Research School of Earth Sciences, The Australian National University, Canberra, Australian Capital Territory 2601, Australia.
Max Planck Institute for Biogeochemistry, Hans-Knoell-Straße 10, 07745 Jena, Germany.
Nature. 2017 Aug 31;548(7669):578-581. doi: 10.1038/nature23457. Epub 2017 Aug 16.
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 and the evolution of animals, 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. The 'Rise of Algae' created food webs with more efficient nutrient and energy transfers, driving ecosystems towards larger and increasingly complex organisms. This effect is recorded by the concomitant appearance of biomarkers for sponges and predatory rhizarians, and the subsequent radiation of eumetazoans in the Ediacaran period.
从优势细菌到真核海洋初级生产力的转变是地球历史上最深远的生态革命之一，它重新组织了水柱中碳和营养物质的分布，并增加了能量流向更高的营养级。但是，这种转变的原因和地质时间以及与大气氧气水平上升和动物进化的可能联系仍然不清楚。在这里，我们提出了真核甾醇的分子化石记录，证明在冰川纪（7.2 亿至 6.35 亿年前）之前，细菌是海洋中唯一显著的初级生产者。甾醇多样性和丰度的增加标志着海洋浮游藻类（古生菌）在 Sturtian 和 Marinoan“雪球地球”冰川作用之间狭窄的时间间隔内的快速崛起，大约在 6.59 亿至 6.45 亿年前。我们提出，蓝细菌的统治地位被 Sturtian 融冰提供的养分激增所打破。“藻类的兴起”创造了具有更高效率养分和能量转移的食物网，使生态系统朝着更大和越来越复杂的生物发展。这种效应记录在海绵和捕食根足类生物的生物标志物的同时出现，以及后生动物在埃迪卡拉纪的随后辐射中。
