THE INFLUENCE OF EMERGENT MACROPHYTES ON THE ABUNDANCE AND COMMUNITY COMPOSITION OF AMMONIA OXIDIZERS

Ammonia oxidation which is both the first and a significant step in nitrogen cycling can be catalyzed by ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). In this study, the abundance and community composition of AOA and AOB in the rhizosphere sediments of two emergent macrophytes (Zizania caduciflora and Phragmites australis) were investigated in January and August in Lake Taihu to elucidate the relationship between emergent macrophytes and the abundance and diversity of AOA and AOB. The abundance of archaeal amoA gene ranged from 3.13x10(6) to 2.61x10(8) copies per gram of dry sediment, whereas the abundance of bacterial amoA gene ranged from 9.62x10(5) to 3.14x10(7) copies per gram of dry sediment. The abundance of the bacterial amoA gene was significantly positively correlated with NO3--N (P<0.05), and OM concentrations exhibited a positive correlation between the abundance of archaeal amoA gene and bacterial amoA gene (P<0.05). 94.81% of archaeal amoA sequences fell into Nitrosopumilus and Nitrosotalea clusters. For the bacterial amoA sequences, Nitrosospira lineage predominated in the sediment sample of Zizania caduciflora in January, whereas the other samples were predominant with N.oligotropha lineage. The data obtained in this study may be useful to support studies in researching the effect of emergent macrophytes on the nitrification process of lake ecosystems.