The origin of carbon isotope vital effects in coccolith calcite.
The origin of carbon isotope vital effects in coccolith calcite.
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DOI：
10.1038/ncomms14511
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发表时间：
2017-03-06
影响因子：
16.6
通讯作者：
Rickaby RE
中科院分区：
文献类型：
--
作者：
McClelland HL;Bruggeman J;Hermoso M;Rickaby RE
方解石微化石被广泛用于研究地球地质历史中的气候和海洋学。颗石体是由一组单细胞海洋表层藻类（称为颗石藻）产生的容易保存的方解石片，自晚三叠世以来已成为海洋沉积物的重要组成部分。然而，与有孔虫的外壳不同，它们的浮游动物对应物，球珊瑚在古重建中仍然没有得到充分利用。在细胞内的化学和同位素微环境中，颗石方解石表现出大的和神秘的偏离非生物成因方解石的同位素组成，被称为重要的影响。在这里，我们表明，钙化固碳比决定是否颗石方解石是同位素重或轻比非生物成因方解石，和偏差的大小是由碳利用的程度。我们讨论的理论潜力，目前的局限性，颗石为基础的CO2古压力，最终可能会促进无处不在的和地质广泛的沉积档案的使用。由于未知的生命效应，使其同位素特征复杂化，因此在古重建中通常未充分使用球石。在这里，作者开发了一个通过体内实验校准的碳同位素通量的细胞模型，并阐明了破坏颗石效用的重要影响。
Calcite microfossils are widely used to study climate and oceanography in Earth's geological past. Coccoliths, readily preserved calcite plates produced by a group of single-celled surface-ocean dwelling algae called coccolithophores, have formed a significant fraction of marine sediments since the Late Triassic. However, unlike the shells of foraminifera, their zooplankton counterparts, coccoliths remain underused in palaeo-reconstructions. Precipitated in an intracellular chemical and isotopic microenvironment, coccolith calcite exhibits large and enigmatic departures from the isotopic composition of abiogenic calcite, known as vital effects. Here we show that the calcification to carbon fixation ratio determines whether coccolith calcite is isotopically heavier or lighter than abiogenic calcite, and that the size of the deviation is determined by the degree of carbon utilization. We discuss the theoretical potential for, and current limitations of, coccolith-based CO2 paleobarometry, that may eventually facilitate use of the ubiquitous and geologically extensive sedimentary archive. Coccoliths are generally underused in palaeo-reconstructions due to unknown vital effects, which complicate their isotopic signatures. Here, the authors develop a cellular model of carbon isotopic fluxes calibrated by in vivo experiments and shed light on the vital effects that undermine coccolith utility.