Variation of the sediment denitrifying bacterial community in a floodplain lake (Poyang Lake, China) during the wet, mid-dry and dry seasons

To date, seasonal dynamics of the denitrifying bacterial community in floodplain lakes is unknown. Here, we investigated the alpha diversity, abundance and composition of the sediment nirS-type denitrifying bacteria in Poyang Lake during the wet, mid-dry and dry seasons using Illumina MiSeq sequencing and quantitative polymerase chain reaction assay. The results showed that only a small part of the total operational taxonomic units (OTUs) were shared by the three seasons. OTU richness, Chao richness estimator and Shannon index exhibited higher values in the wet season than in the dry season. Some regular patterns of variation in the composition of the nirS-type denitrifying community at three classification levels (phylum, class and genus) were found among seasons. Community structures of nirS-type denitrifying bacteria were significantly different across seasons. In addition, the abundance of nirS gene showed no seasonal pattern. Total nitrogen, total phosphorous and pH were the most significant factors elucidating the compositional variation of the nirS-type denitrifying community. This study provided a new evidence for the ecological effects of seasonal water level fluctuations and improved our understanding of the nitrogen removal processes in floodplain lakes.