Biogeographic patterns and community assembly mechanisms of bacterial community in the upper seawater of seamounts and non-seamounts in the Eastern Indian Ocean

Seamounts are widespread underwater topographic features in the ocean that exert an influential role in shaping the microbial biogeographic distribution. Nevertheless, research on the differences in microbial biogeographic distribution between seamount and non-seamount upper water column is still lacking, particularly in the Indian Ocean where studies are limited. In the present study, a total of 45 seawater samples were collected from the water column (5-200 m) of seamounts (HS) and non-seamounts (E87 transect) regions in the Eastern Indian Ocean (EIO) for the analysis of microbial biogeographic patterns and community assembly processes. The results indicated that bacterial community diversity did not differ significantly between the HS and E87 transect regions; however, the community composition was significantly different. Additionally, bacterial community diversity, composition, as well as structure were more affected by depth than by region. Community diversity tended to increase with depth in E87 transect region, while it tended to decrease in HS region. A distance decay analysis also demonstrated that bacterial communities were more influenced by environmental and depth distances than geographic distances. In the assembly of bacterial communities on HS and E87 transect regions, as well as at different depths, stochastic processes, particularly dispersal limitation, were found to be predominant. These findings enhance our comprehension of bacterial community characteristics in the upper seawater of seamounts and non-seamounts regions in the EIO and offer insights into the assembly processes shaping microbial communities at varying depths.