Marine phytoplankton do half of all photosynthesis on Earth and directly influence global biogeochemical cycles and climate, yet how they will respond to future global change is unknown. As an oceanographer who takes an integrative Earth system approach to research, Kate Mackey addresses this knowledge gap by studying the biogeochemical activity of phytoplankton over a range of scales, from the cellular level up to global biogeographical distributions of species and strains. She uses culture studies to characterize biochemical processes on a mechanistic level, and fieldwork to verify lab findings, identify the range of responses from natural populations and determine their implications in nature. Mackey is the Clare Boothe Luce Assistant Professor of Earth System Science at the University of California, Irvine. She leads a large, dynamic lab of talented graduate and undergraduate students who work together and share a passion for research, teaching, science outreach and promoting diversity in academia. Mackey was named a Sloan Research Fellow in ocean sciences in 2017 and was a recipient of the inaugural Marion Milligan Mason Award for Women in the Chemical Sciences by the American Association for the Advancement of Science (AAAS) in 2015. Mackey completed postdoctoral research at the Woods Hole Oceanographic Institution and the Marine Biological Laboratory in Cape Cod Massachusetts, where she was a National Science Foundation Postdoctoral Fellow. She received her M.S. and Ph.D. in environmental engineering from Stanford University in 2004 and 2010, respectively, and held graduate research fellowships from both the National Science Foundation and the Department of Energy. She earned two B.S. degrees in biological engineering and plant science in 2002 at the University of Maryland at College Park.