The rise of algae in Cryogenian oceans and the emergence of animals
The rise of algae in Cryogenian oceans and the emergence of animals
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DOI：
10.1038/nature23457
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发表时间：
2017-08-31
期刊：
影响因子：
64.8
通讯作者：
Liyanage, Tharika
中科院分区：
文献类型：
--
作者：
Brocks, Jochen J.;Jarrett, Amber J. M.;Liyanage, Tharika
从优势细菌向真核海洋初级生产力的转变是地球历史上最深刻的生态革命之一，它重新组织了水体中碳和营养物质的分布，并增加了向更高营养级的能量流。但这种转变的原因和地质时间，以及与大气中氧气含量上升(1)和动物进化(2)的可能联系，仍然不清楚。在这里，我们展示了真核类固醇的分子化石记录，证明细菌是成冰期（720-6.35 亿年前）之前海洋中唯一值得注意的初级生产者。类固醇多样性和丰度的增加标志着海洋浮游藻类（Archaeplastida）在659-6.45亿年前斯图尔蒂安和马里诺“雪球地球”冰川作用之间的狭窄时间间隔内迅速崛起。我们认为，蓝藻的地位被斯图尔蒂安冰消期提供的大量营养物质所打破(3)。 “藻类的崛起”创造了具有更有效的营养和能量转移的食物网(4)，推动生态系统向更大、更复杂的生物体发展。这种效应是由海绵 (5) 和掠食性根茎动物生物标志物的同时出现以及随后埃迪卡拉纪真后生动物的辐射 (2) 记录的。
The transition from dominant bacterial to eukaryotic marine primary productivity was one of the most profound ecological revolutions in the Earth's history, reorganizing the distribution of carbon and nutrients in the water column and increasing energy flow to higher trophic levels. But the causes and geological timing of this transition, as well as possible links with rising atmospheric oxygen levels(1) and the evolution of animals(2), remain obscure. Here we present a molecular fossil record of eukaryotic steroids demonstrating that bacteria were the only notable primary producers in the oceans before the Cryogenian period (720-635 million years ago). Increasing steroid diversity and abundance marks the rapid rise of marine planktonic algae (Archaeplastida) in the narrow time interval between the Sturtian and Marinoan 'snowball Earth' glaciations, 659-645 million years ago. We propose that the incumbency of cyanobacteria was broken by a surge of nutrients supplied by the Sturtian deglaciation(3). The 'Rise of Algae' created food webs with more efficient nutrient and energy transfers(4), driving ecosystems towards larger and increasingly complex organisms. This effect is recorded by the concomitant appearance of biomarkers for sponges(5) and predatory rhizarians, and the subsequent radiation of eumetazoans in the Ediacaran period(2).