Effects of Spartina alterniflora invasion on Kandelia candel rhizospheric bacterial community as determined by high-throughput sequencing analysis

The biomass and diversity of mangroves suffer a significant decline when S. alterniflora invades in China. The objective of this study was to examine the effects of S. alterniflora invasion on Kandelia candel rhizospheric bacterial community and to explore the control factors of the soil function. In this study, the high-throughput sequencing method was applied to assess the composition and diversity of rhizospheric bacterial community in mangrove community (MC), S. alterniflora community (SC), and mangrove-S. alterniflora community (MS). Relationships were also analyzed between the relative abundances of bacterial communities and soil nutrients. The results revealed that S. alterniflora invasion resulted in a significant decline of rhizospheric nutrients. The S. alterniflora invades and exacerbated the microecological imbalance in the rhizospheric soils of MS, and markedly decreased the soil bacterial community diversity. The change trends of five alpha diversity indexes followed the order of SC > MC > MS. At the phylum level, S. alterniflora invasion resulted in a significant increase in the relative abundance of Proteobacteria and Euryarchaeota, but a significant decrease of Firmicutes and Nitrospirae. At the genus level, S. alterniflora invasion resulted in obvious differences in rhizospheric bacterial community of MS. Both the correlation and redundancy analyses suggested that the soil nutrient content was the main soil factor affecting the relative abundance of bacterial communities, and the soil nutrients play an important role in the shifts of soil bacterial community diversity. This study documented the degradation of soil nutrients and the significant variations of rhizospheric bacterial community in MS under S. alterniflora invasion.