Stable isotope signatures of elements related to life such as carbon and nitrogen can be powerful biomarkers that provide key information on the biological origin of organic remains and their paleoenvironments. Marked advances have been achieved in the last decade in our understanding of the coupled evolution of biological carbon and nitrogen cycling and the chemical evolution of the early Earth thanks, in part, to isotopic signatures preserved in fossilized microbial mats and organic matter of marine origin. However, the geologic record of the early continental biosphere, as well as its evolution and biosignatures, is still poorly constrained. Following a recent report of direct fossil evidence of life on land at 3.22 Ga, we compare here the carbon and nitrogen isotopic signals of this continental Archean biosphere with biosignatures of cyanobacteria biological soil crusts (cyanoBSCs) colonizing modern arid environments. We report the first extended δ¹³C and δ¹⁵N data set from modern cyanoBSCs and show that these modern communities harbor specific isotopic biosignatures that compare well with continental Archean organic remains. We therefore suggest that cyanoBSCs are likely relevant analogs for the earliest continental ecosystems. As such, they can provide key information on the timing, extent, and possibly mechanism of colonization of the early Earth's emergent landmasses.

中文翻译：

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生物土壤结壳作为太古代大陆生物圈的现代类似物：碳和氮同位素的见解。

与生命有关的元素（例如碳和氮）的稳定同位素特征可能是强大的生物标记，可提供有关有机物及其古环境的生物学起源的关键信息。在过去的十年中，我们对生物碳和氮循环的耦合演化以及地球早期化学演化的理解取得了显着进展，部分是由于化石化微生物垫和海洋来源的有机物中保存的同位素特征。但是，早期大陆生物圈的地质记录及其演化和生物特征仍然受限制。在最近有一份有关3.22 Ga土地上生命直接化石证据的报告之后，我们在这里将这个大陆太古宙生物圈的碳和氮同位素信号与定居在现代干旱环境中的蓝细菌生物土壤结壳（cyanoBSCs）的生物特征进行比较。我们报告第一个扩展的δ¹³ C和δ ¹⁵的N个数据从现代cyanoBSCs和显示设置，这些现代社区滋生与欧式太古有机遗体比较以及特定同位素生物信号。因此，我们建议cyanoBSCs可能是最早的大陆生态系统的相关类似物。这样，它们可以提供有关地球早期涌现的陆地的定殖的时间，程度以及可能的机制的关键信息。