The biodiversity of many ecosystems is under threat and although seas cover the majority of our planet’s surface, far less is known about the biodiversity of marine environments than that of terrestrial systems. It is also not clear whether many of the patterns known to occur on land also occur in the sea. Until we have a firmer idea of the diversity of a wide range of marine habitats and what controls it, we have little hope of conserving biodiversity, or determining the impact of human activities such as mariculture, fishing, dumping of waste and pollution. This book brings together key studies from the deep sea and open ocean, to tropical shores and polar regions to consider how comparable the patterns and processes underlying diversity are in these different ecosystems. Marine Biodiversity will be a major resource for all those interested in biodiversity and its conservation.