Spatial distribution of ammonia oxidizers in marine sediments of the Bohai, Yellow and East China Seas

Abstract

Ammonia oxidation, an essential process within the global nitrogen cycle, is mainly performed by ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). To date, the current knowledge on the biogeography of AOA and AOB in the ocean across a large geographic distance remains poorly known. In this study, the abundance, microbial composition, and diversity of AOA and AOB in marine sediments collected from the Bohai Sea, Yellow Sea, and East China Sea were characterized by employing quantitative PCR and Illumina Miseq sequencing of both archaeal and bacterial amoA genes. qPCR analysis demonstrated significantly higher abundances of archaeal amoA genes than those of bacterial amoA genes with AOA/AOB ratios varying from 1.59 to 292.88, suggesting a greater contribution of AOA to nitrification in the seas. Nitrosopumilus and Nitrosospira were the predominant clusters of AOA and AOB respectively in all sediment samples. The distribution pattern of both AOA and AOB communities revealed by PCoA (principal coordinate analysis) showed distinct geographic separation of sediment samples from the three seas. Correlation analysis indicated that ammonia (NH4+-N) and nitrate (NO3−-N) content were the main selective forces leading to the distinct biogeography of the two ammonia oxidizers in the ocean. The results are of great significance in improving our understanding of the contribution of AOA and AOB in the nitrogen transformation in the marine ecosystem and providing insights into the environmental factors that shape the assembly of aerobic ammonium oxidizers.