Elevated CO2 causes a change in microbial communities of rhizosphere and bulk soil of salt marsh system

Using TRFLP and real-time qPCR, this study aimed to investigate the way elevated CO2 (eCO2) affects bacteria, fungi, archaea, and sulfate-reducing bacteria in salt marsh systems containing halophyte Suaeda japonica. Moreover, it also aimed to evaluate the effects of eCO2 in terms of plant interaction by analyzing the rhizosphere and bulk soil separately. We observed that the gene abundance and community structures were affected by eCO2, and the rhizosphere and bulk soil communities showed a different response. The rhizospheric microbes responded to eCO2 more strongly than the bulk soil microbes. The results also showed that the sulfate-reducing bacteria (SRB) community was more sensitive to eCO2 than the general bacterial community. In addition, the findings suggested that bacteria and archaea competed severely when exposed to eCO2, which caused a dominance of bacteria over archaea or the co-presence of bacteria and archaea with a different micro-niche. Overall, eCO2 caused a strong change in the microbial community in salt marsh with halophytes, but the overall functional activity of the microbial community was unchanged and balanced by the different response patterns of the bacterial, fungal, and archaeal communities in our system.