【作者】 崔莹；

【导师】 吴莹；

【作者基本信息】 华东师范大学 ， 环境工程， 2012， 博士

【摘要】 生态系统的物质流动是生物地球化学循环和生态系统的重要环节,是控制生态系统可持续产出的关键过程。对多重压力下不同类型的生态系统的物质流动进行研究对于实现生态系统可持续产出有重要的现实意义。本文的主要研究内容是分别在中国近海的北部、中部和南部选取特定的研究对象,如在黄海采集了海月水母、沙海蜇和霞水母三种大型水母,在长江口及邻近水域采集了不同洄游阶段的凤鲚,在海南省东部河口区采集了底栖动物和鱼类,分析它们的碳、氮同位素值和脂肪酸组成特征；基于这些生物体的碳、氮同位素和脂肪酸组成特征,运用多元统计分析方法,分别对大型水母、凤鲚、底栖动物和鱼类、虾蟹类的食物组成进行了分析；通过对生物体食物组成的变化特征来反映不同类型食物网的物质传递特征。最后对标志物用于食物网物质传递研究进行总结。首先,同位素和脂肪酸组成对生物体物质来源的表征是成功的。以海南省东部河口生态系统为例,初级生产者红树、海草、大型藻类、浮游植物可以根据碳、氮同位素值和脂肪酸组成进行很好的区分。对这些初级生产者同位素和脂肪酸特征的研究可以为它们在食物网中的传递提供依据。八门湾红树林滩涂底栖食物网中的底栖动物的同位素特征反映了它们对不同碳源、氮源的利用。脂肪酸组成更为细致的反映了它们的食物组成差异,如招潮蟹以潮滩上的底栖微藻为主要食物来源,而对于相手蟹和鼬耳螺,红树生产物的贡献较大,滨螺可能以红树上附着的藻类为食,红树碎屑和水体悬浮颗粒物都是河蚬的食物组成部分,而细菌则是方格星虫的重要食物来源。在黄海,大型水母的同位素特征说明它们的食物基础是海源碳。而较低的18：1n-7/n-9比值和较高的20：1、22：1含量表明这些黄海大型水母是肉食性的,且浮游动物是重要的食物组成。再者,同位素和脂肪酸对生物个体发育过程中的食物组成变化也有很好的识别。典型的研究结果就是对于洄游性鱼类凤鲚在洄游过程中食物组成变化的追踪。洄游过程中的凤鲚(Coilia mystus)δ13C和δ15N值都有所富集,脂肪酸标志物也发生了一定的变化。在洄游过程中,凤鲚体内底栖标志物(18：1n-7,20：4n-6)和浮游标志物(18：1n-9,20：1+22：1)的变化说明：在凤鲚的洄游过程中,底栖食物和浮游食物在不同的洄游阶段交替作为它们的主要食物。索饵期和越冬期的年轻个体以底栖食物(e.g.糠虾)为主要食物来源,肉食性程度相对较差。随着个体的增大,浮游类食物对产卵洄游前期的凤鲚贡献显著提高,桡足类成为主要的食物组成。但是对于处于产卵期的凤鲚,桡足类的贡献又降低,底栖类的食物又有所增加。在与长江口及邻近海域内的浮游动物的时空变化规律对照之后发现,凤鲚的这种食物组成变化与浮游动物的时空变化密切相关。在同一时间和空间尺度下,同位素和脂肪酸也仍然可以很好的表征不同大小的个体之间食物组成差异。如不同体长水母体内的特征脂肪酸变化说明水母在生长过程中很可能发生了食物转换。个体较大的具有较高的20：1+22：1含量,摄食较多的浮游动物,而对于较小的个体,高浓度的15：0+17：0和20：4n-6说明基于碎屑食物链的食物对其贡献更大。而对于多鳞嬉,大于20cm的个体体内20：4n-6的含量和813C、815N值都要高于体长小于20cm(大约10cm左右)的个体。这都反映了多鳞鳝在生长过程中存在从浮游性到底栖性的食物组成变化。基于同位素和脂肪酸组成对不同类型的食物网物质传递途径的研究。凤鲚的滤食性说明它们是浮游食物网的组成部分,对凤鲚的食物组成研究可以反映长江口及邻近水域的浮游食物网物质传递。研究发现浮游食物网的物质传递过程呈现季节和区域变化,与作为浮游食物网基础的浮游生物的群落交替关系密切。而根据底栖生物的食物组成分析,发现红树生产物对红树林底栖食物网的贡献大小依生物种类有差异,外源性的碳如底栖藻类、细菌、浮游生物也是支持红树林底栖食物网的重要碳源。这表明底栖食物网的物质来源非常多样,传递过程互相交叉,非常复杂。而针对这些红树生产物通过底栖食物网向生态系统的高营养级传递情况如何这一问题,对八门湾泻湖食物网中的17种河口性鱼类、虾蟹类的食物组成进行了研究。613C值变化范围较宽,以及生物之间脂肪酸组成的显著差异,都说明这些生物的食物来源比较复杂,食物组成发生分化。紫红笛鲷的低813C、δ15N值可能与它们摄食了以红树生产物为食的生物有关,体内相对较高的18：2n-6含量也证明了这一点。结果表明,红树林向高营养级的传递非常有限(只有极少数种类),而浮游植物、有机碎屑(e.g.底栖藻类)、附着藻类是支持河口生态系统的重要生产者。从食物组成看,凤鲚的食物中既包含了浮游生物,也有底栖生物的存在,而浮游生物对红树林底栖动物也有贡献,多鳞鳝的食物组成更是有从浮游到底栖食物的转变,这都体现了浮游食物网和底栖食物网之间的互相作用。消费者脂肪酸单分子碳同位素值受到食物来源和体内代谢过程的影响,在传递过程中,消费者的脂肪酸δ13C值会变正或者变负,受食物类型和体内分馏过程影响。而且脂肪酸之间变化也呈现差异性,多不饱和脂肪酸的δ13C值保守性相对较强,饱和脂肪酸的δ13C值变化相对较大。δ13C值保守性强的脂肪酸可以很好的反映来源信息。脂肪酸单分子同位素技术在对多因素控制下的生物体的物质来源分析时有一定的优势。更多还原

【Abstract】 Carbon flow within ecosystem, as a key process controlling the sustainable production of the ecosystem, is an important portion in biogeochemical cycle and ecosystem. The research on the carbon flow of various ecosystems under multi-pressure is meaningful to achieve the sustainable production of ecosystems. The major objective of this thesis is to analyze the carbon flow in various ecosystems based on the stable isotope and fatty acid composition of organisms. We collected the specific organisms in north, middle and south of China Sea. For instance, three species macro jellyfishes in the Yellow Sea; Coilia mystus in different migration stages around Changjiang Estuary and adjacent region; benthos and predators in Wenchang/Wenjiao Estuary in eastern Hainan province. Stable carbon and nitrogen isotopes and fatty acid composition of them were analyzed. The diet sources of the organisms were analyzed based on their stable isotopes and fatty acid composition by multivariate analysis. Then the transfer character of various food webs indicated by the diet compositions of organisms was discussed. Finally, the usage of biomarkers in carbon transfer within food web was summarized.Firstly, carbon sources of organisms can be traced by the stable isotopes and fatty acid composition. For example, the producers (i.e. mangrove leaves, seagrass, macroalgae, phytoplankton) in estuarine ecosystem in Wenchang/Wenjiao Estuary can be separated based on the stable isotopes and fatty acid composition, which can provide information for tracing the carbon sources of the food web. The stable isotopes of benthos in Bamen Bay mangrove swamp (δ13C,-24.6%o--12.6%o;δ15N,0.9%o-11.3%o) indicated that the various carbon and nitrogen sources of them. The fatty acid signature of them can reflect the variance in their diet composition. For example, the fiddler crab preyed dominantly on benthic diatom, but for Sesarmidae crab and Cassidula nucleus, mangrove leaves were the dominant diet source. Littorina sp. may forage on epiphyte on the mangrove root and mangrove detritus and suspended particle comprised the diet of bivalve. For Sipunculus nudus, bacteria were important carbon source. For the macro jellyfishes in the Yellow Sea, their stable carbon isotope values indicated that they mainly depended on marine-derived carbon source. Further, the low18:In-7/n-9ratio and high20:1,22:1concentration indicated that they were carnivorous and zooplankton was important diet item of them.Secondly, ontogenetic diet shift experienced by the organisms can also be identified based on the stable isotope and fatty acid composition of them. Taking Coilia mystus as an example, diet changes during their migration were traced using stable isotope and fatty acid composition. Both δ13C and δ15N values were enriched within their migration, with changes in the concentrations of some fatty acid biomarkers. The variation in benthic biomarkers (18:In-7,20:4n-6) and pelagic biomarkers (18:In-9,20:1+22:1) of Coilia mystus indicated that benthic food and pelagic food predominated their diet items alternatively in their various migration stages. Those young individuals in their feeding stages and winter-over stages preyed dominantly on benthic food (e.g. mysidaceas). As their growth, the contribution of pelagic food to larger individuals in their previous spawning stages increased significantly, with copepods as their major diet items. However, the contribution of copepods to those in spawning stages decreased, with that of benthic food increased at the same time. Comparison with the temporal and spatial changes in the zooplankton in Changjiang Estuary and adjacent region revealed that the diet changes of Coilia mystus were closely related to the changes in zooplankton. Even in the same temporal and spatial scales, the diet variation among individuals in various body sizes can also be identified by stable isotope and fatty acid composition. Fro instance, variation in specific fatty acids in jellyfishes of different body sizes suggested that diet shift may happen during their growth. The larger individuals contained high20:1+22:1, preying more zooplankton, but for those smaller ones, the high concentration of15:0+17:0and20:4n-6in their body indicated that the contribution of detritus food chain was bigger. For Sillago sihama, the20:4n-6concentration and δ13C,δ15N vales of the larger individuals (>20cm) all were higher than those of the smaller individuals(<20cm), which suggested that ontogenetic diet shift (from pelagic to more benthic) happened during their growth.Research on the matter transfer routes of various types food webs based on the stable isotopes and fatty acid composition. As filter-feeding species,Coilia mystus was one part of pelagic food web. So the changes in diet composition of them can reflect the character of matter transference within the food web in Changjiang Estuary and adjacent region. The result indicated that the matter transference in the pelagic food web exhibited temporal and spatial variation, and was closely related to the plankton community. As for benthic food web, the diet composition of zoobenthos in mangrove swamp suggested that the contribution of mangrove detritus to the food web was species-dependent, and exogenous carbon (e.g. benthic algae, bacteria, plankton) was also important carbon sources of mangrove benthic food web. The result suggested that the carbon source of benthic food web was multiplex, the transference route was complicated. Diet composition of fishes, shrimps and crabs in BamenBay were analyzed to investigate if the mangrove detritus support the pelagic food web. Wide ranges of δ13C and δ15N values and difference in the fatty acid compositions of the organisms indicated that their diet sources were complicated and they preyed on various items. The lower δ13C and δ15N values of Lutjanus argentimaculatus may due to their feeding on organisms related to the mangrove detritus. The higher18:2n-6concentration in them confirmed the contribution of mangrove detritus. So, it can be concluded that the transference of mangrove detritus to higher trophic level was only limited to specific species. Instead, phytoplankton, benthic diatom and epiphytes were the important nutrient provider in the estuarine ecosystem. Coilia mystus preyed on both pelagic and benthic food, and the plankton also contributed to the diet mangrove zoobenthos. The diet of Sillago sihama even changed from pelagic to benthic food. The interaction between pelagic and benthic food web can be identified from the above research.The δ13C values of fatty acids in predators were influenced by dietary sources and metabolism process. During the transference within food web, the813C values of fatty acids became depleted or enriched, which may be related to diet species and fractionation during metabolism.δ13C values of polyunsaturated fatty acids were consistent, but variation of δ13C values of saturated fatty acids was larger. Fatty acids with persistent613C values in consumers can indicate their dietary sources. The result suggested that stable carbon isotopic ratio of fatty acid had advantage when used as biomarkers to trace the carbon source of organism under various factors.更多还原