基于Ecopath模型的长江口生态系统营养结构和能量流动研究

Trophic structure and energy flow of the Yangtze Estuary ecosystem based on the analysis with Ecopath model

通过对长江口2016-2017年度4次渔业资源和理化环境的调查数据,运用Ew E(版本6.4.3)软件构建长江口生态系统Ecopath模型,模型功能组包括隐埋性底栖生物、头足类、虾类、蟹类、浮游动物、浮游植物、碎屑等共14个功能组,对该河口生态系统能流分布、营养级聚合分析、能流转化效率及系统发育成熟度等进行研究。结果表明:长江口生态系统各功能组的营养级集中在1~3.93,其中浮游植物与碎屑的营养级为1,浮游动物营养级为2.18,鱼类的营养级分布较广,为2.41~3.93;长江口生态系统能流分布集中在营养级Ⅰ~Ⅲ中,营养级Ⅰ级所占能流比例最高,为53.67%;营养级聚合分析表明,低营养级间的能量转化效率相对较低,而高营养级间的能量转化效率较高。此历史时期长江口生态系统总体能量转化效率为9.3%,表明该河口能量的利用效率未达到最适程度;生态系统总体特征分析显示,该历史时期系统杂食指数和联结指数分别为0.321、0.345,表明长江口生态系统功能组的聚合度较低,食物网结构较为简单,较易受到外界干扰的影响。而生产量/总呼吸量的比值为1.245大于1,表明该河口生态系统趋于不成熟。

Based on the 2016-2017 survey data of fishery resources and eco-environment of the Yangtze Estuary,a mass balance model for the Yangtze Estuary ecosystem was constructed by Ecopath with Ecosim software. The model was composed of 14 functional groups,including benthic producers,cephalopods,shrimps,crabs,upper plankton detritus predators,benthic predators,benthic plankton detritus predators,zooplankton,phytoplankton,detritus,and so on. The result showed： in this ecosystem,the trophic level mainly occurred in the 1-3. 93,and benthic predators have the highest trophic level 3. 93. The Yangtze Estuary＇s energy flow mainly occurred in the first three TLs. Grazing and detritus food chains were the main energy flows in the ecosystem,accounting for the highest proportion,53. 67%. Trophic aggregation analysis showed that the ecosystem was dominated by the grazing food chain. A linear food chain was derived from the mixed trophic network with a mean transfer efficiency of 9. 3%,10. 6% from detritus and 9. 1% from primary producers within the ecosystem. The evaluation of the ecosystem structure and function showed that the connectance index and system omnivory index were 0. 345 and 0. 321; it showed that the function group of this ecosystem had a low degree of polymerization and relatively loose connection,and the food web structure was relatively simple and easy to be affected by external disturbances. And the ratio of total primary production to total respiration was 1. 245 1,showing that the estuary was still immature.