Vertical distribution of microbial communities and their response to metal(loid)s along the vadose zone-aquifer sediments.

Abstract

This study attempted to demonstrate the vertical shift in bacterial, archaeal and fungal communities along the vadose zone-aquifer sediments and their respective responses to environmental factors. We collected samples from the vadose zone and three aquifer sediments along a 42·5m bore of a typical agricultural land. The results showed that the bacterial community shifted greatly with depth. The classes of Actinobacteria (19·5%) and NC10 (11·0%) were abundant in the vadose zone while Alphaproteobacteria (22·3%) and Gammaproteobacteria (20·1%) were enriched in the aquifer. Archaeal and fungal communities were relatively more homogeneous with no significant trend as a function of depth. Process analyses further indicated that selection dominated in the bacterial community, whereas stochastic processes governed archaeal and fungal communities. Moreover environment-bacteria interaction analysis showed that metal(loid)s, especially alkali metal, had a closer correlation with the bacterial community than physicochemical variables. Depth strongly affected bacterial rather than archaeal and fungal communities. Metal(loid)s prevailed over physicochemical variables in shaping the bacterial community in the vadose zone-aquifer continuum. Our study provides a new perspective on the structure of microbial communities from the vadose zone to the deep aquifers.