Ediacaran reorganization of the marine phosphorus cycle
Ediacaran reorganization of the marine phosphorus cycle
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DOI：
10.1073/pnas.1916738117
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发表时间：
2020-06-02
影响因子：
11.1
通讯作者：
Knoll, Andrew H.
中科院分区：
文献类型：
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作者：
Laakso, Thomas A.;Sperling, Erik A.;Knoll, Andrew H.
埃迪卡拉纪(635-541 Ma)标志着全球向更具生产力的生物圈的过渡，其证据是食物和氧化剂的可获得性增加，宏观动物的出现，真核浮游植物的大量种群，以及大规模磷矿沉积的开始。我们认为，这一整套变化的结果是深海海洋磷水库规模的扩大，与硫酸盐浓度上升和硫酸盐还原细菌对有机磷的再矿化增加有关。受现代缺氧盆地的制约，简单的物质平衡计算表明，深水磷酸盐浓度可能增加了一个数量级，而大陆输入磷的速度没有任何增加。值得注意的是，尽管磷矿沉积发生了重大变化，但新元古代和早古生代磷含量的新汇编显示，中值几乎没有长期变化，支持了再矿化而不是侵蚀磷通量的变化是观察到的磷矿积累变化的主要驱动因素的观点。这些变化的触发因素可能是短暂的新元古代风化事件，其生物地球化学后果是由氧和硫循环介导的一系列正反馈所维持的，导致埃迪卡拉纪末期生物地球化学循环、初级生产力和生物多样性的永久状态变化。
The Ediacaran Period (635 to 541 Ma) marks the global transition to a more productive biosphere, evidenced by increased availability of food and oxidants, the appearance of macroscopic animals, significant populations of eukaryotic phytoplankton, and the onset of massive phosphorite deposition. We propose this entire suite of changes results from an increase in the size of the deep-water marine phosphorus reservoir, associated with rising sulfate concentrations and increased remineralization of organic P by sulfate-reducing bacteria. Simple mass balance calculations, constrained by modern anoxic basins, suggest that deep-water phosphate concentrations may have increased by an order of magnitude without any increase in the rate of P input from the continents. Strikingly, despite a major shift in phosphorite deposition, a new compilation of the phosphorus content of Neoproterozoic and early Paleozoic shows little secular change in median values, supporting the view that changes in remineralization and not erosional P fluxes were the principal drivers of observed shifts in phosphorite accumulation. The trigger for these changes may have been transient Neoproterozoic weathering events whose biogeochemical consequences were sustained by a set of positive feedbacks, mediated by the oxygen and sulfur cycles, that led to permanent state change in biogeochemical cycling, primary production, and biological diversity by the end of the Ediacaran Period.