Food web analyzes in the recent past 100 years

水生生态系统中食物网结构的重建是当前同位素生态学领域的研究热点。在此背景下，本项目以近50年来采集的生物鱼标本为研究对象，进行了开创性的研究。结果表明：1)福尔马林固定生物标本改变了肌肉增量，但对相应的肌肉增量没有影响；2)50年来从贝加尔湖采集的小鱼(Coregonus auumalisMigratorius，Georgi)的增量明显减少，反映了大气二氧化碳增量的减少。此外，其三角洲和13&GT；C的时间变化表明，OMUL在中上层和沿海食物网之间的栖息地变化。3)研究了碧瓦湖、艾萨鱼和沉积物核心的变化，重点是它们的三角洲和15&GT；N在这50年中的变化。随着琵琶湖富营养化的发展，30年来，伊萨鱼和沉积有机质的增量都在增加。

Reconstruction of food web structure in aquatic ecosystems is the current topics in the field of isotope ecology. In this context, a pioneering study was carried out in this project with emphasis on biological fish specimen collected during these fifty years.Results were summarized as following items.1)The fixation of biological specimen by formalin was found to change muscle delta^<13>C but not for its corresponding delta^<15>N.2)Omul scale(Coregonus autumalis migratorius, Georgi)collected from Lake Baikal during these fifty years exhibited the clear cut decrease in its delta^<13>C reflecting the decrease in delta^<13>C of atmospheric carbon dioxide. Furthermore, temporal variation of its delta^<15>N and delta^<13>C suggested the habitat changes of Omul between the pelagic and coastal food web.3)In Lake Biwa, Isaza fish and sediment core were studied with emphasis on the changes in their delta^<15>N during these fifty years. Both the delta^<15>N of Isaza fish and sedimentary organics increased during last thirty years corresponding to the development of eutrophication in Lake Biwa.