This book arises from a workshop on the application of network analysis to ecological flow networks. The purpose is to develop a new tool for comparison of ecosystems, paying particular attention to marine ecosystems. After a review of the methods and theory, data from a variety of marine habitats are analyzed and compared. Readers are shown how to calculate such properties as cycling index, average path length, flow diversity, indices of ecosystem growth and development and the origins and fates of particular flows. This is a highly original contribution to the growing field of ecosystem theory, in which attention is paid to the properties of the total, functioning ecosystem, rather than to the properties of individual organisms. New insights are provided into the workings of marine systems.