期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2020
卷号：117
期号：34
页码：20453-20461
DOI：10.1073/pnas.2003108117
出版社：The National Academy of Sciences of the United States of America
摘要：Subseafloor mixing of high-temperature hot-spring fluids with cold seawater creates intermediate-temperature diffuse fluids that are replete with potential chemical energy. This energy can be harnessed by a chemosynthetic biosphere that permeates hydrothermal regions on Earth. Shifts in the abundance of redox-reactive species in diffuse fluids are often interpreted to reflect the direct influence of subseafloor microbial activity on fluid geochemical budgets. Here, we examine hydrothermal fluids venting at 44 to 149 °C at the Piccard hydrothermal field that span the canonical 122 °C limit to life, and thus provide a rare opportunity to study the transition between habitable and uninhabitable environments. In contrast with previous studies, we show that hydrocarbons are contributed by biomass pyrolysis, while abiotic sulfate (SO 4 2− ) reduction produces large depletions in H 2 . The latter process consumes energy that could otherwise support key metabolic strategies employed by the subseafloor biosphere. Available Gibbs free energy is reduced by 71 to 86% across the habitable temperature range for both hydrogenotrophic SO 4 2− reduction to hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ) reduction to methane (CH 4 ). The abiotic H 2 sink we identify has implications for the productivity of subseafloor microbial ecosystems and is an important process to consider within models of H 2 production and consumption in young oceanic crust.
