This report presents data from analyses of seabed sediment samples collected during two Ocean Survey 20/20 voyages to the Chatham Rise and Challenger Plateau in 2007 (TAN0705 and TAN0707, respectively). Sediment samples were collected by multicorer and by pipe dredges attached to the epibenthic sled and beam trawl. Sediment grain-size, composition, microbial abundance and biomass analyses were carried out under Ministry of Fisheries project ZBD2007-01, with input from earlier OS 20/20 projects.