TY - JOUR T1 - Bioactive trace metals and their isotopes as paleoproductivity proxies: An assessment using GEOTRACES‐era data A1 - Horner,T.J. A1 - Little,S.H. A1 - Conway,T.M. A1 - Farmer,J.R. A1 - Hertzberg,J.E. A1 - Janssen,D.J. A1 - Lough,A.J.M. A1 - McKay,J. A1 - Tessin,A. A1 - Galer,S.J.G. A1 - Jaccard,S.L. A1 - Lacan,F. A1 - Paytan,A. A1 - Wuttig,K. A1 - Members,Geotraces–pages Biological Producti AD - NIRVANA Labs AD - Department of Marine Chemistry & Geochemistry Woods Hole Oceanographic Institution Woods Hole MA ,USA AD - Department of Earth Sciences University College London London, GBR AD - College of Marine Science University of South Florida FL, USA AD - Department of Geosciences Princeton University Princeton NJ ,USA AD - Max‐Planck Institute for Chemistry Mainz ,DEU AD - Department of Ocean Earth & Atmospheric Sciences Old Dominion University Norfolk VA ,USA AD - Institute of Geological Sciences and Oeschger Center for Climate Change Research University of Bern Bern ,CHE AD - University of Southampton National Oceanography Centre Southampton ,GBR AD - College of Earth, Ocean, and Atmospheric Sciences Oregon State University Corvallis OR, USA AD - Department of Geology Kent State University Kent OH ,USA AD - LEGOS University of Toulouse CNRS CNES, IRD, UPS Toulouse ,FRA AD - Institute of Marine Sciences University of California Santa Cruz Santa Cruz CA ,USA AD - Antarctic Climate and Ecosystems Cooperative Research Centre University of Tasmania Hobart ,AUS UR - https://archimer.ifremer.fr/doc/00702/81406/ DO - 10.1029/2020GB006814 KW - biological pump KW - marine chemistry KW - biogeochemical cycles KW - micronutrients KW - phytoplankton KW - paleoceanography N2 - 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. Y1 - 2021/11 PB - American Geophysical Union (AGU) JF - Global Biogeochemical Cycles SN - 0886-6236 VL - 35 IS - 11 ID - 81406 ER -