Section 3.3: Earth Surface Geochemistry Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Telegrafenberg, Potsdam, 14473, Germany.
Division 1.1: Inorganic Trace Analysis, BAM, Federal Institute for Materials Research and Testing, Richard-Willstätter-Straße 11, Berlin, 12489, Germany.
Nat Commun. 2017 Sep 20;8(1):621. doi: 10.1038/s41467-017-00586-5.
The Cambrian explosion, the rapid appearance of most animal phyla in the geological record, occurred concurrently with bottom seawater oxygenation. Whether this oxygenation event was triggered through enhanced nutrient supply and organic carbon burial forced by increased continental weathering, or by species engaging in ecosystem engineering, remains a fundamental yet unresolved question. Here we provide evidence for several simultaneous developments that took place over the Ediacaran-Cambrian transition: expansion of siliceous sponges, decrease of the dissolved organic carbon pool, enhanced organic carbon burial, increased phosphorus removal and seawater oxygenation. This evidence is based on silicon and carbon stable isotopes, Ge/Si ratios, REE-geochemistry and redox-sensitive elements in a chert-shale succession from the Yangtze Platform, China. According to this reconstruction, sponges have initiated seawater oxygenation by redistributing organic carbon oxidation through filtering suspended organic matter from seawater. The resulting increase in dissolved oxygen levels potentially triggered the diversification of eumetazoans.The Ediacaran-Cambrian oxygenation of seawater is thought to have been caused by lifeforms engaging in ecosystem engineering. Here, the authors show that siliceous sponges increased seawater dissolved oxygen concentrations by redistributing organic carbon oxidation through filtering suspended organic matter.
寒武纪大爆发是指在地质记录中大多数动物门的快速出现，与底层海水的氧气化同时发生。这种氧气化事件是通过增加的大陆风化作用所带来的营养供应和有机碳埋藏的增强而引发的，还是通过物种进行生态系统工程引发的，这仍然是一个基本但尚未解决的问题。在这里，我们提供了在埃迪卡拉纪-寒武纪过渡时期同时发生的几个发展的证据：硅质海绵的扩张、溶解有机碳库的减少、有机碳埋藏的增加、磷的去除和海水氧气化。这一证据基于来自中国扬子台地的燧石-页岩序列中的硅和碳稳定同位素、Ge/Si 比值、REE 地球化学和氧化还原敏感元素。根据这一重建，海绵通过从海水中过滤悬浮有机物来重新分配有机碳氧化，从而启动了海水氧气化。溶解氧水平的增加可能潜在地引发后生动物的多样化。人们认为，埃迪卡拉纪-寒武纪时期海水的氧气化是由参与生态系统工程的生命形式引起的。在这里，作者表明，硅质海绵通过过滤悬浮有机物来重新分配有机碳氧化，从而增加了海水的溶解氧浓度。
