Distribution and Potential Nitrification Rates of Aerobic Ammonia-Oxidizing Microorganisms in Surface Sediments of Mangrove in Sanya River

Abstract

The ammonia oxidation process is a rate-limiting step in nitrification. Ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) are the major drivers of ammonia oxidation. Their distribution and relative contributions to nitrification are the research highlights in the nitrogen cycle. Real-time quantitative polymerase chain reaction (qPCR) was used to study the distribution of aerobic ammonia-oxidizing microorganisms in the surface sediments of mangrove in the Sanya River, and the relative contribution rates of AOB and AOA to nitrification were calculated through the determination of the potential nitrification rates (PNR). The results showed that, in most sampling sites, the abundance of AOA amoA genes was higher than that of AOB amoA genes. The abundance of AOB was higher during the winter, whereas that of AOA was higher during the summer, and the ratio of AOA to AOB abundance was lower during the winter. The dissolved oxygen (DO) content, pH, total organic carbon (TOC) content, and nitrate concentration greatly influenced the abundance of AOB and AOA. The potential nitrification rates of AOB and AOA were both higher during the summer than during the winter, and the relative contribution rate of AOA to nitrification was higher during the winter, whereas that of AOB was higher during the summer. There were no significant correlations between the PNR and amoA genes abundance of AOB and AOA.