Studying the response and recovery of marine microbial communities during mass extinction events provides an evolutionary window through which to understand the adaptation and resilience of the marine ecosystem in the face of significant environmental disturbances. The goal of this study is to reconstruct changes in the marine microbial community structure through the Late Devonian Frasnian-Famennian (F-F) transition. We performed a multiproxy investigation on a drill core of the Upper Devonian New Albany Shale from the Illinois Basin (western Kentucky, USA). Aryl isoprenoids show green sulfur bacteria expansion and associated photic zone euxinia (PZE) enhancement during the F-F interval. These changes can be attributed to augmented terrigenous influxes, as recorded collectively by the long-chain/short-chain normal alkane ratio, carbon preference index, C₃₀ moretane/C₃₀ hopane, and diahopane index. Hopane/sterane ratios reveal a more pronounced dominance of eukaryotic over prokaryotic production during the mass extinction interval. Sterane distributions indicate that the microalgal community was primarily composed of green algae clades, and their dominance became more pronounced during the F-F interval and continued to rise in the subsequent periods. The 2α-methylhopane index values do not show an evident shift during the mass extinction interval, whereas the 3β-methylhopane index values record a greater abundance of methanotrophic bacteria during the extinction interval, suggesting enhanced methane cycling due to intensified oxygen depletion. Overall, the Illinois Basin during the F-F extinction experienced heightened algal productivity due to intensified terrigenous influxes, exhibiting similarities to contemporary coastal oceans that are currently undergoing globalized cultural eutrophication. The observed microbial community shifts associated with the F-F environmental disturbances were largely restricted to the extinction interval, which suggests a relatively stable, resilient marine microbial ecosystem during the Late Devonian.

中文翻译：

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脂质生物标志物记录了弗拉斯年-法门年大规模灭绝事件期间海洋微生物群落结构的变化

研究大规模灭绝事件期间海洋微生物群落的响应和恢复提供了一个进化窗口，通过该窗口了解海洋生态系统面对重大环境干扰时的适应和恢复力。本研究的目标是重建晚泥盆世弗拉斯尼期-法门期（FF）过渡期间海洋微生物群落结构的变化。我们对伊利诺伊州盆地（美国肯塔基州西部）上泥盆统新奥尔巴尼页岩的钻芯进行了多代理调查。芳基类异戊二烯在 FF 期间表现出绿色硫细菌扩张和相关的透光区 (PZE) 增强。这些变化可归因于陆源流入的增加，如长链/短链正烷烃比率、碳偏好指数、C ₃₀摩尔烷/C ₃₀藿烷和二藿烷指数共同记录的。藿烷/甾烷比率揭示了在大规模灭绝期间真核生物相对于原核生物的生产具有更明显的优势。甾烷分布表明微藻群落主要由绿藻分支组成，其优势在FF期间变得更加明显，并在随后的时期继续上升。在大规模灭绝间隔期间，2α-甲基藿烷指数值没有显示出明显的变化，而3β-甲基藿烷指数值在灭绝间隔期间记录了更丰富的甲烷氧化细菌，这表明由于氧气消耗加剧而导致甲烷循环增强。总体而言，FF灭绝期间的伊利诺伊州盆地由于陆源流入加剧而经历了藻类生产力的提高，这与目前正在经历全球文化富营养化的当代沿海海洋有相似之处。观察到的与 FF 环境扰动相关的微生物群落变化很大程度上局限于灭绝间隔，这表明晚泥盆世有一个相对稳定、有弹性的海洋微生物生态系统。