Formation of diatom frustules depends on the process of silicification. In many planktonic species of algae, ambient temperature and nutrients are already known to affect growth and morphology, making them suitable bioindicators. In this study, a similar indicator function of benthic diatoms is proposed based on the principle that cell wall thickness is inversely proportional to temperature and nutrients. Therefore, higher turnover rates at warmer temperatures are hypothesized to favour smaller and lighter diatoms due to their shorter regeneration time. Accordingly, benthic diatom species were classified into seven categories according to their intensity of silicification, referred to as ‘Silicification Value’. For each diatom assemblage, an abundance-weighted average silicification value was calculated and tested for its applicability to assess global change impact on mountain lakes in the northern calcareous Alps of Europe. Surface sediment diatom samples and morphometric and ecological parameters of 41 lakes from a wide altitudinal range in the Bavarian and Tyrolian Alps were collected and analysed. Statistical tests revealed that temperature conditions in a lake and its altitude were the most decisive proxies related to the ‘Silicification Value’. Moreover, trophic status and the presence of macrophytes had some influence. This supported the hypothesis that lakes, which are warmer and richer in nutrients, show a weaker average silicification in diatom assemblages. A dependence of silicification on valve size could be shown but appears to be negligible in climatological issues. In particular, the correlation with temperature makes the silicification value an applicable palaeoecological proxy to assess climate change impact in freshwater lakes.

中文翻译：

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硅化值：一种新的基于硅藻的指标，用于评估淡水栖息地的气候变化

硅藻壳的形成取决于硅化过程。在许多浮游藻类中，已知环境温度和营养物质会影响生长和形态，使其成为合适的生物指标。本研究基于细胞壁厚度与温度和养分成反比的原理，提出了类似的底栖硅藻指示剂功能。因此，假设在较高温度下较高的周转率有利于较小和较轻的硅藻，因为它们的再生时间较短。因此，底栖硅藻物种根据其硅化强度分为七类，称为“硅化值”。对于每个硅藻组合，计算了丰度加权平均硅化值，并测试了其在评估全球变化对欧洲北部石灰质阿尔卑斯山高山湖泊的影响的适用性。收集并分析了来自巴伐利亚和蒂罗尔阿尔卑斯山脉的广泛海拔范围的 41 个湖泊的表层沉积硅藻样品以及形态测量和生态参数。统计测试表明，湖泊的温度条件及其海拔高度是与“硅化值”相关的最具决定性的指标。此外，营养状况和大型植物的存在也有一些影响。这支持了一个假设，即温度更高、营养更丰富的湖泊在硅藻组合中表现出较弱的平均硅化作用。可以显示硅化对阀门尺寸的依赖性，但在气候问题中似乎可以忽略不计。