GLOBE Institute, University of Copenhagen, 1350 Copenhagen, Denmark;
GLOBE Institute, University of Copenhagen, 1350 Copenhagen, Denmark.
Proc Natl Acad Sci U S A. 2019 Sep 24;116(39):19352-19361. doi: 10.1073/pnas.1901178116. Epub 2019 Sep 9.
The proliferation of large, motile animals 540 to 520 Ma has been linked to both rising and declining O levels on Earth. To explore this conundrum, we reconstruct the global extent of seafloor oxygenation at approximately submillion-year resolution based on uranium isotope compositions of 187 marine carbonates samples from China, Siberia, and Morocco, and simulate O levels in the atmosphere and surface oceans using a mass balance model constrained by carbon, sulfur, and strontium isotopes in the same sedimentary successions. Our results point to a dynamically viable and highly variable state of atmosphere-ocean oxygenation with 2 massive expansions of seafloor anoxia in the aftermath of a prolonged interval of declining atmospheric pO levels. Although animals began diversifying beforehand, there were relatively few new appearances during these dramatic fluctuations in seafloor oxygenation. When O levels again rose, it occurred in concert with predicted high rates of photosynthetic production, both of which may have fueled more energy to predators and their armored prey in the evolving marine ecosystem.
5.4 亿至 5.2 亿年前，大型、能动动物的大量出现与地球上 O 含量的上升和下降都有关联。为了探索这个难题，我们根据来自中国、西伯利亚和摩洛哥的 187 个海洋碳酸盐样本的铀同位素组成，以大约百万年分辨率重建了全球海底氧化程度，并使用受同一沉积序列中的碳、硫和锶同位素约束的质量平衡模型模拟了大气和海洋表面的 O 含量。我们的结果表明，大气-海洋氧化作用具有动态的、高度可变的状态，在大气 pO 水平持续下降的长时间间隔之后，有 2 次大规模的海底缺氧扩张。尽管动物在此之前已经开始多样化，但在海底氧合作用的这些剧烈波动期间，新出现的物种相对较少。当 O 含量再次上升时，它与预测的高光合作用产量同时发生，这两者都可能为不断进化的海洋生态系统中的捕食者及其有装甲的猎物提供更多的能量。
