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. How the biological pump operated in the past is therefore 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 elements that are least sensitive to productivity may be used to trace 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.

中文翻译：

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具有生物活性的痕量金属及其同位素作为古生产力的代理人：使用GEOTRACES时代的数据进行的评估

通过一系列称为生物泵的过程，浮游植物的生产力和出口固存的气候中大量的大气二氧化碳以颗粒有机碳的形式存在。因此，过去生物泵的运行方式对于理解过去的大气中二氧化碳浓度和地球的气候历史非常重要。然而，重建生物泵的历史需要代理。由于它们与生物过程密切相关，因此多种生物活性痕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，我们根据GEOTRACES时代的数据集回顾了这9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，以作为诊断过去海洋生产力方面的指标，并确定未来研究的重点。该评估表明，镉，钡，镍和铬同位素最有希望成为古生产力的示踪剂，而铁，锌，铜和钼则没有。对银知之甚少，无法做出自信的决定。有趣的是，对生产力最不敏感的元素可用于追踪海洋化学的其他方面，例如营养源，清除颗粒，有机络合和海洋氧化还原状态。这些互补的敏感性为组合来自多个代理的观点提供了新的机会，这些观点最终将使人们能够更完整地描绘海洋古生产力，