How did shifts in ocean trace metal chemistry direct the course of evolution? This is the driving question of my PhD research. To have any chance of reconstructing the past, we first need to understand the present. I focus on Ni, a bioessential metal that is incorporated into 7 enzymes that regulate the C, N, and O cycles. Organisms such as foraminifera, phytoplankton, and methanogens rely on Ni because of its incorporation into urease, Ni-super oxide dismutase, and methyl-coenzyme M reductase. Identifying the main controls of ocean [Ni] would also mean to identify the regulators of these key marine organisms. What maintains the concentration of Ni in the modern ocean and, therefore, these important organisms?

To date, the modeled marine Ni budget is woefully out of balance; sink fluxes are estimated to be two times greater than the sources. If this model accurately represented the modern ocean, ocean [Ni] would be rapidly depleting. There is no evidence for such a scenario, so the model is likely incorrect. If inaccurate flux estimates are causing this discrepancy, we can reassess them with a 3rd variable, isotopes. With [Ni], flux, and δ60/58Ni, we can reconstrain the flux estimates. However, the major known sinks are isotopically heavier than the sources, meaning there is an isotope imbalance as well. There must be a missing isotopically heavy source or light sink. I aim to resolve the Ni isotope imbalance by adding this missing piece. My dissertation research focuses on robustly measuring the Ni isotopic compositions of lesser studied Ni reservoirs. Through my research, I hope to identify the main controllers of marine [Ni] and provide a foundation for the modern marine Ni cycle to ultimately determine the evolution of the marine Ni cycle over time.