Dennis Hansell has conducted research on the biogeochemistry of major elements in the ocean for more than 30 years. His analyses have largely focused on data collected in the conduct of international projects addressing hydrographic and biogeochemical surveys of the global ocean. Questions of particular interest revolve around the role of dissolved organic matter (DOM) in the cycling of marine carbon, such as the accumulation of DOM in the surface ocean, its export to great depth with overturning circulation, its fate upon export, and its introduction to the deep ocean via sinking biogenic particles. This work has been done in all the major ocean basins; thus, the research products lend themselves to furthering understanding of the ocean as a global system. Hansell served as co-editor of the first two editions of this book. Craig Carlson is a Professor in the Department of Ecology, Evolution, and Marine Biology at the University of California, Santa Barbara. For the past three decades Carlson’s research interests have been shaped by an interdisciplinary blend of organic biogeochemistry and marine microbial ecology. His research contributions include assessing the dissolved organic matter (DOM) production, removal, and transformation processes in marine systems, providing accurate measurements of DOM inventories, determining the role of DOM export in the biological carbon pump and it’s the fate after export within the dark ocean. The overall goal of these research efforts strives to make quantitative links between microbial community dynamics and DOM biogeochemistry in the open sea. Carlson served as co-editor of the first two editions of this book.