While the emissions of methane (CH₄) by natural systems have been widely investigated, CH₄ aquatic sinks are still poorly constrained. Here, we investigated the CH₄ cycle and its interactions with nitrogen (N), iron (Fe) and manganese (Mn) cycles in the oxic-anoxic interface and deep anoxic waters of a small, meromictic and eutrophic lake, during two summertime sampling campaigns. Anaerobic CH₄ oxidation (AOM) was measured from the temporal decrease of CH₄ concentrations, with the addition of three potential electron acceptors (NO₃^–, iron oxides (Fe(OH)₃) and manganese oxides (MnO₂)). Experiments with the addition of either ¹⁵N-labeled nitrate (¹⁵N-NO₃^–) or ¹⁵N-NO₃^– combined with sulfide (H₂S), to measure denitrification, chemolithotrophic denitrification and anaerobic ammonium oxidation (anammox) rates, were also performed. Measurements showed AOM rates up to 3.8 µmol CH₄ L^–1 d^–1 that strongly increased with the addition of NO₃^– and moderately increased with the addition of Fe(OH)₃. No stimulation was observed with MnO₂ added. Potential denitrification and anammox rates up to 63 and 0.27 µmol N₂ L^–1 d^–1, respectively, were measured when only ¹⁵N-NO₃^– was added. When H₂S was added, both denitrification and anammox rates increased. Altogether, these results suggest that prokaryote communities in the redoxcline are able to efficiently use the most available substrates.

中文翻译：

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温带富营养化湖泊中硝酸盐依赖的厌氧甲烷氧化和化学无机营养反硝化作用

虽然自然系统的甲烷 (CH ₄ )排放已得到广泛研究，但 CH ₄水生汇仍然受到很好的限制。在这里，我们研究了 CH ₄循环及其与氮 (N)、铁 (Fe) 和锰 (Mn) 循环的相互作用，在两个夏季采样期间活动。厌氧 CH ₄氧化 (AOM) 是根据 CH ₄浓度随时间的减少测量的，添加了三种潜在的电子受体（NO ₃ ^–、氧化铁 (Fe(OH) ₃）和氧化锰 (MnO ₂₎))。添加¹⁵ N 标记的硝酸盐 ( ¹⁵ N-NO ₃ ^– ) 或¹⁵ N-NO ₃ ^–与硫化物 (H ₂ S) 结合的实验，以测量反硝化、化学无营养反硝化和厌氧氨氧化 (anammox) 速率，也进行了。测量表明AOM速率高达3.8微摩尔CH ₄大号^-1 d ^-1，随着加入的NO强烈增加₃ ^-和适度与添加Fe（OH）的增加₃。MnO ₂没有观察到刺激添加。当仅添加¹⁵ N-NO ₃ ^–时，测得的潜在反硝化和厌氧氨氧化速率分别高达 63 和 0.27 µmol N ₂ L ^–1 d ^–1。当添加H ₂ S 时，反硝化和厌氧氨氧化速率均增加。总之，这些结果表明氧化还原酶中的原核生物群落能够有效地使用最可用的底物。