Appraisal of sedimentary alkenones for the quantitative reconstruction of phytoplankton biomass
Appraisal of sedimentary alkenones for the quantitative reconstruction of phytoplankton biomass
复制标题
评估沉积烯酮以定量重建浮游植物生物量
DOI：
10.1073/pnas.2014787118
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
A. Rosell‐Melé
中科院分区：
文献类型：
--
作者：
M. Raja;A. Rosell‐Melé
生物标志物替代物，即烯酮，通常用于重建过去的初级生产力。然而，它们的价值一直受到质疑，因为它们被认为是由成岩过程控制的，并且往往限于对碳循环进行定性推断。事实上，大多数代用品尚未在全球范围内利用海洋地球化学数据进行评估。在这里，我们使用遥感和地球化学数据相结合，提供一个基于空间的全球尺度的校准，显示使用烯酮来量化过去的海面叶绿素a浓度，最终可以用来定量推断过去的原始生产力在古记录。这种校准为利用实地数据澄清海洋碳循环在气候变率中的相对作用铺平了道路，并测试了海洋地球化学模型。海洋初级生产力（PP）是全球海洋碳循环的驱动因素。它在过去的气候重建依赖于地球化学代理，不被认为是提供一个明确的信号。这些往往是基于水柱通量的生物成分沉积物（有机碳，生物蛋白石，生物标志物），虽然其他因素比生产力被假定为控制沉积内容的组件，和他们的流量是相关的出口产品埋在沉积物中的部分。此外，大多数通量代理尚未进行全球评估。在这里，我们评估了一个代理量化过去的浮游植物生物量相关的C37烯酮的浓度在全球套件的核心顶部沉积物与海表面叶绿素a（SSchla）的估计在过去的20年。SSchla是计算浮游植物生物量的核心指标，与PP直接相关。我们发现，沉积烯酮的全球空间分布主要与SSchla，而不是成岩因素，如氧气浓度在底部沃茨，这挑战了以前的假设上的作用，保存沉积有机化合物的驱动浓度。此外，我们的研究结果表明，全球碳出口到沉积物的速度不受区域限制，烯酮生产商在全球出口埋藏在海底的碳中发挥主导作用。这项研究表明，使用沉积烯酮估计过去的浮游植物生物量，这反过来又可以用来推断过去的PP在全球海洋的潜力。
Significance Biomarker proxies, namely alkenones, are commonly used to reconstruct past primary productivity. However, their value has been questioned as they are posited to be controlled by diagenetic processes and often limited to draw qualitative inferences on the carbon cycle. In fact, most proxies have not been globally appraised with ocean biogeochemical data. Here, we use a combination of remote sensing and geochemical data to provide a spatial-based global scale calibration that shows the use of alkenones to quantify past sea surface chlorophyll-a concentration, which ultimately can be used to infer quantitatively past primary productivity in paleorecords. This calibration paves the way to clarify the relative role of the marine carbon cycle in climate variability using field data, and tests biogeochemical models. Marine primary productivity (PP) is the driving factor in the global marine carbon cycle. Its reconstruction in past climates relies on biogeochemical proxies that are not considered to provide an unequivocal signal. These are often based on the water column flux of biogenic components to sediments (organic carbon, biogenic opal, biomarkers), although other factors than productivity are posited to control the sedimentary contents of the components, and their flux is related to the fraction of export production buried in sediments. Moreover, most flux proxies have not been globally appraised. Here, we assess a proxy to quantify past phytoplankton biomass by correlating the concentration of C37 alkenones in a global suite of core-top sediments with sea surface chlorophyll-a (SSchla) estimates over the last 20 y. SSchla is the central metric to calculate phytoplankton biomass and is directly related to PP. We show that the global spatial distribution of sedimentary alkenones is primarily correlated to SSchla rather than diagenetic factors such as the oxygen concentration in bottom waters, which challenges previous assumptions on the role of preservation on driving concentrations of sedimentary organic compounds. Moreover, our results suggest that the rate of global carbon export to sediments is not regionally constrained, and that alkenones producers play a dominant role in the global export of carbon buried in the seafloor. This study shows the potential of using sedimentary alkenones to estimate past phytoplankton biomass, which in turn can be used to infer past PP in the global ocean.
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影响因子：
4.9
作者：
Dutkiewicz S
通讯作者：
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影响因子：
5.2
作者：
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