Heterogeneity of the horizontal environment drives community assemblages and species coexistence of prokaryotic communities in cold seep sediments

Abstract. Microbes in cold seep sediments play important roles in controlling methane filtration and the global geochemical cycle, but little is known about microbial distribution and community assembly in the horizontal sediment profile. This study conducted a comprehensive investigation of prokaryotic community diversity in sediments from different habitats in a cold seep ecosystem of the South China Sea. Compared to other sites, the prokaryotic community in the methane seep site showed a lower α-diversity. Halobacterota was dominant in methane seep site, while higher abundances of Chloroflexi and Asgardarchaeota were observed in the fauna sites. The assembly process of the bacterial community in the methane seep site was mainly a stochastic process, while the archaeal community was mainly formed by a deterministic process. The prokaryotic community in fauna sites was influenced by both stochastic and deterministic processes. The heterogeneity of the horizontal environment such as the content of CH4, Ba2+, total inorganic carbon, and SO42− influenced prokaryotic community diversity and drove the community assembly processes. Additionally, bacterial species coexisted more closely in methane seep site than in other sites, but archaea did the opposite. Overall, this study revealed how prokaryotes build communities in different cold seep habitats.