Antarctic Circumpolar Current creates a boundary limiting the meridional dispersal of bacteria in the Southern Ocean

Impact statement As the world's largest ocean current in terms of volume transport, the Antarctic Circumpolar Current (ACC) significantly affects the movement of heat and water in the Southern Ocean. However, the impact of the ACC on the biogeographic distribution of marine bacteria is unknown. Here, by sampling and investigating the bacterial communities from surface seawater samples surrounding Antarctica and across the ACC region, we show that the ACC acts as a barrier limiting the dispersal of bacteria through it. This dispersal limitation, which reduces the communication between bacteria near Antarctica and foreign bacteria, will possibly be impacted by future climate change.