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.

在大部分海洋中，微生物生命并不缺乏碳、氮或氧;相反，缺乏的是磷和必需的微量金属，例如，铁、钼、镍、钴和锌，限制微生物增殖和生产力。这可能是真的，因为超过38亿年前（Ga）生命的曙光，当微生物开始进化复杂的金属清除策略，以纳入溶质从他们的水环境。海水中微量金属的可用性部分受到长期地质过程的控制，但也受到海洋生物圈活动的影响，海洋生物圈以多种方式控制其物种形成和分布。在过去的十年中，我已经开发了一个广泛的数据库中的微量金属浓度的带状铁地层（BIF）和页岩，揭示了长期的趋势，在其可用性在地球的历史过程中。然而，至关重要的是，我们进一步解释这些数据的能力受到微生物如何影响水柱中微量金属循环的不确定性的阻碍，这种影响如何在地质时间尺度上演变，以及微生物谱系的演变如何记录在古代沉积记录中。解决这些不确定性是我的研究计划的一个新的轨迹，我认为这对实现我更好地理解生命和前寒武纪环境的共同进化的长期目标至关重要。因此，在这个NSERC DG提案中，我详细介绍了4个短期目标，重点是通过实验确定浮游植物如何影响我们古老星球微生物主导的海洋生态系统中的微量金属可用性。然后，我将把这些知识应用于记录地球表面系统根本变化的古元古代沉积矿床，如2.45-2.32 Ga大氧化事件和2.22-2.06 Ga Lomagundi-Jatuli事件。 目标（1-3）将通过实验确定微量金属在海洋浮游植物、细胞裂解物和粘土中的分配;现存的海洋光合自养生物是否具有可用作岩石记录中生物特征的诊断性微量金属成分;以及古代海洋中相对更丰富的溶解有机物对金属形态的影响是否与今天不同。目标（4）将利用这些结果更好地了解古元古代海洋沉积物化学成分的控制。这些项目将大量利用我当时广泛的BIF和页岩地球化学数据库，包括来自澳大利亚、南非、北美、巴西、中国和芬诺斯坎迪亚的岩石。最终目标将是提高我们对地球古代海洋的营养景观和细菌多样性的理解。