3.1 Overall diversity of the sedimental microbial communities
A total of 29 sedimental samples in the Beibu Gulf were collected and subjected to total DNA extraction. For each sample, the V3-V4 region of the 16S rRNA gene were amplified and sequenced, targeting the bacterial communities in the Beibu Gulf sediment. After data processing including quality filtering, chimera removal and rarefaction, 8,007 merged sequences per sample were retained. These sequences were then clustered into 13,073 bacterial ASVs (Supplementary Table 1). By applying 0.01% relative abundance as the cutoff, 13,001 bacterial ASVs (51.19% in relative abundance) were classified as rare taxa, and 72 ASVs (48.81% in relative abundance) as abundant taxa.
Taxonomically, the bacterial communities were dominated byGamma-Proteobacteria (31.39%), Delta-Proteobacteria(20.01%), Acidobacteria (10.57%), Bacteroidetes(9.62%), and Actinobacteria (3.69%) (Fig. 1a). On average, each sediment sample was found with 299 ASVs, of which 65 were abundant and 235 were rare (Fig. 1b). Further analysis suggested that abundant and rare subcommunities differed dramatically in Pielou’s evenness and Shannon-Wiener diversity indices (Supplementary Figure 2), as well as within community similarity (Fig. 1c). Such results suggested that the abundant and rare subcommunities tended to differ in spatial scaling patterns as well as local community assembly mechanisms.