The Paleoproterozoic marine biosphere: Impacts on the ancient Earth surface system

古元古代海洋生物圈：对古代地球表面系统的影响

• 批准号: RGPIN-2020-05189
• 负责人: Konhauser, Kurt
• 金额: $ 8.3万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=750903
• 关键词: Paleoproterozoic; marine; biosphere; Impacts; ancient

Throughout much of the oceans, microbial life is not lacking carbon, nitrogen or oxygen; instead, it is the scarcity of phosphorous and essential trace metals, e.g., iron, molybdenum, nickel, cobalt and zinc, that limits microbial proliferation and productivity. This has likely been true since the dawn of life over 3.8 billion years ago (Ga) when microbes began evolving elaborate metal scavenging strategies to incorporate solutes from their aqueous milieu. Trace metal availability in seawater is, in part, controlled by long-term geological processes, yet is also affected by the activity of the marine biosphere that controls their speciation and distribution in a myriad of ways. Over the last decade, I have developed an extensive database of trace metal concentrations in both banded iron formations (BIF) and shales that have revealed secular trends in their availability over the course of Earth's history. Critically, however, our ability to interpret this data further is hampered by uncertainties about how microbes affected trace metal cycling in the water column, how this influence may have evolved over geological timescales, and how the evolution of microbial lineages may be recorded in ancient sedimentary records. Resolving these uncertainties is a new trajectory of my research program which I consider critical to fulfilling my long-term aim of better understanding the co-evolution of life and the Precambrian environment. Therefore, in this NSERC DG proposal, I have detailed 4 short-term objectives focused on experimentally determining how phytoplankton may have impacted trace metal availability in the microbially-dominated marine ecosystems of our ancient planet. I will then apply this knowledge to critical Paleoproterozoic sedimentary deposits that record fundamental changes to the Earth surface system, such as the 2.45-2.32 Ga Great Oxidation Event and the 2.22-2.06 Ga Lomagundi-Jatuli Event. Objectives (1-3) will experimentally determine the partitioning of trace metals to marine phytoplankton, cell lysates and clay; if extant marine photoautotrophs possess diagnostic trace metal compositions that can be used as biosignatures in the rock record; and whether the relatively more abundant dissolved organic matter in ancient oceans impacted metal speciation differently from today. Objective (4) will then use those results to better understand the controls on the chemical composition of marine sediments from the Paleoproterozoic. These projects will draw heavily on my extensive geochemical database of BIF and shales from that time, including rocks from Australia, South Africa, North America, Brazi, Chinal and Fennoscandia. The ultimate goal will be to improve our understanding of the nutrient landscape and bacterial diversity of Earth's ancient oceans.

在整个海洋中，微生物寿命并不缺少碳，氮或氧气。取而代之的是，磷，钼，镍，钴和锌的磷和必需痕量金属的稀缺限制了微生物增殖和生产力。自38亿年前（GA）生命的曙光以来，当微生物开始发展精美的金属清除策略以纳入其水环中的溶质时，这可能是如此。海水中的痕量金属可用性部分受长期地质过程控制，但也受到海洋生物圈活性的影响，该活动以多种方式控制其物种物种和分布。在过去的十年中，我在带状铁层（BIF）和页岩中开发了广泛的痕量金属浓度数据库，这些数据库揭示了其在地球历史过程中其可用性的世俗趋势。然而，至关重要的是，我们进一步解释这些数据的能力受到关于微生物如何影响水柱中的痕量金属循环的不确定性，这种影响如何在地质时间范围内进化，以及如何在古代沉积物中记录微生物谱系的演变。解决这些不确定性是我的研究计划的新轨迹，我认为这对于实现我的长期目标是更好地理解生活和前寒武纪环境的长期目标。因此，在这项NSERC DG提案中，我详细介绍了4个短期目标，旨在通过实验确定浮游植物如何影响我们古代星球的微生物海洋生态系统中的痕量金属可用性。然后，我将将这些知识应用于关键的古植物学沉积沉积物，这些沉积物记录了地面表面系统的基本变化，例如2.45-2.32 GA GA大氧化事件和2.22-2.06 Ga Lomagundi-Jatuli事件。 目标（1-3）将通过实验确定将痕量金属分配到海洋浮游植物，细胞裂解物和粘土中。如果现存的海洋光自动营养物具有诊断性痕量金属成分，可以用作岩石记录中的生物签名；以及古代海洋中相对较丰富的有机物是否与今天不同。目标（4）然后将使用这些结果更好地了解古元古代海洋沉积物的化学成分的控制。这些项目将大大吸引我从那时起的广泛的BIF和页岩数据库，包括来自澳大利亚，南非，北美，Brazi，Chinal和Fennoscandia的岩石。最终目标是提高我们对地球古海洋养分景观和细菌多样性的理解。