Plant Growth Modifications Due to Coastal Embankments Affect Soil Bacterial and Archaeal Communities Over the Growing Season in Salt Marshes of Eastern China

Aims: Although the influences of coastal embankments on physicochemical soil properties and carbon (C) and nitrogen (N) cycling have been widely studied, the mechanisms of their effects on soil microbial ecologies remain poorly understood. Thus, the aim of this study was to investigate variations in the diversity and composition of soil bacterial and archaeal communities between natural and embanked saltmarshes, as well as the determinants that drive these variations. Methods: 16S rRNA gene sequence analysis was performed to assess the impacts of embankments on the bacterial and archaeal communities of native Suaeda salsa , Phragmites australis , and invasive Spartina alterniflora saltmarshes on the east coast of China. Results: Embankments were found to significantly decrease the microbial diversity of the S. alterniflora salt marsh, while they increased the OTU richness of the P. australis salt marsh. Embankments modified the compositions of soil bacterial and archaeal communities in both the S. alterniflora and P. australis salt marshes. However, variations in the microbial diversity, richness, and community compositions between the native and embanked S. salsa salt marshes were insignificant. Conclusions: These results were possibly because the embankment significantly altered soil nutrient substrate levels (e.g., soil organic C and N) by variations in plant residues and physiochemical soil properties in S. alterniflora and P. australis saltmarshes, whereas the embankment had no observable changes in the soil nutrient substrate and the plant residue in S. salsa saltmarsh. This study also elucidated the effects of coastal embankments on biogeochemical cycles, and highlighted their potential hazards to ecosystems.