Comparison of Microbial Community Composition and Diversity in Native Coastal Wetlands and Wetlands that Have Undergone Long-Term Agricultural Reclamation

Land conversion from wetlands to farmlands is pervasive in coastal areas. However, comparisons of soil microbial community structure between native wetlands and long-term reclaimed farmlands have received less attention. We investigated this issue in two Phragmities austrialis wetlands with different hydrological regimes (permanent and seasonally inundated) based on phospholipid fatty acid (PLFA) analysis and 16S rRNA pyrosequencing. In the permanent wetland, the farmland had higher contents of fungal (+331 %), bacterial (+60 %), actinomycetic (+50 %), and total (+81 %) PLFAs compared with the native wetland. In the drained wetland, the farmland had higher fungal (+982 %) PLFAs contents, but lower contents of bacterial (−78 %), actinomycetic (−98 %) and total (−54 %) PLFAs compared with the native wetland. Bacteria and actinomycetes were dependent on wetland hydrological conditions, while fungi were sensitive to other alterations. Fungal/bacterial-PLFAs ratios were higher in farmlands than wetlands. The relative abundances of Proteobacteria, Firmicutes and Bacteroidetes were higher in farmlands than wetlands. Compared with PLFA, 16S rRNA differentiated fewer differences in bacterial community composition. Farmlands had lower bacterial Shannon-Wiener index compared with the permanent wetland, but not for the seasonal wetland. In conclusion, native wetlands and associated farmlands have differences in microbial community structure and diversity, which are mainly dependent on hydrological and nutrient conditions.