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Probing Earth's earliest ecosystems: a multi-proxy study of the ~2.7 Ga Belingwe Greenstone Belt, Zimbabwe

探索地球最早的生态系统：对津巴布韦~2.7 Ga Belingwe 绿岩带的多代理研究

基本信息

批准号：
NE/M001768/1
负责人：
Euan Nisbet
金额：
$ 14.72万
依托单位：
Royal Holloway University of London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2015
资助国家：
英国
起止时间：
2015 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FM001768%2F1
关键词：
Probing Earth earliest ecosystems multi

项目摘要

Biology has been a major driver for global change since the very earliest stages of our planetary history. Life first evolved on Earth as early as 3.8 billion years ago, but for the first ~3 billion years it was composed entirely of small unicellular organisms lacking a nucleus (prokaryotes). Unlike their larger eukaryotic counterparts which mainly use oxygen and organic carbon as fuel for respiration, prokaryotes have diverse metabolisms that produce energy from a wide array of chemical compounds, including sulfide, methane, and even toxic metals. These metabolisms catalyse chemical reactions that only proceed rapidly with biological intervention, and their products can have an irrevocable effect on the chemistry of the environment. The modern Earth environment carries the irrefutable imprint of current and past biochemical reactions, as does the geologic record of past environments. Before ~2.4 billion years ago, Earth's atmosphere was dominated by carbon dioxide and methane (with little to no oxygen), and the oceans were rich in dissolved iron and, periodically, sulfide. This environment was inhospitable to large multi-cellular organisms, but prokaryotic ("microbial") ecosystems thrived. Sometime around ~2.7 billion years ago, organisms called cyanobacteria (the precursors to modern plants) evolved the ability to generate energy and biomass by combining H2O with CO2 in the presence of sunlight. This newly developed metabolism, termed oxygenic photosynthesis, constituted a major biological innovation and significantly increased the efficiency of global carbon cycling. Of particular significance to our history of planetary change - the waste product of this metabolism was molecular oxygen, which subsequently began to accumulate in the environment for the first time ever. The eventual buildup of oxygen in the atmosphere, termed the Great Oxidation Event, was a prerequisite for the evolution of animals and multi-cellular organisms, and eventually enabled the global biosphere that we inhabit today. Despite the importance of progressive oxygenation on the early Earth, geoscientists still lack a fundamental understanding of how ancient ecosystems contributed to oxygen production and responded to molecular oxygen in the environment. Central to unravelling feedbacks between global carbon fixation and oxygen production is understanding the changes in the cycling of other biologically-required nutrients that react with O2. Nitrogen, in particular, is ubiquitous to life and required for the formation of nearly all biomolecules, including nucleic acids (DNA and RNA) and proteins. The marine nitrogen cycle is driven largely by biological processes which produce changes that can be measured in nitrogen-bearing compounds and isotopes preserved in the rock record. This research seeks to investigate the interplay of elemental transformations in early microbial ecosystems, using geochemical analyses of pristine sediments that formed ~2.7 billion years ago. Of central importance to this project are new drill cores that are extremely well-preserved for rocks of this time period, and include some of the earliest evidence for fossilized microbial ecosystems (possibly including cyanobacteria). We will measure proxies for biogeochemical N, C, and S cycling, along with additional geochemical analyses for oxygen availability, to examine interactions between the oxygen, carbon, sulfur, and nitrogen cycles during early biospheric evolution. These records from ~2.7 billion year old rocks will contribute to our fundamental understanding of the chemical and biological evolution of Earth's surface environments during the time period most closely associated with cyanobacterial evolution, a prerequisite to biospheric oxygenation and the proliferation of complex life on Earth.

从地球历史的最初阶段开始，生物学就一直是全球变化的主要驱动力。早在38亿年前，地球上就出现了生命，但在最初的30亿年里，生命完全由没有细胞核的小型单细胞生物（原核生物）组成。与大型真核生物不同，真核生物主要使用氧气和有机碳作为呼吸的燃料，原核生物具有多种代谢，从各种化合物中产生能量，包括硫化物，甲烷，甚至有毒金属。这些代谢催化的化学反应只有在生物干预下才能迅速进行，它们的产物可以对环境的化学产生不可逆转的影响。现代地球环境带有当前和过去生物化学反应的无可辩驳的印记，就像过去环境的地质记录一样。在大约24亿年前，地球的大气主要由二氧化碳和甲烷组成（几乎没有氧气），海洋富含溶解的铁和周期性的硫化物。这种环境不适合大型多细胞生物生存，但原核生物（“微生物”）生态系统却蓬勃发展。大约27亿年前，一种叫做蓝藻的生物（现代植物的前身）进化出了在阳光下将水和二氧化碳结合产生能量和生物量的能力。这种新发展的代谢被称为含氧光合作用，是一项重大的生物学创新，显著提高了全球碳循环的效率。在我们地球变化的历史上，这种新陈代谢的废物是分子氧，它随后开始在环境中积累，这是有史以来第一次。大气中氧气的最终积累，被称为大氧化事件，是动物和多细胞生物进化的先决条件，并最终形成了我们今天居住的全球生物圈。尽管渐进氧合作用在早期地球上很重要，但地球科学家仍然缺乏对古代生态系统如何促进氧气产生和对环境中的分子氧作出反应的基本理解。解开全球碳固定和氧气生产之间的反馈关系的核心是理解其他生物所需的营养物质与氧气反应的循环变化。尤其是氮，它在生命中无处不在，几乎所有生物分子的形成都需要氮，包括核酸（DNA和RNA）和蛋白质。海洋氮循环主要是由生物过程驱动的，生物过程产生的变化可以通过岩石记录中保存的含氮化合物和同位素来测量。本研究旨在通过对27亿年前形成的原始沉积物的地球化学分析，研究早期微生物生态系统中元素转化的相互作用。对这个项目至关重要的是新的岩心，这些岩心对于这个时期的岩石来说保存得非常好，其中包括一些微生物生态系统化石的最早证据（可能包括蓝藻）。我们将测量生物地球化学N、C和S循环的代理，以及额外的氧气可用性地球化学分析，以检查早期生物圈演化中氧、碳、硫和氮循环之间的相互作用。这些来自约27亿年前岩石的记录将有助于我们对地球表面环境的化学和生物进化的基本理解，这一时期与蓝藻进化密切相关，蓝藻进化是生物圈氧化和地球上复杂生命增殖的先决条件。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Secular mantle oxidation across the Archean-Proterozoic boundary: Evidence from V partitioning in komatiites and picrites

DOI：
10.1016/j.gca.2019.01.037
发表时间：
2019-04-01
期刊：
GEOCHIMICA ET COSMOCHIMICA ACTA
影响因子：
5
作者：
Nicklas, Robert W.;Puchte, Igor S.;Anbar, Ariel D.
通讯作者：
Anbar, Ariel D.

Ammonium availability in the Late Archaean nitrogen cycle

DOI：
10.1038/s41561-019-0371-1
发表时间：
2019-07
期刊：
Nature Geoscience
影响因子：
18.3
作者：
Jie Yang;C. Junium;N. Grassineau;E. Nisbet;G. Izon;G. Izon;C. Mettam;Anthony J. Martin;Aubrey L. Zerkle
通讯作者：
Jie Yang;C. Junium;N. Grassineau;E. Nisbet;G. Izon;G. Izon;C. Mettam;Anthony J. Martin;Aubrey L. Zerkle

Nitrogen Cycling in ~2.7Ga Oceans (Abstract)

~2.7Ga 海洋中的氮循环（摘要）