Bioactive Trace Metals and Their Isotopes as Paleoproductivity Proxies: An Assessment Using GEOTRACES‐Era Data
Bioactive Trace Metals and Their Isotopes as Paleoproductivity Proxies: An Assessment Using GEOTRACES‐Era Data
复制标题
生物活性微量金属及其同位素作为古生产力指标：使用 GEOTRACES Era 数据进行评估
DOI：
10.1029/2020gb006814
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发表时间：
2021
影响因子：
5.2
通讯作者：
Galer, S. J. G.
中科院分区：
文献类型：
--
作者：
Horner, T. J.;Little, S. H.;Conway, T. M.;Farmer, J. R.;Hertzberg, J. E.;Janssen, D. J.;Lough, A. J. M.;McKay, J. L.;Tessin, A.;Galer, S. J. G.
浮游植物的生产力和出口通过一系列称为生物泵的过程，以颗粒有机碳的形式封存了大量的大气二氧化碳。限制生物泵过去的运行方式对于了解过去大气二氧化碳浓度和地球气候历史非常重要。然而，重建生物泵的历史需要代理。由于与生物过程密切相关，几种生物活性微量金属及其同位素是过去浮游植物生产力的潜在代表，包括铁、锌、铜、镉、钼、钡、镍、铬和银。在这里，我们基于 GEOTRACES 时代的数据集回顾了这九种金属及其同位素的海洋分布、驱动过程和沉积档案。我们对每个同位素系统的整体成熟度进行评估，作为诊断过去海洋生产力的各个方面的代理，并确定未来研究的优先事项。这项评估表明，镉、钡、镍和铬同位素最有希望作为古生产力的示踪剂，而铁、锌、铜和钼则不然。对白银的了解太少，无法做出自信的决定。有趣的是，对生产力最不敏感的痕量金属可用于跟踪海洋化学的其他方面，例如营养物来源、颗粒清除、有机络合和海洋氧化还原状态。这些互补的敏感性为结合多个代理的观点提供了新的机会，最终将能够描绘出海洋古生产力、生物地球化学循环和地球气候历史的更完整的图景。
Phytoplankton productivity and export sequester climatically significant quantities of atmospheric carbon dioxide as particulate organic carbon through a suite of processes termed the biological pump. Constraining how the biological pump operated in the past is important for understanding past atmospheric carbon dioxide concentrations and Earth's climate history. However, reconstructing the history of the biological pump requires proxies. Due to their intimate association with biological processes, several bioactive trace metals and their isotopes are potential proxies for past phytoplankton productivity, including iron, zinc, copper, cadmium, molybdenum, barium, nickel, chromium, and silver. Here, we review the oceanic distributions, driving processes, and depositional archives for these nine metals and their isotopes based on GEOTRACES‐era datasets. We offer an assessment of the overall maturity of each isotope system to serve as a proxy for diagnosing aspects of past ocean productivity and identify priorities for future research. This assessment reveals that cadmium, barium, nickel, and chromium isotopes offer the most promise as tracers of paleoproductivity, whereas iron, zinc, copper, and molybdenum do not. Too little is known about silver to make a confident determination. Intriguingly, the trace metals that are least sensitive to productivity may be used to track other aspects of ocean chemistry, such as nutrient sources, particle scavenging, organic complexation, and ocean redox state. These complementary sensitivities suggest new opportunities for combining perspectives from multiple proxies that will ultimately enable painting a more complete picture of marine paleoproductivity, biogeochemical cycles, and Earth's climate history.