Food web analyzes in the recent past 100 years

水生生态系统食物网结构的重建是同位素生态学研究的热点。在此背景下，本项目开展了一项开创性的研究，重点是在这五十年中收集的生物鱼类标本。结果总结如下：1)发现用福尔马林固定生物标本会改变肌肉δ ^<13>C，但不会改变相应的δ ^<15>N。2)近50年来贝加尔湖Omul尺度(Coregonus autumn alis migratorius, Georgi) δ ^<13>C明显减少，反映了大气二氧化碳δ ^<13>C的减少。此外，三角洲^<15>N和三角洲^<13>C的时间变化表明了远洋和沿海食物网之间的栖息地变化。3)对琵琶湖Isaza鱼类和沉积物岩心进行了近50年来的研究，重点研究了它们的三角洲^<15>N的变化。近30年来，随着琵琶湖富营养化的发展，Isaza鱼类的三角洲^<15>N和沉积有机质均有所增加。

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.