| Affiliation: | 1. Geology and Geophysics, Yale University, New Haven, Connecticut;2. Earth Science, University of California, Riverside, Riverside, California;3. Microbial and Environmental Genomics, J. Craig Venter Institute, San Diego, California;4. Georgia Institute of Technology, Atlanta, Georgia;5. Earth Science, Université de Bretagne Occidentale, Brest, France;6. J. Craig Venter Institute, Rockville, Maryland;7. Geosciences, Virginia Tech, Blacksburg, Virginia;8. Florida State University, Tallahassee, Florida;9. Geology, Geological Survey of Canada, Ottawa, ON, Canada;10. School of Earth and Environmental Sciences, University of St Andrews, St Andrews, Scotland, UK;11. Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada;12. Earth Science, University of Southern Carolina, Los Angeles, California |
| Abstract: | The biogeochemical cycling of zinc (Zn) is intimately coupled with organic carbon in the ocean. Based on an extensive new sedimentary Zn isotope record across Earth's history, we provide evidence for a fundamental shift in the marine Zn cycle ~800 million years ago. We discuss a wide range of potential drivers for this transition and propose that, within available constraints, a restructuring of marine ecosystems is the most parsimonious explanation for this shift. Using a global isotope mass balance approach, we show that a change in the organic Zn/C ratio is required to account for observed Zn isotope trends through time. Given the higher affinity of eukaryotes for Zn relative to prokaryotes, we suggest that a shift toward a more eukaryote‐rich ecosystem could have provided a means of more efficiently sequestering organic‐derived Zn. Despite the much earlier appearance of eukaryotes in the microfossil record (~1700 to 1600 million years ago), our data suggest a delayed rise to ecological prominence during the Neoproterozoic, consistent with the currently accepted organic biomarker records. |
