Molecular and biogeochemical evidence for methane cycling beneath the western margin of the Greenland Ice Sheet
Molecular and biogeochemical evidence for methane cycling beneath the western margin of the Greenland Ice Sheet
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DOI：
10.1038/ismej.2014.59
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发表时间：
2014-11-01
期刊：
影响因子：
11
通讯作者：
Christner, Brent C.
中科院分区：
文献类型：
--
作者：
Dieser, Markus;Broemsen, Erik L. J. E.;Christner, Brent C.
在极地冰盖床矿化有机碳并提高溶质产量的微生物过程可能足以影响全球元素循环。为了研究极地冰下微生物生态系统的生物地球化学，我们分析了 2012 年和 2013 年夏季从拉塞尔冰川（位于格陵兰冰盖西缘的陆地终端出口冰川）排出的水。分子数据表明，这些边缘位置的冰下微生物群落中最丰富、最活跃的成分是甲基球菌目细菌（逆转录 (RT)-rRNA 序列的 59-100%）。还检测到来自这些类群的颗粒甲烷单加氧酶 (pmoA) 的 mRNA 转录本，证实甲烷氧化细菌是该冰下生态系统的功能成员。分析的冰下水域中溶解甲烷的范围在2.7至83μM之间，其浓度与溶解氧呈负相关，而与电导率呈正相关。冰下微生物甲烷的产生得到-64%至-62%之间的δC-13-CH4值以及分类为甲烷八叠球菌目和甲烷微生物目的RT-rRNA序列的恢复的支持。在有氧条件下，冰下水中超过 98% 的甲烷在 4 摄氏度左右的培养时间中消耗了 30 天，甲烷氧化速率估计为每天 0.32 μM。我们的研究结果支持格陵兰冰盖该区域下方存在活跃的甲烷循环，其中冰下含氧排水通道中的微生物群落可以作为重要的甲烷汇。
Microbial processes that mineralize organic carbon and enhance solute production at the bed of polar ice sheets could be of a magnitude sufficient to affect global elemental cycles. To investigate the biogeochemistry of a polar subglacial microbial ecosystem, we analyzed water discharged during the summer of 2012 and 2013 from Russell Glacier, a land-terminating outlet glacier at the western margin of the Greenland Ice Sheet. The molecular data implied that the most abundant and active component of the subglacial microbial community at these marginal locations were bacteria within the order Methylococcales (59-100% of reverse transcribed (RT)-rRNA sequences). mRNA transcripts of the particulate methane monooxygenase (pmoA) from these taxa were also detected, confirming that methanotrophic bacteria were functional members of this subglacial ecosystem. Dissolved methane ranged between 2.7 and 83 mu M in the subglacial waters analyzed, and the concentration was inversely correlated with dissolved oxygen while positively correlated with electrical conductivity. Subglacial microbial methane production was supported by delta C-13-CH4 values between -64% and -62% together with the recovery of RT-rRNA sequences that classified within the Methanosarcinales and Methanomicrobiales. Under aerobic conditions, >98% of the methane in the subglacial water was consumed over similar to 30 days incubation at similar to 4 degrees C and rates of methane oxidation were estimated at 0.32 mu M per day. Our results support the occurrence of active methane cycling beneath this region of the Greenland Ice Sheet, where microbial communities poised in oxygenated subglacial drainage channels could serve as significant methane sinks.