Ordovician cyanobacterial calcification: A marine fossil proxy for atmospheric CO2
Ordovician cyanobacterial calcification: A marine fossil proxy for atmospheric CO2
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奥陶纪蓝藻钙化：大气二氧化碳的海洋化石代表
DOI：
10.1016/j.epsl.2019.115950
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发表时间：
2020-01-15
影响因子：
5.3
通讯作者：
Riding, Robert
中科院分区：
文献类型：
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作者：
Liu, Lijing;Liang, Liyuan;Riding, Robert
奥陶纪大气CO2水平对气候和生命有重要影响。然而，奥陶纪CO2的模拟估计差异很大，与随后的中生代相比，他们缺乏化石代理约束。在体内蓝藻鞘钙化，促进二氧化碳浓缩机制（CCM），创造独特的微体化石。这些提供了一个直接的生态生理联系到环境中的CO2浓度，并在较小程度上，O-2。蓝藻在高浓度的二氧化碳下不会钙化。实验表明，CCM可以诱导在当今的蓝藻在CO2水平低于类似于10倍目前的大气水平（PAL），这促进鞘钙化。我们编制了一个全球数据库的蓝藻钙化在整个奥陶纪（485-443万年前）的海洋环境中，并将其与模拟的估计大气中的CO2和O-2。这些数据表明，许多属的海洋钙化蓝藻重新出现在寒武纪系列2或首次出现在全球晚中晚上奥陶世（晚Darriwilian晚Katian）碳酸盐台地相，导致以前未被认识的全球多样性增加了10倍。钙化的如此大的增加表明在蓝细菌中CCM表达的广泛诱导，与外部CO2浓度持续下降低于类似于10 x PAL，以及溶解O-2水平的增加相一致，在Darriwilian晚期，Sandbian和Katian阶段，类似于460-445百万年前。这些蓝藻钙化化石代理数据提供了一个一阶的奥陶纪大气CO2模拟估计的约束。COPSE和最近的GEOCARB模型的CO2输出估计大致与奥陶纪的蓝藻钙化代理一致。鉴于蓝藻的悠久历史，钙化蓝藻代理提供了潜在的帮助解释二氧化碳更深入到地质时代。(C)2019爱思唯尔B. V.保留所有权利。
Ordovician atmospheric CO2 level was an important influence on climate and life. However, modelled estimates of Ordovician CO2 differ widely and, in contrast to much of the subsequent Phanerozoic, they lack fossil proxy constraints. In vivo cyanobacterial sheath calcification, promoted by carbon dioxide concentrating mechanisms (CCMs), creates distinctive microfossils. These provide a direct ecophysiological link to ambient concentrations of CO2 and, to a lesser extent, O-2. Cyanobacteria do not calcify at high CO2 concentrations. Experiments show that CCMs can be induced in present-day cyanobacteria at CO2 levels below similar to 10 times present atmospheric level (PAL) and that this promotes sheath calcification. We compiled a global database of cyanobacterial calcification in marine environments throughout the Ordovician (485-443 Myr ago) and compared it with modelled estimates of atmospheric CO2 and O-2. These data show that many genera of marine calcified cyanobacteria reappeared from Cambrian Series 2 or first appeared globally during the late middle to late Upper Ordovician (late Darriwilian to late Katian) in carbonate platform facies, resulting in a previously unrecognized ten-fold increase in global diversity. Such a large increase in calcification suggests widespread induction of CCM expression in cyanobacteria, consistent with sustained decline in external CO2 concentrations below similar to 10 x PAL, together with increase in dissolved O-2 level, during the late Darriwilian, Sandbian and Katian stages, similar to 460-445 Myr ago. These cyanobacterial calcification fossil proxy data provide a first order constraint on modelled estimates of atmospheric CO2 for the Ordovician. Estimated CO2 outputs from COPSE and recent GEOCARB-based models are broadly consistent with this cyanobacterial calcification proxy for the Ordovician. In view of the long history of cyanobacteria, the calcified cyanobacterial proxy offers potential to assist interpretation of CO2 deeper into geological time. (C) 2019 Elsevier B.V. All rights reserved.