基于Ecopath模型的太湖生态系统结构与功能分析

根据2008—2009年太湖湖区水生生物调查的结果及主要水生动物摄食生态学已发表资料，应用Ecopath with Ecosim 6.1软件构建了太湖生态系统的食物网模型，初步分析了太湖生态系统功能与结构特征.模型由初级生产者、主要鱼类及无脊椎动物和有机碎屑等20个功能组组成.结果表明： 太湖生态系统的能流主要分布在4个营养级上，顶级捕食者鲌鱼营养级最高.食物网存在两条主要的营养传递途径，即碎屑食物链和牧食食物链，且碎屑食物链占比较大；营养级I的利用效率低下，大量初级生产力未能流入更高的营养层次，造成生态系统下层的营养流动“阻塞”.对系统总体特征分析发现，反映系统成熟度的指标，包括较高的净初级生产力(NPP)和净初级生产力/呼吸(NPP/R)，以及较低的连接指数(CI)、系统杂食指数(SOI)和Finn循环指数(FCI)等，都揭示了太湖“幼态化”的生态系统现状；混合营养分析和关键种筛选结果显示，高强度的渔业捕捞活动对系统负影响显著，而顶级捕食者的下行效应显著下降.

Analysis on the ecosystem structure and function of Lake Taihu based on Ecopath model.

Based on the data of lake survey conducted during 2008-2009 and the published data of the trophic ecology of key species, the exploited freshwater ecosystem of Lake Taihu was described using Ecopath with Ecosim 6.1 with the aim of characterizing its functioning and structure. The model comprised 20 functional groups including primary producers, the main species of fishes, non fish vertebrates, and detritus. Results showed that the functional groups were organized into four aggregated trophic levels with the highest levels corresponding to the top predators, culters. Two trophic pathways were found in Lake Taihu, the detrital pathway and grazing pathway. The detrital pathway dominated in the ecosystem. As a consequence of the low ecotrophic efficiency of primary producer and detritus (trophic level Ⅰ), the accumulating detrital sediments continually released waste nutrients back into the system, resulting in its internal pollution. Considering Odum and Ulanowicz’s theory of ecosystem development, the ecosystem was placed on a low developmental stage with high net primary production (NPP), net primary production/total respiration (NPP/R) and lower connectance index (CI), system omnivory index (SOI), and Finn’s cycling index (FCI). The results of mixed trophic impacts and keystone species selection showed that the increasingly intensive fishing exerted a negative effect on the ecosystem, and the top down effects of top predators were becoming much obviously reduced.