,能量在生态系统中流动的路径增多、营养交互关系变得更为复杂,对外界扰动的适应性有所增强。
英文摘要:        Estuarine ecosystem is the ecotone of river ecosystem and marine ecosystem, whose complicated process of ecological functions and energy flows can determine the variable biotic components and the special position of ecological functions. Therefore, to study the responding mechanism of estuarine ecosystem to artificial disturbance (including large water projects, estuary regulation and exploitation) is extremely significant. Yangtze River estuary is a very critical ecotone in China, the physicochemical environmental factors of this zone varies a lot, the ecological types of bio-community has a great diversity, the level of productive forces is relatively high and the environmental gradients has changed obviously. Meanwhile, the cumulative impacts of water conservancy projects in the Yangtze River basin, especially the Three Gorges Reservoir, have had a significant effect on the biological and ecological integrity of the Yangtze River estuarine ecosystem.
      During this research, we establishes three ecopath models of the Yangtze River estuary and adjacent seas before (the year of 2000), during (the year of 2006), and after (the year of 2012) the impoundments of the Three Gorges Reservoir, using Ecopath and Ecosim software to characterize and compare the estuarine ecosystem’s food web structure and energy flow. Sensitivity analyses were carried out to evaluate the uncertainty levels of the models. The three models consisted of 17 functional groups covering the main paths of the ecosystem food web, including piscivorous fishes, generalist predators, shrimp predators, zooplanktivores, crab predators, other pelagic fishes, other demersal fishes, other benthic fishes, shrimp, crabs, jellyfish, cephalopods, macrobenthos, meiobenthos, zooplankton, phytoplankton, and detritus.
      The simulated results showed that the values of trophic levels (TL) ranged from 1.000 to 3.802 in 2000 (before the impoundments), from 1.000 to 4.058 in 2006 (during the impoundments), and from 1.000 to 4.019 in 2012 (after the impoundments). This indicates that the TLs distributions of the functional groups were similar under all three conditions. However, the ecotrophic efficiencies of commercial species, such as Pseudosciaena polyactis, were elevated because of the increased fishing intensity in the Yangtze River estuary. The structure of catches did not change noticeably during this period, but the mean trophic level of the catch decreased from 3.406 to 3.369, as did the number of catches (from 1.026 t/km2/year to 0.719 t/km2/year). Meanwhile, after the impoundments the role of the detritus food chain became less important to the energy transfer process than that of the grazing food chain, and over 90% of the energy flows were assembled in TL I and II, most of which flow into detritus and could be a source of internal pollution. The total transfer efficiency of the Yangtze River estuary ecosystem was 10.2% in 2000, 10.0% in 2006 and 9.4% in 2012. All of these negative effects are likely to be closely related to reductions in freshwater and sediment discharges, as well as the increase of land-based pollution in the Yangtze River Basin. Furthermore, the result also showed that the parameters of total biomass, total primary production, and the sum of all flows into detritus gradually decreased;  however, the gross efficiency, Finn cycling index, Finn’s mean path length, and system omnivory index increased. The ecosystems (before, during, and after impoundments) were found to remain in the immature stage.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/36800
Appears in Collections:环境水质学国家重点实验室_学位论文

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Recommended Citation:
韩瑞. 基于生态通道模型的长江口水域生态系统模拟研究[D]. 北京. 中国科学院研究生院. 2015.
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