A century of bottom‐up‐ and top‐down driven changes on a lake planktonic food web: A paleoecological and paleoisotopic study of Lake Annecy, France
A century of bottom‐up‐ and top‐down driven changes on a lake planktonic food web: A paleoecological and paleoisotopic study of Lake Annecy, France
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一个世纪以来，湖泊浮游食物网自下而上和自上而下驱动的变化：法国安纳西湖的古生态和古同位素研究
DOI：
10.4319/lo.2010.55.2.0803
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
J. Reyss
中科院分区：
文献类型：
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作者：
M. Perga;M. Desmet;D. Enters;J. Reyss
我们结合古生态方法和历史监测数据，重建了一个低营养的亚高山湖泊浮游食物网在过去一个世纪的变化。对沉积物中有机质δ15N的分析表明，营养物质的富集始于1910年代，并从1930年代开始加强。沉积物有机碳含量和积累速率、类胡萝卜素浓度、有机质δ13C和枝角类亚化石遗骸的后续变化表明，过量的营养输入引发了湖泊初级生产力和水蚤丰度的自下而上的增加。然而，大型水蚤的大小在20世纪30年代末开始减少，这表明对浮游动物食性白鱼(Coregonus Lavaretus)种群的捕食对大小的选择性增加，这些种群是通过放牧和增加食物供应而培育出来的。白鱼的捕食很可能间接促进了长吻腹鱼的建立。随着营养浓度的降低，水蚤的丰度减少，但它们的大小也减少了，这可能是由于持续的大小选择性捕食。与此同时，博斯米纳的数量翻了一番，这可能是来自较小的水蚤的种间竞争释放的结果。对亚化石枝角类遗骸的δ15N分析表明，枝角类群落结构的这些变化伴随着食物网的重大变化。尽管自20世纪60年代末以来采取了成功的措施来减少营养物质的输入，并减少了初级生产，但每年夏天湖底仍然会发生缺氧。这些模式是由于浮游食物链上自上而下的强烈影响，导致浮游植物衍生的有机物质出口到沉积物中的比例仍然相对较高。
We reconstructed the changes in the planktonic food web of an oligotrophic subalpine lake over the past century, combining paleoecological methods and historical monitoring data. Analyses of organic matter δ15N from sediment cores show that nutrient enrichment started in the 1910s and intensified from the 1930s. Subsequent changes in sediment organic carbon content and accumulation rates, carotenoid pigment concentrations, organic matter δ13C, and cladoceran subfossil remains show that excess nutrient inputs triggered bottom‐up‐driven increases in lake primary production, as well as in Daphnia abundance. Daphnia size, however, started to decrease in the late 1930s, indicating an increasing size‐selective predation from zooplanktivorous whitefish populations (Coregonus lavaretus) that had been fostered by stocking and increased food availability. Whitefish predation is likely to have indirectly facilitated the establishment of Bosmina longirostris. With decreasing nutrient concentrations, Daphnia abundance decreased, but their size declined, presumably due to an ongoing size‐selective predation. At this same time, Bosmina abundance doubled as a likely result of released interspecific competition from smaller Daphnia. δ15N analyses on subfossil cladoceran remains revealed that these changes in cladoceran community structure were accompanied by major changes in the food web. In spite of successful measures to reduce nutrient inputs from the late 1960s and reduced primary production, anoxia still occurs every summer at the lake bottom. These patterns are the consequence of a still relatively high export of phytoplankton‐derived organic matter to the sediment as a result of strong top‐down effects on the planktonic food chain.