Bacterial vertical and horizontal variability around a deep seamount in the Tropical Western Pacific Ocean

Research on bacterial communities in seamounts is still in its infancy. Spatial variability of bacterial communities was investigated around M5 seamount of the Tropical Western Pacific Ocean. Our results revealed greater variability of bacterial communities vertically than horizontally. Bacterial diversity generally increased with depths within water column and the complexity increased with the sampling depths. All stations had water mass-specific bacterial community compositions, with distinct bacterial community structure between the bottom layer (being Actinobacteria and Firmicutes-dominant) and other layers (being Alphaproteobacteria-dominant), except the deepest B2 which showed gradual transition. Major orders tended to be distributed symmetrically at bilateral sides of the seamount with more differences occurring at section B than at section A, possibly due to the westward North Equatorial Current (NEC) along section B and reverse subcurrent, as well possible upwelling. Seamount exerted certain effect on bacterial horizontal distribution in the surrounding water mainly through topography-current interaction.