Iron-Mediated Anaerobic Oxidation of Methane in Brackish Coastal Sediments
Iron-Mediated Anaerobic Oxidation of Methane in Brackish Coastal Sediments
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DOI：
10.1021/es503663z
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发表时间：
2015-01-06
影响因子：
11.4
通讯作者：
Slomp, Caroline P.
中科院分区：
文献类型：
--
作者：
Egger, Matthias;Rasigraf, Olivia;Slomp, Caroline P.
甲烷是一种强大的温室气体，其在海洋沉积物中的生物转化主要受甲烷厌氧氧化（AOM）控制，是全球碳循环的重要组成部分。然而，很少有人知道铁氧化物作为AOM的氧化剂的作用。在这里，我们提供了第一个现场证据，铁依赖AOM在半咸水海岸表层沉积物中，并表明在波的尼亚海沉积物中产生的甲烷被氧化在不同的区域的铁和硫酸盐依赖AOM。在我们的研究现场，近几十年来人为富营养化导致了沉积物中硫酸盐/甲烷过渡区的向上迁移。丰富的铁氧化物和高溶解亚铁表明铁还原的产甲烷沉积物低于新建立的硫酸盐/甲烷过渡。这些沉积物的实验室培养研究强烈表明，在原位微生物群落是能够连接甲烷氧化铁氧化物还原。因此，沿海环境的富营养化可能会创造有利于铁介导的AOM的地球化学条件，从而增加铁依赖的甲烷氧化在未来的相关性。除了在减少甲烷排放方面的作用外，铁依赖的AOM通过还原大量的铁氧化物强烈影响沉积铁循环和相关的地球化学过程。
Methane is a powerful greenhouse gas and its biological conversion in marine sediments, largely controlled by anaerobic oxidation of methane (AOM), is a crucial part of the global carbon cycle. However, little is known about the role of iron oxides as an oxidant for AOM. Here we provide the first field evidence for iron-dependent AOM in brackish coastal surface sediments and show that methane produced in Bothnian Sea sediments is oxidized in distinct zones of iron- and sulfate-dependent AOM. At our study site, anthropogenic eutrophication over recent decades has led to an upward migration of the sulfate/methane transition zone in the sediment. Abundant iron oxides and high dissolved ferrous iron indicate iron reduction in the methanogenic sediments below the newly established sulfate/methane transition. Laboratory incubation studies of these sediments strongly suggest that the in situ microbial community is capable of linking methane oxidation to iron oxide reduction. Eutrophication of coastal environments may therefore create geochemical conditions favorable for iron-mediated AOM and thus increase the relevance of iron-dependent methane oxidation in the future. Besides its role in mitigating methane emissions, iron-dependent AOM strongly impacts sedimentary iron cycling and related biogeochemical processes through the reduction of large quantities of iron oxides.