Alterations of bacterial and archaeal communities by freshwater input in coastal wetlands of the Yellow River Delta, China

Freshwater input has been widely used for wetland restoration. However, the consequences of freshwater input on bacteria and archaea remain poorly understood. Here, we examined the bacterial and archaeal diversity and community structure through high-throughput sequencing of 16S rRNA genes. Soil samples at a depth of 0-10 cm were collected in various kinds of Phragmites australis wetlands (flooded freshwater-restored (FW), nonflooding (PW) and tidal flooding (TW)) to investigate how the diversity and community structure of bacteria and archaea responded to freshwater input. The alpha-diversity metrics revealed that the bacterial richness and diversity in FW did not significantly differ from those in PW and TW (p 0.05). However, archaeal richness and diversity was higher in FW than in PW (p < 0.05). Firmicutes and Crenarchaeota constituted the predominant bacterial and archaeal phyla in FW, respectively, whereas Proteobacteria (bacteria) and Thaumarchaeota (archaea) exhibited the highest relative abundance in both PW and TW. The community structure of bacteria and archaea in TW differed from those in FW and PW, as revealed by beta diversity metrics and the analysis of similarities. Moreover, linear discriminant analysis effect size indicated that the largest number of discriminating bacterial and archaeal taxa was found in TW. The Mantel test and Spearman correlation analysis showed that environmental variables (i.e. salinity, soil organic matter and soil texture) influenced the bacterial and archaeal diversity and community structure. And soil salinity parameters played a predominant role in shaping bacterial and archaeal communities. Overall, our findings indicated that freshwater input led to variations in bacterial and archaeal communities.