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Bioactive trace metals and their isotopes as paleoproductivity proxies: an assessment using GEOTRACES-Era data


Horner, TJ and Little, SH and Conway, TM and Farmer, JR and Hertzberg, JE and Janssen, DJ and Lough, AJM and McKay, JL and Tessin, A and Galer, SJG and Jaccard, SL and Lacan, F and Paytan, A and Wuttig, K, Bioactive trace metals and their isotopes as paleoproductivity proxies: an assessment using GEOTRACES-Era data, Global Biogeochemical Cycles, 35, (11) Article e2020GB006814. ISSN 0886-6236 (2021) [Refereed Article]


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Copyright 2021 The Authors. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0)

DOI: doi:10.1029/2020GB006814


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.

Item Details

Item Type:Refereed Article
Keywords:biological pump, marine chemistry, biogeochemical cycles, micronutrients, phytoplankton, paleoceanography
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical oceanography
Objective Division:Environmental Management
Objective Group:Other environmental management
Objective Field:Other environmental management not elsewhere classified
UTAS Author:Wuttig, K (Dr Kathrin Wuttig)
ID Code:152325
Year Published:2021
Web of Science® Times Cited:7
Deposited By:Ecology and Biodiversity
Deposited On:2022-08-17
Last Modified:2022-09-13
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