Abstract
Our knowledge of the deep-sea fauna around Christmas Island and Cocos (Keeling) Islands in the central-eastern Indian Ocean was very limited. In 2021 and 2022, two voyages of discovery on the RV Investigator sampled benthic deep-sea habitats in the region. Sixty-seven benthic macrofaunal samples were obtained from 22 seamounts, the two island groups and the surrounding abyssal plain, ranging in depth from 94 to 5431 m. The collected material was identified to 1059 taxonomic units by taxonomists. Of these, only 495 (47%) were identified to a described species, another 149 (14%) were new species, and the remainder required additional taxonomic work to determine whether they were new or previously described. Decapods and fishes provided the most species, but ophiuroids were the most abundant taxa overall. Faunal community analyses were predominantly structured by depth, with geographic location being important within depth bands. There was a continual turnover of species from shallow to abyssal depths, particularly in the upper 1500 m of water. Seafloor habitats shallower than 1000 m are rare in the eastern Indian Ocean and form important conservation assets.