State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu, China.
State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, China.
Nature. 2023 Jun;618(7967):974-980. doi: 10.1038/s41586-023-06077-6. Epub 2023 May 31.
Phosphorus is a limiting nutrient that is thought to control oceanic oxygen levels to a large extent. A possible increase in marine phosphorus concentrations during the Ediacaran Period (about 635-539 million years ago) has been proposed as a driver for increasing oxygen levels. However, little is known about the nature and evolution of phosphorus cycling during this time. Here we use carbonate-associated phosphate (CAP) from six globally distributed sections to reconstruct oceanic phosphorus concentrations during a large negative carbon-isotope excursion-the Shuram excursion (SE)-which co-occurred with global oceanic oxygenation. Our data suggest pulsed increases in oceanic phosphorus concentrations during the falling and rising limbs of the SE. Using a quantitative biogeochemical model, we propose that this observation could be explained by carbon dioxide and phosphorus release from marine organic-matter oxidation primarily by sulfate, with further phosphorus release from carbon-dioxide-driven weathering on land. Collectively, this may have resulted in elevated organic-pyrite burial and ocean oxygenation. Our CAP data also seem to suggest equivalent oceanic phosphorus concentrations under maximum and minimum extents of ocean anoxia across the SE. This observation may reflect decoupled phosphorus and ocean anoxia cycles, as opposed to their coupled nature in the modern ocean. Our findings point to external stimuli such as sulfate weathering rather than internal oceanic phosphorus-oxygen cycling alone as a possible control on oceanic oxygenation in the Ediacaran. In turn, this may help explain the prolonged rise of atmospheric oxygen levels.
磷是一种限制营养物质，被认为在很大程度上控制着海洋中的氧气水平。有人提出，在埃迪卡拉纪（约 6.35 亿至 5.39 亿年前）期间，海洋磷浓度的增加可能是氧气水平增加的驱动因素。然而，在此期间，人们对磷循环的性质和演化知之甚少。在这里，我们使用来自全球六个分布区的碳酸盐结合磷（CAP）来重建与全球海洋氧合作用同时发生的大负碳同位素漂移——舒兰漂移（SE）期间的海洋磷浓度。我们的数据表明，在 SE 的下降和上升支期间，海洋磷浓度呈脉冲式增加。使用定量生物地球化学模型，我们提出这种观察结果可以解释为海洋有机物质氧化过程中二氧化碳和磷的释放，主要来自硫酸盐，进一步来自二氧化碳驱动的陆地风化作用。总的来说，这可能导致有机黄铁矿的埋藏和海洋氧气的增加。我们的 CAP 数据似乎还表明，在 SE 期间，海洋缺氧的最大和最小程度下，海洋磷浓度相当。这一观察结果可能反映了磷循环和海洋缺氧循环的解耦，而不是现代海洋中它们的耦合性质。我们的研究结果表明，硫酸盐风化等外部刺激可能是控制埃迪卡拉纪海洋氧合作用的因素，而不是内部海洋磷-氧循环。反过来，这可能有助于解释大气氧气水平的长期上升。
