应用碳、氮稳定同位素研究鄱阳湖枯水末期水生食物网结构

Food web structure of Poyang Lake during the dry season by stable carbon and nitrogen isotopes analysis

稳定碳、氮同位素比值分析技术是研究生态系统中物质循环与能量流动的有效技术。δ13C值常用来分析消费者食物来源,δ15N值常用来确定生物在食物网中的营养位置。应用稳定同位素技术分析了鄱阳湖北部湖口县、都昌县、星子县、吴城镇4个采样点95条鱼和其他食物网成分样品的碳、氮稳定同位素比值,构建了鄱阳湖枯水期末期水生食物网。结果表明,不同水域颗粒有机物(POM)的δ13C值不同,范围为-27.5‰～-24.6‰可以区分赣江、修水、鄱阳湖、长江和鄱阳湖湖交汇处水体的颗粒有机物特征。江西鄱阳湖国家级自然保护区受人类活动干扰少,核心区生物δ15N相对较低,而周边人类活动频繁的星子、都昌两县附近水域生物体内的δ15N偏高,反映了人类活动引起的营养输入对系统的影响。在湖区不同位置捕获的相同品种水生生物δ13C值不同,反映了其不同的食物来源,用δ15N值计算发现其所占据的相对营养位置较为一致。

Stable isotopes analysis, especially carbon and nitrogen, are now commonly used to study material circulation and energy flow within ecosystems. Carbon isotope ratios （ δ^13C） are used to trace food sources of consumers, while nitrogen isotope ratios （δ^15N） are mainly used to quantify trophic levels of organisms. In this study 95 fish and other food web components from 4 sampling sites： Houkou County, Duchang County, Xingzi County and Wucheng Town, at north Poyang Lake in dry season were used as samples and their stable carbon and nitrogen isotope ratios were analyzed in laboratory. The results of carbon isotopic analyses, ranged from -27.5‰-24.6‰, indicated the δ^13C values of particulate organic matter（POM） could identify different water sources in Ganjiang River, Xiushui River, Poyang Lake and the mixed area of Poyang Lake and Yangtze River. δ^15N values in organisms in the heart of Poyang Lake national nature reserve were lower than those recorded in Xingzi and Duchang counties which were frequently disturbed by human activities i. e anthropogenic sewage increased δ^15N in the ecosystem. The δ^13C values of the same species of aquatic organism varied in different areas of the lake, however their relative trophic levels were similar according to the calculation of δ^15N values.