Microbial decomposition of marine dissolved organic matter in cool oceanic crust
Microbial decomposition of marine dissolved organic matter in cool oceanic crust
复制标题
DOI：
10.1038/s41561-018-0109-5
复制
发表时间：
2018-05
影响因子：
18.3
通讯作者：
Sunita R. Shah Walter;U. Jaekel;Helena Osterholz;A. Fisher;J. Huber;A. Pearson;T. Dittmar;P. Girguis-P.
中科院分区：
文献类型：
--
作者：
Sunita R. Shah Walter;U. Jaekel;Helena Osterholz;A. Fisher;J. Huber;A. Pearson;T. Dittmar;P. Girguis-P.
海洋溶解有机碳(DOC)是地球上最大的活性还原碳储存库之一。在深海中，DOC一直被描述为生物顽固性，其放射性碳年龄为4,000至6,000 年，远远超过海洋倾覆的时间尺度。然而，非生物去除机制不能解释深海DOC损失的全部规模。深海水在低温下通过海脊两侧的火山壳循环，但人们对相关的生物地球化学过程和碳循环知之甚少。本文分析了安装在大西洋中脊以西地壳岩石中的两个钻孔的流体中的DOC，并表明深海DOC从这些冷却的循环流体中被去除了。去除机制是同位素选择性的，并导致分子组成的特定特征发生变化，与微生物介导的氧化一致。我们认为，平均放射性碳龄为3,200 年的有机分子对地壳微生物是可生物利用的，这种去除机制可能至少占全球深海DOC损失的5%。寒冷的地壳环流可能通过将残留的有机碳成分排放到深海中，将14C和13C分子降解和耗尽的有机碳成分排放到深海中，从而维持深海作为老化的和难降解的DOC的储存库。
Marine dissolved organic carbon (DOC) is one of the largest active reservoirs of reduced carbon on Earth. In the deep ocean, DOC has been described as biologically recalcitrant and has a radiocarbon age of 4,000 to 6,000 years, which far exceeds the timescale of ocean overturning. However, abiotic removal mechanisms cannot account for the full magnitude of deep-ocean DOC loss. Deep-ocean water circulates at low temperatures through volcanic crust on ridge flanks, but little is known about the associated biogeochemical processes and carbon cycling. Here we present analyses of DOC in fluids from two borehole observatories installed in crustal rocks west of the Mid-Atlantic Ridge, and show that deep-ocean DOC is removed from these cool circulating fluids. The removal mechanism is isotopically selective and causes a shift in specific features of molecular composition, consistent with microbe-mediated oxidation. We suggest organic molecules with an average radiocarbon age of 3,200 years are bioavailable to crustal microbes, and that this removal mechanism may account for at least 5% of the global loss of DOC in the deep ocean. Cool crustal circulation probably contributes to maintaining the deep ocean as a reservoir of ‘aged’ and refractory DOC by discharging the surviving organic carbon constituents that are molecularly degraded and depleted in14C and13C into the deep ocean.