In this study we characterise the microbial biogeography of the South Pacific Gyre across three depth categories over a > 2000 km transect.

Oligotrophic subtropical gyres are microbial dominated systems. The South Pacific Gyre is the largest subtropical gyre and represents the largest continuous biome on Earth. In this study, we used 16S rRNA gene amplicon sequencing to reveal the microbial biogeography of the region. Microbial communities were homogeneous across a longitudinal transect of over 2000 km in the surface waters of the region, but were significantly more diverse and variable at the deep chlorophyll maximum.