Seasonal Variation of Ammonia-Oxidizing Microorganisms in Freshwater Ecosystems of Jinshan Lake, an Urban Lake in Zhenjiang, Jiangsu Province, China.

Ammonia oxidation, which is the first and rate-limiting step in nitrification, is thought to be performed by ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). Understanding the ecological distribution characteristics of ammonia-oxidizing bacteria and ammonia-oxidizing archaea is essential to elucidate the roles of ammonia-oxidizing microorganisms in freshwater ecosystems. This study aimed to determining the abundance, diversity and community composition of ammonia-oxidizing bacteria and ammonia-oxidizing archaea and their seasonal dynamics by using PCR primers designed to specifically target the ammonia monooxygenase α-subunit (amoA) genes of AOA and AOB and q-PCR, in freshwater ecosystems of Jinshan Lake, an urban lake in Zhenjiang, Jiangsu Province, China. Results showed: (1) AOA were not detected in spring and summer; AOB were not detected in spring; and AOA were found to be generally higher than AOB in both autumn and winter; (2) The AOA abundance was significantly correlated with the pH, temperature, DO, NH₄-N, and NO₂-N in the water column. The AOB abundance was significantly correlated with the NH₄-N. AOB had a higher diversity and richness of amoA genes than AOA. Both of H and S_Chao1 values of AOB were significantly correlated with the temperature, DO, and NH₄-N. No significant correlations were observed between the H and S_Chao1 values of AOA and environmental variables; (3) Among the 70 archaeal amoA sequences retrieved, 58.57% and 41.43% fell within the Nitrosopumilus and Nitrososphaera clusters, respectively. The 169 bacterial amoA gene sequences obtained in this study were grouped with known AOB sequences in the Nitrosomonas and Nitrosospiragenera, which occupied 89.35% and 10.65% of the AOB group, respectively. These results indicate that ammonia-oxidizing microorganisms may play an important role in the ecology of urban lakes.

Keywords: ammonia-oxidizing archaea, ammonia-oxidizing bacteria, urban lake, amoA, qPCR