Bacterial and archaeal compositions and influencing factors in soils under different submergence time in a mercury-sensitive reservoir.

ABSTRACT

Soils in the water-level-fluctuating zone (WLFZ) of Three Gorges Reservoir (TGR) inundated by water for different periods of time are confirmed to have disparate characteristics to mercury (Hg), and thus it is of great significance to further investigate microbial compositions and influencing factors. The objective of this study was to compare bacterial and archaeal richness, α-diversities and compositions, as well as affecting variables, especially Hg concentrations, among soils under different submergence time-SI (inundated soil), SS (semi-inundated soil), SN(non-inundated soil) and SSe (sediment)-based on high throughput sequencing. Results showed that sediment had significantly higher bacterial and archaeal richness and α-diversities than the other soil types. Anaerolinea and Aeromonas, as well as Altiarchaeales, Nitrosoarchaeum, and Methanosarta were dominant in SSe, while sharply decreasing in the other soil types, with significant difference among groups. An unclassified genus in SCG critically predominating in SI, SS and SN, drastically reduced in SSe, with extremely significant difference among groups. Bathyarchaeota and Nitrososphaera, both dominating in SSe, decreased dramatically and almost vanished in SI and SN. All the variables except pH posed a significant positive effect on bacterial and archaeal compositions in SSe, while opposite effect in the other three soil types. MeHg and THg concentrations had relatively weaker effects on microbial compositions comparing to variables like NH4+, CEC, OM and SO42+.