Seth John, Ph.D.
Associate Professor (Research)
Earth Sciences Program
Department of Earth Sciences
University of Southern California
Website | sethjohn(replace this with the @ sign)usc.edu
Project: Biological Cycling of Trace-Metals and Their Isotopes in the North Pacific
Trace metals dissolved in seawater, such as iron, zinc and cadmium, are crucial for life in the ocean. Marine organisms require metals for a wide variety of life processes, from photosynthesis and carbon assimilation to nutrient acquisition. While the importance of metals has long been known, their low concentration in seawater (parts-per-trillion levels) make analysis challenging, leading to a paucity of data on metals compared with other nutrients.
In conjunction with the SCOPE project, we will explore how trace metals influence biological cycles in the North Pacific Subtropical Gyre, and how the can be used as tracers of biological processes on local and global scales. For example, iron isotopes will be used to trace sources of iron; cadmium concentrations and isotopes will be used to quantify nutrient uptake, mixing and nitrogen fixation; and zinc and zinc isotopes will be used to quantify biological production and export. Both culture work and in situ experiments are used to study the role of metal micronutrients such as Fe on community structure and metabolism.
Seth John is an Associate Professor (Research) at the University of Southern California. Previously he was an Assistant Professor at the University of South Carolina. He received a BA in chemistry from Carleton College, followed by graduate studies in the MIT/WHOI Joint Program and a postdoc at Caltech. John studies the biogeochemical cycling of trace metals and their stable isotope ratios in the oceans. His research has included the first high-spatial resolution sections of trace metal isotopes in the ocean, as well as laboratory experiments and numerical modeling to interpret this natural data.