Plankton populations have lived in the oceans for hundreds of millions of years, performing essential functions within marine ecosystems. This book explores emerging and current topics in marine ecosystem plankton research, focusing on pelagic diversity, functioning, and productivity from a multidisciplinary structural and functional view. It also examines the context of environmental stressors and global Climate Change Research and Policy. The book represents a contribution from a team of researchers from several regions of the world with a common mission to enhance readers' understanding of current ocean science and marine biology while pointing towards future directions.