上海青草沙水库食物网结构特征分析

Food Web Structure in Qingcaosha Reservoir of Shanghai, China

为了给青草沙水库生态系统能量流动和物质循环分析提供基础数据,并为生物操纵等生态修复实践提供科学依据,在青草沙水库采集了鱼类、底栖动物、浮游植物、浮游动物和悬浮物样品,结合碳氮稳定同位素(δ^(13)C和δ^(15)N)技术和胃肠内含物分析法,利用IsoSource软件计算了不同食物对消费者的贡献率,并应用"简化食物网"原则,构建青草沙水库生态系统食物网,分析其结构特征。结果显示,青草沙水库食物网的δ^(13)C值为-28.15‰～-21.53‰,δ^(15)N值为6.81‰～14.94‰。在青草沙水库中,刀鲚Coilia nasus和红鳍原鲌Culter erythropterus属于顶级肉食者,其营养级分别3.595和3.589,其他鱼类的营养级在2.482～3.264。青草沙水库食物网结构显示,浮游动物对杂食性鱼类贝氏歺又鱼Hemiculter bleekeri(34%)和寡鳞飘鱼Pseudolaubuca engraulis(32%)的碳源贡献率较高,浮游植物对似鱎Toxabramis swinhonis的贡献率(31%)高于浮游动物(11%),大型无脊椎动物对黄颡鱼Pelteobagrus fulvidraco(60%)和光泽黄颡鱼Pseudobagrus nitidus(64%)的贡献率远高于其他食物成分,处在食物网顶端的刀鲚和红鳍原鲌的食物主要来源于饵料鱼类。青草沙水库食物链长度为3.60个营养级。

Qingcaosha Reservoir was constructed in 2007 to assure drinking water safety for Shanghai City.The reservoir,situated at the Qingcao sandbar of Changxing Island in the Yangtze River estuary,began supplying water in 2010.In this study,the food web of Qingcaosha Reservoir was constructed and its structural characteristics and inter-specific trophic relationships were analyzed by combining stable carbon and nitrogen isotope analysis with gut content analysis.The contribution of potential food sources was calculated using the IsoSource′software package.The study provides fundamental data for analyzing energy flow and matter circulation in Qingcaosha Reservoir and a scientific basis for ecological restoration using bio-manipulation.In August and October 2011,fish,zoobenthos,zooplankton,phytoplankton and seston samples were collected in Qingcaosha Reservoir.Theδ13C values in the food web in Qingcaosha Reservoir ranged from-28.15‰to-21.53‰andδ15N values ranged from 6.81‰to 14.94‰.Coilia nasus and Chanodichthys erythropterus were the two top predators,at trophic levels of 3.595 and 3.589,respectively.The trophic level of other fish species ranged from 2.482 to 3.264.The trophic level of an unidentified Nereididae species was higher than for other benthic macro-invertebrates.Zooplankton provided 34%of the carbon for Hemiculter bleekeri and 32%for Pseudolaubuca engraulis,while phytoplankton contributed a higher proportion(32%)to the food supply of Toxabramis winhonis than did zooplankton(11%).Benthic macroinvertebrates were the primary food source of Tachysurus fulvidraco(64%)and Tachysurus nitidus(60%),while the primary food of C.nasus and C.erythropterus were forage fish.The length of the food chain in Qingcaosha Reservoir was 3.60,shorter than the reported average length(4.0)in lakes,and attributed to the relatively smaller water surface area of Qingcaosha Reservoir and no catch of species from higher trophic levels.Results also indicate that sediments contributed little to the carbon source of benthic macro-invertebrates in Qingcaosha Reservoir,due to the low concentration of organic carbon in sediments.To define dietary compositions more precisely,collection and analysis of food source species should continue,with consumer collection and analysis used as a complementary method.