Dr. Jonathan P. Zehr is a Professor of Ocean Sciences at the University of California, Santa Cruz. He received his B.S in Biology from Western Washington University in 1981 and his Ph.D in Ecology from the University of California, Davis, in 1985. Dr. Zehr did postdoctoral work in nitrogen cycling at the State University of New York, Stony Brook and Brookhaven National Laboratory, and in molecular biology at New England Biolabs, Inc. in Beverly, Massachusetts. He joined the faculty of Biology at Rensselaer Polytechnic Institute in 1992. In 1999, Dr. Zehr began his current position as Professor of Ocean Sciences at the University of California, Santa Cruz. He is a Fellow of the Academy of Microbiology and the American Association for the Advancement of Sciences. His research has focused on nitrogen cycling by aquatic microorganisms, although he has publications spanning topics in microbial diversity in freshwater and hypersaline systems, organic matter metabolism, selenium metabolism in estuarine sediments, and nitrogen metabolism in oligotrophic oceans. His major focus is oceanic nitrogen fixation.Dr. Douglas G. Capone is a Professor in the Dornsife College of and William and Julie Wrigley Chair in Environmental Studies at the University of Southern California (USC). Dornsife. He received his Ph.D. in Oceanography from the Rosenstiel School of Marine and Atmospheric Sciences of the University of Miami (Fl) in 1978. He joined the faculty of the Marine Sciences Research Center of Stony Brook University (NY) in 1979 and the Center for Environmental Science of the University of Maryland in 1987. Since 1999, he has held the Wrigley Chair of Environmental Biology at the USC and served as Chair of the Department of Biological Sciences from 2008 to 2019. He is a Fellow of the American Academy of Microbiology, the American Geophysical Union and the American Association for the Advancement of Science. His research focuses on the role and importance of marine microbes in major biogeochemical cycles, particularly those of nitrogen and carbon, both from the perspective of the fundamental ecology of these process in marine ecosystems and their physical, chemical and biotic controls.