Collaboratice Research: Stable isotope tracers of the subsurface biosphere and its geochemical effects in oceanic ridge flank basement

海底下存在着一个巨大的地下生物圈，但对于微生物如何影响海水和大洋基底之间的化学交换，或者这如何影响全球地球化学收支，人们几乎不了解。最近的研究表明，微生物在改变海底火山岩方面发挥了积极作用，新的同位素技术已经开发出来，可以告诉人们发生改变的温度。这项研究利用美国国家科学基金会资助的大洋钻探计划采集的蚀变海底镁铁质熔岩中硫和氧的稳定同位素，以(1)追踪大洋底部的地下生物圈的分布，(2)了解微生物过程如何影响海水与地壳之间的化学和同位素交换，以及(3)确定微生物过程对海洋地球化学循环的影响。这是这类研究的第一次，因此它向我们提供关于深层生物圈生命的信息的能力具有潜在的变革性。研究将涉及沿大洋中脊侧翼的冷流体下涌地点岩石中的硫含量和同位素。还将分析从温暖和凉爽的地点吸附到氢氧化铁上的磷酸盐的氧同位素组成，以检查现场生物活动的影响，并估计微生物代谢过程发生的温度，从而了解海洋地壳中生命延伸到的深度。这项工作的更广泛影响包括支持一名非裔美国女研究人员，以及对本科生和博士后进行最先进的稳定同位素技术培训。纽黑文CT地区的少数民族高中生也将从事实验室研究。此外，纽黑文的皮博迪博物馆和密歇根大学纳米岩石夏令营将开展与该项目相关的公众宣传活动。这项工作将把研究成果纳入课程，并支持这两个机构的分析设施。

A vast subsurface biosphere exists beneath the seafloor, but there is little understanding of exactly how microbes affect chemical exchange between seawater and oceanic basement, or how this affects global geochemical budgets. Recent research shows that microbes have an active role in altering the volcanic rocks on the seafloor, and new isotope techniques have been developed that can tell the temperatures at which the alteration has taken place. This research uses the stable isotopes of sulfur and oxygen in altered seafloor mafic lavas sampled by NSF-funded Ocean Drilling Program to (1) trace the distribution of the subsurface biosphere in the oceanic basement, (2) understand how microbial processes affect chemical and isotope exchange between seawater and the crust, and (3) determine the influence of microbial processes on geochemical cycling in the oceans. This is the first study of its kind, and as such is potentially transformative in terms of its ability to inform us about life in the deep biosphere. Research will involve the sulfur contents and isotopes in rocks from cool fluid downwelling sites along the flanks of mid-ocean ridges. The oxygen isotope compositions of phosphate adsorbed to iron-oxyhydroxides from warm and cool sites will also be analyzed to examine the effects of in-situ biological activity and estimate the temperature at which microbial metabolic processes are occurring, giving an idea of the depth in the ocean crust to which life extends. The broader impacts of the work include support of an African American female researcher and the training of undergraduates and a postdoc in state-of-the-art stable isotope techniques. Minority high school students in the New Haven CT area will also be engaged in the laboratory research. In addition, public outreach associated with the project will be carried out by the Peabody Museum in New Haven and the University of Michigan Nano-Rocks summer high school camp. The work will incorporate research results into courses and support analytical facilities at both institutions.