Effect of Dissolved Oxygen on Diversity of Ammonia-Oxidizing Microorganisms in Enrichment Culture from Estuarine Wetland Surface Sediments and Ammonia-oxidizing Rate
溶氧对富集培养的河口湿地表层沉积物氨氧化菌多样性及氨氧化速率的影响

Dissolved oxygen (DO) is one of the important environmental factors influencing the ammonia oxidation process. In order to examine the effects of DO on ammonia oxidation process and its potential mechanisms, surface sediments from Jiulong River Estuarine Wetland were collected and cultured to obtain enrichment cultures. Then the enrichment cultures were inoculated under different levels of DO, and the diversity of ammonia-oxidizing microorganisms was analyzed using PCR-DGGE technique to determine the effect of DO on the ammonia oxidation rate and the ammonia-oxidizing microorganism diversity. Results showed that the Shannon index was 2.00 and 2.05 for ammonia-oxidizing bacteria (AOB) under saturated and aerobic conditions, respectively, and the values were 2.49 (saturated) and 2.03 (aerobic) for ammonia-oxidizing archaea (AOA). However, this index was 1.76 and 1.80 for AOB under hypoxia and anaerobic condition, and 1.27 and 2.21 for AOA. Under saturated and aerobic conditions (higher DO level), the ammonia-oxidizing rates were 14.20 mg·(L·d)-1 and 13.36 mg·(L·d)-1 and the related conversation rates of NH4+-N were 93.8% and 88.2%, respectively. In comparison, under hypoxia and anaerobic conditions (lower DO level), the ammonia-oxidizing rates were 7.82 mg·(L·d)-1 and 5.66 mg·(L·d)-1 and the related conversation rates of NH4+-N were 51.7% and 37.4%, respectively. The correlation analysis showed that DO concentration was highly significantly positively correlated with the ammonia oxidation rate, and was significantly positively correlated with the AOB diversity index; DO and ammonia oxidation rate had no correlation with indices of AOA community.