Abstract Methane (CH4) is an important atmospheric trace gas mostly released from wet anoxic soils and sediments. While many studies have focused on relatively homogenous environments like rice fields and lake sediments, the changing contribution of heterogeneous sediments e.g. along the longitudinal profile of a rivers has not been covered very frequently. Here we investigated sediment samples from 11 locations of the Elbe River. Sediments were incubated to measure methanogenic/methanotrophic potentials and contribution of individual methanogenic pathways using isotope analysis of δ13C. Additionally, we determined the diversity of the methanogenic communities (analysis of T-RFLP targeting the mcr-A gene in the sediment samples), while abundances of archaea, methanogens and methanotrophs were determined by qPCR. The CH4 production was detected in six samples (out of 11 examined) and ranged from 0.12 to 644.72 nmol gDW−1 d−1. Methanotrophy was found in all examined sediment samples and ranged from 654 to 10,875 nmol gDW−1 d−1. Abundance of methanogens and methanotrophs (Mcr-A and pmo-A gene copy numbers) was not significantly different and quite stable around 106 to 107 copies gDW−1. The group specific qPCR showed high fluctuations, while the highest counts were reported for Methanomicrobiales and Methanosarcinales (105 to 108 copies per gram dry sediment), followed by Methanobacteriales (103 to 105 copies per gram dry sediment). A significant proportion of unidentified methanogens was found in almost every locality. Isotope analysis of δ13C showed that (CH4) is produced mainly by hydrogenotrophic methanogens. We see no trend in the studied parameters along the Elbe River. The molecular data showed no spatial characteristics, while we found hotspots of the measured CH4 processes (CH4 production and oxidation) due to other local driving factors (e.g. carbon content). Thus, out results indicate that the observed variability of the CH4 production and oxidation rates is only indirectly linked to the presence or quantities of different microbial guilds.

中文翻译：

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易北河沿岸沉积物甲烷动态

摘要 甲烷（CH4）是一种重要的大气痕量气体，主要从潮湿的缺氧土壤和沉积物中释放出来。虽然许多研究都集中在相对同质的环境，如稻田和湖泊沉积物，但异质沉积物的变化贡献，例如沿河流的纵向剖面，并未经常涉及。在这里，我们调查了易北河 11 个地点的沉积物样本。培养沉积物以使用 δ13C 的同位素分析测量产甲烷/甲烷氧化潜力和各个产甲烷途径的贡献。此外，我们确定了产甲烷菌群落的多样性（分析了沉积物样品中针对 mcr-A 基因的 T-RFLP），而通过 qPCR 确定了古细菌、产甲烷菌和甲烷氧化菌的丰度。在 6 个样品中检测到 CH4 产生（在检查的 11 个样品中），范围从 0.12 到 644.72 nmol gDW-1 d-1。在所有检查的沉积物样品中都发现了甲烷营养，范围从 654 到 10,875 nmol gDW-1 d-1。产甲烷菌和甲烷氧化菌（Mcr-A 和 pmo-A 基因拷贝数）的丰度没有显着差异，并且在 gDW-1 的 106 到 107 个拷贝左右相当稳定。组特异性 qPCR 显示出高波动，而甲烷微生物和甲烷八叠球菌的计数最高（每克干沉积物 105 至 108 拷贝），其次是甲烷杆菌（每克干沉积物 103 至 105 拷贝）。几乎每个地方都发现了很大比例的不明产甲烷菌。δ13​​C 的同位素分析表明 (CH4) 主要由氢营养型产甲烷菌产生。我们在易北河沿岸的研究参数中没有看到任何趋势。分子数据没有显示空间特征，而我们发现了由于其他局部驱动因素（例如碳含量）导致的测量 CH4 过程（CH4 产生和氧化）的热点。因此，out 结果表明观察到的 CH4 生产和氧化速率的可变性仅与不同微生物群的存在或数量间接相关。