Implication of Nitrifying and Denitrifying Bacteria for Nitrogen Removal in a Shallow Lake

Abstract

The relationship among reed nitrogen (N) uptake, nitrifying and denitrifying bacteria, and N content in the rhizosphere sediment was studied based on field investigation in terrestrial zone (TZ), ecotone zone (EZ), and submerged zone (SZ) of Baiyangdian Lake, the largest natural freshwater body of Northern China. The results showed that the total nitrogen (TN) content in the rhizosphere sediment decreased with increased aboveground reed TN storage, achieving the highest decrease rate of 68.6–78.6% when the aboveground reed TN storage reached its maximum in September. A positive correlation could be shown between amoA‐type nitrifier assemblages and ammonium (NH4+) content in the rhizosphere sediment. However, the correlation between nirS‐type denitrifiers and nitrate (NO3−) in the rhizosphere sediment was not significant. The amoA‐type nitrifier and nirS‐type denitrifier assemblages were significantly correlated with air temperature in each zone (p < 0.01). The quantity of amoA‐type nitrifiers in the TZ was 48.3% higher compared with the SZ, whereas the average number of nirS‐type denitrifiers in the submerged zone was twice than that in the TZ. These results imply that reed growth and environmental conditions, including air temperature and water level, are important for N removal in shallow lakes.