西澳大利亚大学Birger Rasmussen及其研究小组认为富含营养的海洋为地球的氧化提供了养料。该研究于2023年3月9日发表于国际一流学术期刊《地质学》杂志上。

研究组报告了在大氧化事件开始之前，在海洋陆架(包括浅水相)沉积的2.46-2.40 Ga铁地层中磷酸钙纳米颗粒海水沉淀的证据。他们的模型表明，磷酸钙和硅酸亚铁(绿柱石)的共沉淀需要含铁海水，含铁海水中溶解的磷浓度比今天的透光层高出许多个数量级。如果这个观点是正确的，那么磷的有效性不太可能在大氧化事件之前抑制蓝细菌的扩张。在2.40 Ga之前不久，富含磷的地表水的储层可能最终通过推动初级生产力和有机碳埋藏的急剧增加而引发大气中氧的迅速上升。该研究小组推测，在2.32-2.06 Ga浅水碳酸盐岩中记录的神秘的Lomagundi事件的正碳同位素漂移，可能标志着向由养分有效性控制的高生物生产力的现代生物圈过渡的关键一步。

据悉，磷的可用性对全球海洋初级生产力产生重大影响。然而，在大氧化事件(GOE) 2.45-2.32 Ga开始之前，其丰度及其作为限制性营养素的作用尚不清楚。低浓度的海水磷被提出来解释产氧蓝细菌的早期出现和大气氧化开始之间的明显延迟。

附：英文原文

Title: Did nutrient-rich oceans fuel Earth’s oxygenation

Author: Birger Rasmussen, Janet R. Muhling, Nicholas J. Tosca, Woodward W. Fischer

Issue&Volume: 2023-03-09

Abstract: Phosphorus (P) availability exerts a strong influence on primary productivity in global oceans. However, its abundance and role as a limiting nutrient prior to the start of the Great Oxygenation Event (GOE) 2.45–2.32 Ga is unclear. Low concentrations of seawater P have been proposed to explain the apparent delay between the early appearance of oxygen-producing Cyanobacteria and the onset of atmospheric oxygenation. We report evidence for seawater precipitation of Ca-phosphate nanoparticles in 2.46–2.40 Ga iron formations deposited on a marine shelf, including shallow-water facies, immediately prior to the onset of the GOE. Our modeling shows that the co-precipitation of Ca-phosphate and ferrous silicate (greenalite) required ferruginous seawater with dissolved P concentrations many orders of magnitude higher than in today’s photic zone. If correct, it follows that P availability is unlikely to have suppressed the expansion of Cyanobacteria prior to the GOE. A reservoir of P-rich surface water shortly before 2.40 Ga could ultimately have triggered a rapid rise in atmospheric oxygen by fueling a sharp increase in primary productivity and organic-carbon burial. We speculate that the enigmatic Lomagundi positive carbon-isotope excursion, recorded in 2.32–2.06 Ga shallow-water carbonates, may mark a key step in the transition toward a modern biosphere of high biological productivity controlled by nutrient availability.

DOI: 10.1130/G50835.1

Source: https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G50835.1/620905/Did-nutrient-rich-oceans-fuel-Earth-s-oxygenationredirectedFrom=fulltext