杭州湾北岸大型围隔海域人工生态系统的能量流动和网络分析

Energy flux and network analysis for an artificial ecosystem of a large enclosed sea area in North Hangzhou Bay

根据2006年在杭州湾北岸大型围隔海域进行的生态调查数据,利用EwE软件构建围隔海域人工生态系统的能量流动模型。模型由13个功能组构成,分别是肉食性鱼类、底栖捕食鱼类、浮游动物性鱼类、草食性鱼类、蟹类、虾类、软体动物、底栖动物、肉食性浮游动物、植食性浮游动物、大型藻类、浮游植物和有机碎屑,每一组都代表在生态系统中具有相似地位的有机体,基本覆盖了该人工生态系统能量流动的主要过程。能量流动分析表明,围隔海域人工生态系统中能量流动主要以碎屑食物链途径为主,其中植食性浮游动物在能量从低级向高层次转换中起关键作用。人工生态系统的营养级范围为1.00～3.90级,系统的能量流动主要有6级,来自初级生产者的能流效率为9.4%,来自碎屑的转换效率为9.8%,平均能量转换效率为9.6%。经生态网络分析,直接来源于碎屑的比例占总流量的57%,而直接来源于初级生产者的比例为43%,生态系统特征参数:总初级生产计算量/总呼吸量(TPP/TR)、系统物质和能量循环率(FCI)和系统聚合度(A)值分别为2.672、0.25、0.315,表明围隔海域人工生态系统目前正处于发育时期。该研究为首次利用Ecopath模型分析大型围隔海域人工生态系统的结构和能量流动,旨在为富营养化近岸海域的生态修复提供理论依据。

Using the Ecopath with Ecosim software, we constructed atrophic structure model of a large enclosed sea area in north Hangzhou Bay to analyze the main biomass flows in the artificial ecosystem. The structure model is based mostly on the 2006 survey data and it provides a snapshot of how the artificial ecosystem operates. The model consists of 13 functional groups, which are piseivorous fish, benthic-feeding fish, zooplanktivorous fish, herbivorous fish, crabs, shrimp, mollusea, infauna, carnivorous zooplankton, herbivorous zooplankton, periphyton, phytoplankton and detritus. Each group represents organisms with a similar role in the food web, and the 13 functional groups cover the main trophic flow in the artificial ecosystem. The results show that the food web in a large enclosed sea area is dominated by the detrital path, and herbivorous zooplankton plays a significant role in transferring energy from detritus to higher trophic levels. Trophic levels of the compartments vary from 1.00 for the primary producers and detritus to 3.90 for the piscivorous fish. Through network analysis, the system network is mapped into a linear food chain and six discrete trophic levels are found with a mean transfer efficiency of 9.8% from detritus and 9.4% from ihe primary producers within the ecosystem. The geometric mean of the trophic transfer efficiencies is 9.6%. In the course of energy flow, the proportion of total flow originating from detritus is 57% , and that from the primary producers is 43%. Three indexes of ecosystem maturity, TPP/TR, FCI and Ascendancy, are 2.672, 0.25 and 0. 315 respectively, indicating that the artificial ecosystem of a large enclosed sea area in north Hangzhou Bay is in the state of development. This is the first reported trophic model of a large artificially enclosed sea area; it may serve as the basis for future bioremediation and ecosystem management in eutrophic coastal sea areas.