Collaborative Research: Biosignatures of coupled iron and carbon cycling in ferruginous lakes

合作研究：含铁湖泊中铁和碳耦合循环的生物特征

• 批准号: 1660761
• 负责人: Chad Wittkop
• 金额: $ 9.52万
• 依托单位: Minnesota State University, Mankato
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-05-01 至 2022-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1660761&HistoricalAwards=false
• 关键词: Collaborative; Research; Biosignatures; coupled; iron

One of the grand challenges of Geobiology is to infer the classes of microbes that shaped the biosphere at the early stages of Earth evolution, and to understand the effects of their activities on the early oceans and atmosphere. The most direct way of addressing this challenge is to use modern environments that can be considered as analogues for those of early Earth. Such analogue environments are rare and valuable. This project will use two lakes in the Midwestern U.S. - Brownie Lake, MN and Canyon Lake, MI - whose waters were recently discovered to harbor abundant dissolved ferrous iron, which makes them good analogues for the anoxic "ferruginous" oceans that persisted for more than 2 billion years of Earth's history (during Archean and Proterozoic eons). Using field and analytical work, these researchers will investigate an early form of photosynthesis that relies on the redox cycling of iron (photoferrotrophy) and the corresponding cycle of methane, which would have been an important part of the ancient carbon cycle. This project will constrain the activity and biosignatures of the involved microorganisms. This is a necessary step to understand the rise of oxygen on Earth, the deposition of extensive iron-rich sediments that represent the majority of modern-day iron ore deposits, as well as major climate perturbations, and enigmatic carbon isotope excursions on the early Earth. A major emerging question is to what extent the greenhouse gas methane was generated and lost to the atmosphere in ferruginous oceans, and how this contributed to the global carbon cycle and climate. As prior investigations of ferruginous lakes as early Earth analogues utilized international sites, this project will serve U.S. scientists by establishing these two national research sites. The project will support two early career researchers, educate two graduate students, and involve several undergraduates in research. Project results and the established study sites will be used in hands-on graduate training in limnology. In collaboration with land managers of the two lakes, the project will provide a detailed physicochemical baseline to inform future water quality monitoring efforts in the lake watersheds, as well as will contribute to the City of Minneapolis environmental education outreach programs.   Photoferrotrophy is thought to have been the major pathway for primary productivity in ferruginous Precambrian oceans. However, current analogues - meromictic ferruginous lakes - either suffer from light limitation for photoferrotrophy, fix carbon through predominantly sulfurbased photosynthetic pathways, or are located in regions unsuitable for seasonal monitoring. Brownie Lake has sufficient light and an abundant community of anoxygenic phototrophs (including photoferrotrophs), and deeper Canyon Lake has an extended oxic-anoxic transition zone and much lower nutrients than Brownie Lake. Together, these lakes comprise a range of conditions to investigate the controls that varying nutrient levels, physiography, and seasonality have on photoferrotrophic primary productivity and methane cycling. The team will monitor aqueous and carbon isotope geochemistry, microbial community composition, and elemental makeup/mineralogy of particulates from the Brownie and Canyon Lake water columns in order to determine: (1) the physicochemical conditions that regulate the presence and activity of photoferrotrophs, (2) the role of resident microbes in iron and carbon cycling, (3) the inorganic and mineral biosignatures that similar microbial communities might have left in Precambrian iron-rich sediments such as Banded Iron Formations (BIF), and (4) the isotopic imprint of photoferrotrophy and methanogenesis/methanotrophy to carbon and iron cycling.

地球生物学的重大挑战之一是推断在地球演化早期阶段塑造生物圈的微生物类别，并了解它们的活动对早期海洋和大气的影响。解决这一挑战的最直接方法是使用可被视为早期地球环境的模拟环境的现代环境。这样的模拟环境是罕见且有价值的。该项目将利用美国中西部的两个湖泊——明尼苏达州的布朗尼湖和密歇根州的峡谷湖——最近发现这两个湖的水域含有丰富的溶解亚铁，这使它们成为地球历史上持续了超过 20 亿年（太古宙和元古代）的缺氧“含铁”海洋的良好类比。通过实地和分析工作，这些研究人员将研究依赖于铁的氧化还原循环（光铁营养）和相应的甲烷循环的早期形式的光合作用，这可能是古代碳循环的重要组成部分。该项目将限制相关微生物的活性和生物特征。这是了解地球上氧气的上升、代表大多数现代铁矿床的广泛富铁沉积物的沉积、以及主要气候扰动和早期地球上神秘的碳同位素偏移的必要步骤。一个新出现的主要问题是，含铁海洋中温室气体甲烷在多大程度上产生并流失到大气中，以及这对全球碳循环和气候有何影响。由于先前对铁质湖泊（作为早期地球类似物）的调查利用了国际站点，因此该项目将通过建立这两个国家研究站点来为美国科学家服务。该项目将支持两名早期职业研究人员，培养两名研究生，并让几名本科生参与研究。项目成果和已建立的研究地点将用于湖泊学研究生实践培训。该项目将与两个湖泊的土地管理者合作，提供详细的物理化学基线，为未来湖泊流域的水质监测工作提供信息，并将为明尼阿波利斯市的环境教育推广计划做出贡献。   光致铁营养被认为是含铁前寒武纪海洋初级生产力的主要途径。然而，目前的类似物——分聚铁色湖泊——要么受到光铁营养的光限制，通过主要基于硫的光合途径固定碳，要么位于不适合季节性监测的地区。布朗尼湖光照充足，有丰富的缺氧光养生物（包括光合铁养生物）群落，较深的峡谷湖具有延伸的好氧缺氧过渡区，营养成分比布朗尼湖低得多。这些湖泊共同构成了一系列条件，以研究不同的营养水平、地貌和季节性对光铁营养初级生产力和甲烷循环的控制。该团队将监测布朗尼和峡谷湖水柱的水和碳同位素地球化学、微生物群落组成以及颗粒的元素组成/矿物学，以确定：（1）调节光铁营养体的存在和活性的物理化学条件，（2）常驻微生物在铁和碳循环中的作用，（3）无机和矿物生物特征 类似的微生物群落可能留在前寒武纪富含铁的沉积物中，例如带状铁地层（BIF），以及（4）光致铁营养和产甲烷/甲烷营养对碳和铁循环的同位素印记。

项目成果

Evaluating a primary carbonate pathway for manganese enrichments in reducing environments

• DOI: 10.1016/j.epsl.2020.116201
• 发表时间: 2020-05
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: C. Wittkop;E. Swanner;A. Grengs;N. Lambrecht;M. Fakhraee;A. Myrbo;A. Bray;S. Poulton;S. Katsev

Biogeochemical and physical controls on methane fluxes from two ferruginous meromictic lakes

• DOI: 10.1111/gbi.12365
• 发表时间: 2019-10
• 期刊: Geobiology
• 影响因子: 3.7
• 作者: N. Lambrecht;S. Katsev;C. Wittkop;S. Hall;C. Sheik;A. Picard;M. Fakhraee;E. Swanner

The biogeochemistry of ferruginous lakes and past ferruginous oceans

• DOI: 10.1016/j.earscirev.2020.103430
• 发表时间: 2020-12
• 期刊: Earth-Science Reviews
• 影响因子: 12.1
• 作者: E. Swanner;N. Lambrecht;C. Wittkop;C. Harding;S. Katsev;J. Torgeson;S. Poulton