Department of Marine Microbiology and Biogeochemistry, NIOZ Royal Netherlands Institute for Sea Research, and Utrecht University, PO Box 59, 1790AB, Den Burg (Texel), The Netherlands.
University of Bristol, School of Earth Sciences, Wills Memorial Building, Queens Road, Bristol, BS8 1RJ, UK.
Sci Rep. 2020 Jun 29;10(1):10508. doi: 10.1038/s41598-020-67483-8.
Understanding long-term trends in atmospheric concentrations of carbon dioxide (pCO) has become increasingly relevant as modern concentrations surpass recent historic trends. One method for estimating past pCO, the stable carbon isotopic fractionation associated with photosynthesis (Ɛ) has shown promise over the past several decades, in particular using species-specific biomarker lipids such as alkenones. Recently, the Ɛ of more general biomarker lipids, organic compounds derived from a multitude of species, have been applied to generate longer-spanning, more ubiquitous records than those of alkenones but the sensitivity of this proxy to changes in pCO has not been constrained in modern settings. Here, we test Ɛ using a variety of general biomarkers along a transect taken from a naturally occurring marine CO seep in Levante Bay of the Aeolian island of Vulcano in Italy. The studied general biomarkers, loliolide, cholesterol, and phytol, all show increasing depletion in C over the transect from the control site towards the seep, suggesting that CO exerts a strong control on isotopic fractionation in natural phytoplankton communities. The strongest shift in fractionation was seen in phytol, and pCO estimates derived from phytol confirm the utility of this biomarker as a proxy for pCO reconstruction.
理解大气二氧化碳（pCO）浓度的长期趋势变得越来越重要，因为现代浓度超过了最近的历史趋势。过去几十年来，一种估计过去 pCO 的方法——与光合作用相关的稳定碳同位素分馏（Ɛ），特别是使用特定于物种的生物标志物脂质（如烯酮），显示出了很大的潜力。最近，更通用的生物标志物脂质（源自多种物种的有机化合物）的Ɛ 已被应用于生成比烯酮更长、更普遍的记录，但这种示踪剂对现代环境中 pCO 变化的敏感性尚未得到限制。在这里，我们使用从意大利武尔卡诺岛埃奥利群岛的利万特湾自然发生的海洋 CO 渗漏处采集的一条测线上的各种通用生物标志物来测试Ɛ。所研究的通用生物标志物，如 lolilide、胆固醇和植醇，在从对照点到渗漏点的整个测线上都显示出 C 的逐渐消耗，这表明 CO 对自然浮游植物群落中的同位素分馏具有很强的控制作用。分馏的最强变化发生在植醇中，而植醇衍生的 pCO 估计值证实了该生物标志物作为 pCO 重建示踪剂的实用性。
