Both molecular clocks and the fossil record indicate that eukaryotic algae evolved by the late Paleoproterozoic Era (2500 to 1600 million years ago, Ma). However, the biomarker record of steranes does not reveal their presence until the early Tonian Period (1000 to 720 Ma), suggesting that eukaryotic algae were insignificant ecosystem members for some one billion years after they evolved. Here, we conducted high-temperature pyrolysis and fixed-bed catalytic hydropyrolysis of kerogen from the ca. 1400 Ma Xiamaling Formation, liberating a host of lipid molecules, including C27 to C29 steranes. With sterane to hopane ratios ranging up to 0.17, our results indicate the presence of significant populations of both red and green algae at 1400 Ma, some 600 million years earlier than previously recognized. These algae actively contributed to primary production in what may have been a nitrogen-starved marine basin.
Bibliografisk noteFunding Information:
The research was financially supported by the National Key Research and Development Program of China ( 2017YFC0603101 ), and DEC acknowledges funding from the Villum Foundation (Grant 16518 ). We also acknowledge funding from the National Natural Science Foundation of China ( 41530317 ) and the Strategic Priority Research Program of the Chinese Academy of Sciences ( XDA14010101 ). The authors thank Prof. Huitong Wang and Caiyun Wei for the GC-MS analysis of GC-MS, also Professors JingkuiMi and Yuhong Liao for their support with the gold-tube pyrolysis and HyPy experiments. We also appreciated the attention and time taken by two anonymous reviewers to evaluate this research.
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