Early evolution of environments and metabolism: insights from nitrogen, selenium and sulfur isotopes Eva E. Stüeken A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Washington 2014 Reading committee: Roger Buick, Chair John A. Baross David C. Catling Program authorized to offer degree: Earth & Space Sciences ©Copyright 2014 Eva E. Stüeken 2 Acknowledgments My work and I have been funded by various agencies over the years, including the UW Royalty Research Fund, the National Science Foundation, the UW Astrobiology Program, the Earth & Space Science Department, and a GSA Graduate Student Research grant. I owe special thanks to Vikki Meadows for funding parts of my field work. I further thank Andy Schauer, Kyle Samek, Joy Laydback, Scott Kuehner and Dave McDougall for technical support, and Julien Foriel for training me and making me a better geochemist during the first two years. I thank Zach Adam for introducing me to the Belt Supergroup in western Montana and for helping me plan my sample collection. Additional samples were provided by Roger Buick, Simon Poulton, Gerald Zieg, Bradley Guy, Boswell Wing, Ariel Anbar, Andrew Knoll, Linda Kah, Hans Machel, Shane Schopefer and Isabel Montanez. I also thank Charlotte Schreiber for establishing contacts to some of her colleagues and for sharing thoughts on sedimentology and environmental evolution. I thank John Baross, David Catling and David Stahl for serving on my advisory committee, especially John for many inspiring conversations over lunch about life as such and its origins in particular. I want to thank Rika Anderson, Zoë Harold, Sanjoy Som, Marcela Ewert- Sarmiento, Billy Brazelton, Anthony Adler and Clara Fuchsman for friendship, dinners and board game nights, and my family for support over the long distance. But none of this would have been possible – and it certainly would have ended a lot sooner – without support and encouragement from the best PhD advisor I could have asked for. Roger, I thank you for being an academic father in every sense of the word. 3 University of Washington Abstract Early evolution of environments and metabolism: insights from nitrogen, selenium and sulfur isotopes Eva Elisabeth Stueeken Chair of the Supervisory Committee: Dr. Roger Buick Department of Earth & Space Sciences The evolution of planet Earth and its biosphere are tightly linked through global biogeochemical cycles, and this dissertation seeks to explore this linkage during the Precambrian with new strategies and geochemical techniques. The first chapter is the result of a group project in which we propose that multiple environments and processes were involved in prebiotic chemistry. We conclude that the origin of life can be more plausibly explained if the various building blocks of living cells slowly emerged from global geochemical cycles. In the second part of my thesis (Chapters 2-3), I explore how microorganisms exploited and modified these cycles, in particular the global sulfur cycle. Statistical analyses of sulfur concentrations and isotopic ratios in marine mudrocks support an early Archean origin of microbial sulfate reduction and late Archean enhancement of biological pyrite oxidation on land, leading to increasing fluxes of sulfate and other nutrients to the ocean. In the third part (Chapters 4-7), I further test this hypothesis through analyses of selenium isotopes and abundances. After establishing a new 4 analytical technique, I show that selenium was mobilized by oxidative weathering in the late Archean, concurrently with sulfur. Because of selenium’s high redox potential, these results confirm the antiquity of oxygenic photosynthesis. A compilation of selenium data through time further indicates oxygenation of the deep ocean in the Neoproterozoic or mid-Paleozoic, which may have facilitated the rise of metazoans. The late Permian mass extinction, however, was apparently not directly linked to an episode of ocean anoxia. The third part of this work (Chapters 8-10) focuses on nitrogen isotopes as a proxy for nitrogen speciation in the water column. Results show that biological nitrogen fixation using Mo-nitrogenase dates back to at least the mid-Archean and was the dominant nitrogen source at that time. Marine nitrate concentrations were also low in the mid-Proterozoic, which may have restricted the radiation of eukaryotic life. Lastly, I use nitrogen isotopes in lacustrine sediments as a proxy for alkalinity and show that alkaline lakes may have been common on Archean continents, making them potentially important environments for the origin and early evolution of life. 5 Table of Contents Introduction ................................................................................................................................... 9 Chapter 1: Did life originate from a global chemical reactor? ............................................... 12 Abstract ..................................................................................................................................... 12 1.1. Introduction ........................................................................................................................ 13 1.2. Prerequisites for the origin of life ...................................................................................... 16 1.3. Hadean micro-environments and their potential role in the origin of life ......................... 23 1.4. Global transport and concentration processes on the Hadean Earth .................................. 39 1.5. Merging bioinformatics with geochemistry ....................................................................... 48 1.6. Future research directions .................................................................................................. 52 1.7. Conclusion ......................................................................................................................... 55 Tables ........................................................................................................................................ 58 Figures....................................................................................................................................... 61 References ................................................................................................................................. 67 Appendix to Chapter 1 .............................................................................................................. 82 Chapter 2: Contributions to Late Archaean sulphur cycling by life on land ....................... 88 Abstract ..................................................................................................................................... 88 2.1. Introduction ........................................................................................................................ 89 2.2. Method ............................................................................................................................... 89 2.3. Results ................................................................................................................................ 91 2.4. Discussion and conclusion ................................................................................................. 91 Tables ........................................................................................................................................ 96 Figures....................................................................................................................................... 97 References ............................................................................................................................... 100 Appendix to Chapter 2 ............................................................................................................ 102 Chapter 3: Evolution of the Archean sulfur cycle revealed by quadruple sulfur isotopes 135 Abstract ................................................................................................................................... 135 3.1. Introduction ...................................................................................................................... 136 3.2. Methods............................................................................................................................ 138 3.3. Results .............................................................................................................................. 139 3.4. Discussion ........................................................................................................................ 140 3.5. Conclusion ....................................................................................................................... 146 Tables ...................................................................................................................................... 149 Figures..................................................................................................................................... 150 References ............................................................................................................................... 154 Appendix to Chapter 3 ............................................................................................................ 157 Chapter 4: Selenium isotope analysis of organic-rich shales: advances in sample preparation and isobaric interference correction .................................................................