Acknowledgements -- Foreword -- Introduction -- The importance of marine biodiversity -- Key features -- Hierarchical components -- The impacts of human activities on marine biodiversity -- The strategic values of research -- Status and trends -- How many marine species are there? -- Taxonomic records -- Cryptic species -- The DNA barcode -- The drive to identify new species -- The "taxonomic impediment" -- Species under pressure -- Extinct species -- Endangered species -- Ecosystems under pressure: the deep sea -- Spatial patterning of characteristics -- Temporal patterns -- Conceptualising biodiversity -- Conceptual frameworks for relationships between biodiversity and human societies -- Choice of model framework -- Measuring biodiversity -- Biodiversity as a macroscopic descriptor in the European Union Marine Strategy Framework Directive (MSFD) -- Drivers of changes in biodiversity and its uses -- Environmental drivers: a working framework -- Integrated scenarios and policies -- Policies and decision support -- Developing scenarios -- Quantitative methods, models and integrated assessment -- Research needs -- The framework: environmental research -- Naturalistic dimensions -- Human dimensions of research -- Developing modelling: a summarising approach -- Sources -- References -- Databases -- Abbreviations and acronyms -- Group of experts.