Methanogenesis and sulfate reduction in marine sediments: A new model
Methanogenesis and sulfate reduction in marine sediments: A new model
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DOI：
10.1016/j.epsl.2010.04.009
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发表时间：
2010-07
影响因子：
5.3
通讯作者：
R. Mitterer
中科院分区：
文献类型：
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作者：
R. Mitterer
许多研究表明，在某些条件下，在硫酸盐存在下，产甲烷菌是活跃的。这一现象在南澳大利亚大陆边缘的碳酸盐沉积物中尤为明显。在大澳大利亚湾的大洋钻探计划第182航段期间，有三个地点在近500米的沉积物中含有高浓度的微生物生成的甲烷和硫化氢。在这些岩心中，硫酸盐还原带和产甲烷带完全重叠，也就是说，通常的硫酸盐-甲烷过渡带是不存在的。氨基酸外消旋数据表明，含气沉积物由比低含气部位年轻的碳酸盐组成。还原气体的高浓度也出现在巴哈马地台边缘的两个ODP点，这两个点的沉积条件都与182腿的高含气点相似。这些还原气体的共生是一种不寻常的条件组合的结果，包括：(1)厚的第四系贫铁碳酸盐沉积序列，(2)海底卤水，和(3)中等数量的有机碳。在所有这些地点以及在其他已报道的环境中，硫化氢和甲烷共同产生的可能解释是，产甲烷菌正在利用非竞争性底物在硫酸盐还原带内产生甲烷。综上所述，这些结果构成了海洋沉积物中硫酸盐还原和产甲烷的新模型的基础。该模型的生物地球化学终端是：(1)微量硫酸盐还原，(2)硫酸盐完全还原，然后产甲烷，(3)重叠的硫酸盐还原和产甲烷，没有过渡带。
A number of studies have shown that methanogens are active in the presence of sulfate under some conditions. This phenomenon is especially exemplified in carbonate sediments of the southern Australian continental margin. Three sites cored during Ocean Drilling Program (ODP) Leg 182 in the Great Australian Bight have high concentrations of microbially-generated methane and hydrogen sulfide throughout almost 500m of sediments. In these cores, the sulfate-reducing and methanogenic zones overlap completely; that is, the usual sulfate-methane transition zone is absent. Amino acid racemization data show that the gassy sediments consist of younger carbonates than the low-gas sites. High concentrations of the reduced gases also occur in two ODP sites on the margin of the Bahamas platform, both of which have similar sedimentary conditions to those of the high-gas sites of Leg 182. Co-generation of these reduced gases results from an unusual combination of conditions, including: (1) a thick Quaternary sequence of iron-poor carbonate sediments, (2) a sub-seafloor brine, and (3) moderate amounts of organic carbon. The probable explanation for the co-generation of hydrogen sulfide and methane in all these sites, as well as in other reported environments, is that methanogens are utilizing non-competitive substrates to produce methane within the sulfate-reducing zone. Taken together, these results form the basis of a new model for sulfate reduction and methanogenesis in marine sediments. The biogeochemical end-members of the model are: (1) minimal sulfate reduction, (2) complete sulfate reduction followed by methanogenesis, and (3) overlapping sulfate reduction and methanogenesis with no transition zone.