This report presents diversity metrics of benthic organisms between and within the Chatham Rise and the Challenger Plateau areas sampled during Ocean Survey 20/20 voyages to the area in March-April and May-June 2007. The Ocean Survey 20/20 voyages represent the most comprehensive sampling initiative in these areas to date and aimed to describe patterns of benthic habitat and biological diversity across extensive areas of the EEZ. Objective 6 (addressed in this report) was devised to provide information about the biodiversity of the Chatham Rise and Challenger Plateau; compare many of the different indices of biodiversity available; and analyse how these vary across a range of spatial scales and taxonomic resolutions.