Environmental drivers affecting the bacterial community of intertidal sediments in the Yellow Sea

Intertidal flats, as transition zones where terrestrial and marine ecosystems meet, provide unique environments and play an important role in marine ecosystems. In particular, the environmental characteristics of tidal marshes show are different than those of bare flats, especially in the rhizosphere. However, unlike the rhizosphere in terrestrial ecosystems, the rhizosphere of plants in tidal marsh areas and the associated microbial community have been the focus of very little research. Thus, this study investigated the diversity and variation in bacterial communities in the rhizosphere of a Phragmites australis and Suaeda japonica and along the sediment depths. High-throughput sequencing was performed by amplifying the 16S rRNA gene of environmental DNA extracted from sediment cores, and indicator species were identified with respect to the vegetation type and sediment depth. The most abundant phylum was Proteobacteria, followed by Chloroflexi, Bacteroidetes, Acidobacteria, and Firmicutes. In general, the results indicated that not only vegetation type and sediment depth themselves but also their interaction resulted in significant differences among the bacterial communities. The envfit results revealed that the environmental variables of sediment, such as mud content, organic matter, total organic carbon, and total nitrogen, had significant effects on the bacterial community structure. The indicator species varied depending on the vegetation type and sediment depth, showing significant correlations with certain selected environmental variables, but were fundamentally related to the rhizosphere. Overall, this study revealed the key factors that determine the bacterial community structure in tidal marshes and the indicator species according to vegetation type in the little studied rhizosphere of the intertidal ecosystem.