Seasonal variations of ammonia-oxidizing archaeal and bacterial communities in floodplain lake sediments

Abstract

Ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) are key participants in the nitrogen cycle in freshwater ecosystems. However, the seasonal dynamics of AOA and AOB communities in floodplain lakes are unclear. Here, on the basis of the high-throughput sequencing and quantitative polymerase chain reaction (PCR) of the ammonia monooxygenase (amoA) gene, we investigated the diversity, abundance, and community structure of sediment AOA and AOB in wet, mid-dry, and dry seasons in Poyang Lake, the largest floodplain lake in China. The results revealed that the AOA and AOB communities were subject to substantial seasonal variations. Specifically, the three seasons shared only 14.4–28.3% and 17.4–25.2% of the total operational taxonomic units (OTUs) for each AOA and AOB community, respectively. Permutational multivariate analysis of variance (PERMANOVA) and principal component analysis (PCA) further indicated that the community structure of both AOA and AOB differed significantly among seasons. In addition, the season exerted a marked influence on the alpha diversity of AOA but not that of AOB. The season did not significantly impact the abundance of either AOA or AOB. Total nitrogen (TN) and total phosphorus (TP) were significantly related to the AOA community structure in the lake sediments, while organic matter (OM) was significantly associated with the AOB community composition. Our research demonstrates that there are seasonal variations in AOA and AOB communities in floodplain lake sediments, highlighting the impact of seasonal water level fluctuations on the nitrification process within such habitats.