【作者】 王娜；

【导师】 吴莹；

【作者基本信息】 华东师范大学 ， 海洋化学， 2008， 硕士

【摘要】 本文利用生物标志物脂肪酸分析,结合稳定同位素分析、元素分析,对长江口毗邻海域食物网中主要生物的脂肪酸组成、稳定同位素特征及有机碳氮含量进行研究。建立特定化合物稳定同位素技术（GC/C-IRMS）测定单分子脂肪酸碳稳定同位素的方法,并选取研究海域内采集的部分生物样品,测定其特征脂肪酸的碳同位素比值,从分子水平构建食物网中主要生物的摄食关系。研究生物包括浮游植物、桡足类、水母、箭虫、磷虾类等浮游动物、黄鲫、带鱼、小黄鱼、龙头鱼等海洋鱼类,以及中华管鞭虾、似对虾、褐管蛾螺等底栖动物,总计32种,237个样品。碳氮元素分析采用元素分析仪（Vario ELⅢ）,稳定同位素分析采用稳定同位素质谱仪（Thermo Finnigan Delta plus XP）,脂肪酸分析采用气相色谱仪（Varian CP3800）,单分子脂肪酸稳定同位素分析采用气相色谱-稳定同位素质谱联用（Thermo Finngan气相色谱仪和Thermo Finngan Delt plus XP稳定同位素质谱仪联用）。鱼类肌肉的有机碳含量42.1～55.8%,有机氮含量9.2～15.5%,有机碳、氮含量呈现线性负相关（R²=0.60）,表明长江口毗邻海域鱼类的肌肉中脂肪和蛋白质的比例保持相对稳定。特征脂肪酸能够用于辨别食物网中主要生物的有机质来源,及指示物质在食物网中的传递途径。海洋藻类的脂肪酸标志物二十碳五烯酸（EPA,20∶5n3）和二十二碳六烯酸（DHA,22∶6n3）,随生物种类和生物生长发育期的不同在1～30%波动。在长江口毗邻海域,对于鱼类来说,DHA比EPA具有更高的生物吸收、转化速率,是鱼类生存发育的重要脂肪酸。不同营养级生物体内的多不饱和脂肪酸18∶2n6、18∶3n3、20∶4n6、20∶5n3、22∶5n6、22∶5n3、22∶6n3等存在明显差异。随着营养级的升高,鱼类体内源于浮游植物的16∶1n7和源于浮游动物的22∶1n11不断转化减少,同时多不饱和脂肪酸EPA逐渐增加。性别和生长期是鱼类脂肪酸组成的重要影响因素。11cm是小黄鱼食性发生转变的关键体长,其食性可能由甲壳类、鱼类混合食性转变为鱼类食性为主。以带鱼为例研究发现,随体长增加,雄性带鱼脂肪酸有机碳增加,雌性带鱼脂肪酸有机碳减少。由于母体的贡献,带鱼卵脂肪酸有机碳含量非常高,其中绝大部分是饱和脂肪酸和多不饱和脂肪酸有机碳。将脂肪酸分析结果与主成分分析等聚类分析手段结合,将鱼类划分成不同的食性类群。浮游食性为主的鱼类,主要是中小型中上层鱼类及其他鱼类幼鱼;它们虽然主要以浮游动、植物为食,但所摄食的主要种类又各有偏重。食底栖动物的鱼类,主要是一些底层和近底层鱼类。建立GC/C-IRMS技术测定生物体单分子脂肪酸碳稳定同位素的方法,应用于长江口毗邻海域主要生物种类带鱼、小黄鱼、黄鲫等海洋鱼类,桡足类、箭虫、水母等浮游动物,中国毛虾、周氏新对虾、中华管鞭虾等底栖生物的研究。研究结果表明,东海北部生物的脂肪酸的碳同位素值-19.8～-32.2‰,最低值是浮游植物的22∶6n3,最高值是竹荚鱼的22∶1n11。不饱和度越高,δ¹³C-FA值越低。单分子脂肪酸的碳同位素特征与聚类分析手段结合,能够更准确辨别生产者和消费者之间的捕食关系。水生生物体内普遍存在多不饱和脂肪酸,多不饱和脂肪酸不能通过生物自身合成,而必须从食物中获得,且在消化吸收过程中极少发生结构改变,因此是反映食物来源信息的良好标志物。测定食物来源的某些多不饱和脂肪酸（PUFAs）的稳定碳同位素信息,便可指示食物来源的贡献。更多还原

【Abstract】 In this thesis,previous marine food web studies,including gut content analysis,carbon and nitrogen stable isotope analysis,fatty acid components analysis,were reviewed in detail.A new method detecting carbon stable isotope of individual fatty acid was constructed and evaluated.Habitual organisms in north of East China Sea and alongshore estuarine water areas were measured by different methods mentioned above in order to understand the role of diverse aquatic species composing specific food webs and their control on the flow of matter and energy along the food chain.Trophic member phytoplankton,zooplankton,primary fish species and bottom-dwelling species were analyzed.Carbon and nitrogen was analyzed by Elemental Analyzer （Vario ELⅢ）,carbon and nitrogen stable isotope ratios were determined on isotope ratio mass spectrum（IRMS,Thermo Finnigan Delta plus XP）,fatty acids were measured by use of Gas Chromatography instrument（GC,Varian CP3800）,and carbon stable isotopes of individual fatty acids were tested by combination of Thermo Finngan GC and Thermo Finngan Delt plus XP IRMS.Organic carbon content of fish dorsal muscle varied from 42.11%to 55.8% and nitrogen contnent from 9.19%to 15.52%.The negative linear correlation between organic carbon and nitrogen（R²=0.602）indicated that there existed a relative balance of the ration of lipid and protein in the muscle.The fatty acids pattern or specific biomarker fatty acids of consumers were proved to be effective to identify food sources.Nevertheless,the specific marker eicosapentaenoic acid（EPA,20:5n3）and docosahexaenoic acid（DHA, 22:6n3）for marine algae food source structure fluctuated from 1%to 30%of all fatty acids among species and individuals.Also,DHA has a higher adsorption and assimilation efficiency than that of EPA,thus playing a crucial role for the survival and growth of fish.Seven highly unsaturated fatty acids（PUFA）,i.e., 18:2n6、18:3n3、20:4n6、20:5n3、22:5n6、22:5n3、and 22:6n3,change a lot among species in different communities in the north of East Cina Sea.In fish musucle,with trophic level increase,fatty acid 16:1n7 for phytoplankton decreased,while fatty acid 18:1n7 for zooplankton increased.Gender and life stage are critical factors influencing the fatty acid composition of fish species.Total length 11cm is a turning point for Larimichthyspolyactis,whose food habits transformed from crustacean and fish to fish dominant.For Trichiurusjaponicus species with total length increasing,organic carbon of fatty acids increased in male individuals while decreased in female.Spawn had a large amount of organic carbon of fatty acids relatively,wherein unsaturated fatty acid contributed the most.Combined fatty acid content analysis with Cluster and ADS analyses,fish species were separated into two groups.Fish feed on plankton were most pelagic species and larva with specific prey preference,respectively.Benthos feeders were bottom-dwelling or demersal species.Thrissakarnrnalensis was the basal pelagic phytoplankton feeder,while Trachurus japouicu was commonly feed in seagrass circumstance.GC/C-IRMS analysis was applied to fish,zooplankton and demersal species. The results showed thatδ¹³C varied from -19.8 to -32.2‰,of which the minimum one was 22:6n3 for phytoplankton and the maximum 22:1n11 for Trachurus japouicus.Generally,¹³C/¹²C ratio was less negative in saturated fatty acids.With desaturation increases,δ¹³C-FA values decline.It is further demonstrated that ¹³C/¹²C ratios of individual fatty acids in potential prey（diet） and consumers allow identifying carbon fluxes and trophic links.Highly unsaturated fatty acids（PUFAs）are often used as dietary indicators since they cannot be created de novo,are seldom modified by marine organisms due to biochemical limitations,and are typically the most common fatty acids in marine ecosystems.更多还原