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Dynamics of pelagic diatoms in Lake Geneva from 1974 to 2007

机译：1974年至2007年日内瓦湖上层硅藻的动态

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Phytoplankton in Lake Geneva was sampled each month from 7974 to 7980 and two times a month from 1981 to 2007. Water samples were collected in the upper layer (0-10 m until end of 2001, and 0-20 in after 2001) using an integral sampler (Pelletier et Orand, 1978). After lugol fixation and sedimentation in Utermohl chambers, the organisms were identified and counted using an? inverted ZEISS microscope. Relative abundance of diatoms in phytoplankton showed large variations (from 0.1% to 91% of phytoplankton biomass) depending on the season and the year. Most abundant taxa were Asterionella formosa, Fragilaria crotonensis and Ulnaria ulna f. angustissima found respectively in 88%, 83% and 66% of the samples. Stephanodiscus minutulus, with 62% presence was very abundant from 1974 to 1980, and decreased after Diatoma tenuis was the diatom which showed the highest biomass (11,6 mg/L-1, august 9, 2001) along the entire studied period. Compared to the other algal classes, Mougeotia gracillima (colonial Zygophyceae) reached 39,0 mg/L-1 on July 25 2007. Nine diatom taxa reached a biomass over 1 mg/L-1 124 diatom taxa were identified during the studied period, compared to 538 diatom taxa already recorded in the lake from 1852 to nowadays (Druart and Balvay 2007). Dynamic of the most abundant taxa are compared. Art artificial neural networks analysis was used, an emergent self organizing map was computed. 8 diatom communities (groups of sampling sites) were identified with this analysis. Some of these communities are characteristic of cold seasons, other of warm seasons. Inter-annual dynamics of the communities can be related to the re-oligotrophication of the Like.
机译：每月从7974至7980对日内瓦湖的浮游植物进行采样，从1981至2007年每月进行两次采样。在上层（直到2001年底为0-10 m，从2001年之后为0-20）收集水样，积分采样器（Pelletier et Orand，1978）。在将Lugol固定并沉淀在Utermohl箱中后，对微生物进行了鉴定和计数。倒置蔡司显微镜。浮游植物中硅藻的相对丰度显示出很大的变化（从浮游植物生物量的0.1％到91％），具体取决于季节和年份。最丰富的分类群是福寿螺，克雷格罗尼亚草和尺骨尺木。分别在88％，83％和66％的样本中发现了angustissima。 1974年至1980年间，细粉金线菊的存在非常丰富，从1974年到1980年非常丰富，而在整个研究期间，硅藻（Diatoma tenuis）是显示最高生物量（11,6 mg / L-1，2001年8月9日）的硅藻之后，其含量下降。与其他藻类相比，到2007年7月25日，草茂木（殖民地Zygophyceae）达到39,0 mg / L-1。在研究期间，确定了九个硅藻类群的生物量超过1 mg / L-1 124硅藻类群，相比之下，从1852年至今，湖泊中已经记录了538个硅藻类群（Druart和Balvay 2007）。比较最丰富的分类单元的动态。使用了人工神经网络分析技术，计算了紧急的自组织图。这项分析确定了8个硅藻群落（采样点组）。这些社区中有些是寒冷季节的特征，而其他则是温暖季节的特征。社区的年际动态可能与Like的重新寡营养化有关。

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