Effects of drying-rewetting alternating on nitrogen-related microbial functional communities in bioretention systems

Abstract:

[Objective] This study aims to explore the effect of environmental factors on nitrogen-related microbial functional community structure of bioretention systems under the condition of drying-rewetting alternation.[Methods] Soil samples were collected from spatial distribution (planting layer, submerged layer) in vegetated and un-vegetated bioretention systems after drying and rewetting. The amoA and nirS functional genes were used as molecular marker. The diversity and community structure of nitrifying and denitrifying bacteria in different soil samples were studied by high-throughput sequencing technology named Illumina MiSeq PE300. Canonical correlation analysis (CCA) and redundancy analysis (RDA) were performed to assess the relationship between nitrogen-related microbial functional community structure and environmental factors was analyzed.[Results] The functional genes of microbial populations showed significant spatial differences. Nitrogen-related functional bacteria in the planting layer were more abundant and diverse than which in the submerged layer. However, the differences in proportion of operational taxonomic units (OTUs) between the two functional genes in planting layer and submerged layer were increased by rewetting. The results from the community composition analysis of nitrogen-related functional microbes showed that the dominant phylum of amoA-nitrifying and nirS-denitrifying bacteria were the Proteobacteria in all the soil samples. The root system of plants had no significant effect on the diversity index of nitrogen-related functional microbes, but in the plant system layer, the denitrifying bacteria species (at the genus level) were more than that in the submerged layer, and the opposite trend were showed in the plant-free system. The analysis of CCA and RDA showed that soil spatial distribution was the most important environmental factor on the distribution of nitrifying and denitrifying microbial communities.[Conclusion] The nitrogen-related functional microbial community in bioretention system under drying and rewetting alternation was controlled by the soil spatial distribution, water content and plant roots. However, the underlying reasons still await further investigation.