Diversity and community structure of ammonia oxidizers in a marsh wetland of the northeast China

As an interface of terrestrial and aquatic ecosystems, wetland is a hotspot of the global nitrogen cycle. Ammonia oxidation is an essential part of the nitrogen cycle and is conducted by ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). Based on the amoA gene, the distribution and genetic diversity of AOA and AOB in the marsh wetland soil with different soil layers and vegetation had been investigated. The result showed that both soil layer and vegetation significantly influenced the diversity and abundance of AOA and AOB. AOB dominated numerically in all soil samples. The average bacterial amoA gene copies (2.62 × 109 copies/g dry soil) was 100-fold higher than the average archaeal amoA gene copies. In the soil sample under the Phragmites australis, the highest archaeal amoA gene was in depth 20–40 cm, whereas the bacterial amoA gene was more abundant in depth 0–20 cm. For the soil under Calamagrostis angustifolia, the highest archaeal and bacterial amoA gene were both detected in depth 0–20 cm. The dominated AOA was cluster AII, which was most related to the amoA gene found in aquatic habitat. Cluster BI accounted for 59.1% of bacterial amoA gene and it was related to the amoA gene found in the terrestrial habitat. CCA analysis revealed that NO3− was the main factor for AOA and AOB community structure in the P. australis soil. However, NO2− and NH4+ were important factors for AOA and AOB in the soil under C. angustifolia.