Both the frequency and intensity of drought events are expected to increase, with unresolved alterations to peatland methane cycling and the involved microbial communities. While existing studies have assessed drought effects via experimental approaches under controlled conditions, to our knowledge, no studies have examined the in-situ effects of natural drought in restored temperate fens. In this study, we used quantitative polymerase chain reaction (qPCR) and high throughput 16S rRNA gene amplicon sequencing of DNA and complementary DNA (cDNA) to determine the abundances and community structure of total and putatively active microbial communities following the 2018 European summer drought. Together with geochemical and methane flux data, we compared these results to a non-drought reference dataset. During drought, water level and methane flux rates decreased to a new recent minimum in both fens. This corresponded with pronounced shifts in porewater geochemistry. Microbial community composition in the drought year differed markedly, and was characterized by a greater relative and total abundance of aerobic methanotrophs, and, in one of the two sites, by a decrease in total methanogen abundance. In contrast to the non-drought reference years, type I methanotrophs were clearly more dominant than type II methanotrophs in both fens. cDNA sequencing confirmed the activity of type I methanotrophs during drought, with Methylomonaceae having the highest average relative abundance of bacterial cDNA transcripts. We show that changes in microbial community dynamics, porewater geochemistry, and ecosystem methane fluxes can be substantial following natural drought in restored fens, and provide the first in-situ evidence from a natural drought which suggests type I methanotroph populations are more active than type II methanotrophs in response to drought effects. Type I methanotrophs may represent a key microbial control over methane emissions in restored temperate fens subject to natural drought.

预计干旱事件的频率和强度都会增加，泥炭地甲烷循环和相关微生物群落的变化尚未解决。虽然现有的研究已经在受控条件下通过实验方法评估了干旱影响，但据我们所知，没有研究检查过原位自然干旱对恢复温带沼泽的影响。在这项研究中，我们使用定量聚合酶链反应 (qPCR) 和 DNA 和互补 DNA (cDNA) 的高通量 16S rRNA 基因扩增子测序来确定 2018 年欧洲夏季干旱后总的和假定活跃的微生物群落的丰度和群落结构。连同地球化学和甲烷通量数据，我们将这些结果与非干旱参考数据集进行了比较。在干旱期间，两个沼泽地的水位和甲烷通量率均降至最近的最低值。这与孔隙水地球化学的显着变化相对应。干旱年份的微生物群落组成存在显着差异，其特征是好氧甲烷氧化菌的相对丰度和总丰度更高，并且，在两个地点之一，通过总产甲烷菌丰度的减少。与非干旱参考年份相比，在两个沼泽中，I 型甲烷氧化菌明显比 II 型甲烷氧化菌更具优势。cDNA 测序证实了干旱期间 I 型甲烷氧化菌的活性，其中具有最高平均相对丰度的细菌 cDNA 转录本的甲基单胞菌科。我们表明，在恢复的沼泽地自然干旱后，微生物群落动态、孔隙水地球化学和生态系统甲烷通量的变化可能很大，并提供了来自自然干旱的第一个原位证据，这表明 I 型甲烷氧化菌种群比 II 型更活跃甲烷氧化菌对干旱影响的反应。I型甲烷氧化菌可能代表了受自然干旱影响的恢复温带沼泽中甲烷排放的关键微生物控制。