Spatial distribution and diversity of microbial community in large-scale constructed wetland of the Liao River Conservation Area

Microbial communities play a key role in wetland water purification and nitrogen cycling. The spatial distribution and diversity of total bacteria in large-scale constructed wetland were investigated by polymerase chain reaction-denaturing gradient gel electrophoresis. The abundance of nitrogen related functional bacteria were measured by real-time PCR using specific primers. The results showed that the diversity of total bacterial community decreased from the inlet zone (Shannon-Wiener index, H' = 3.471) to the outlet zone (H' = 2.566), so did the species richness and evenness. The dominant bacteria of the wetland were Proteobacteria, Acidobacteria and Bacilli. The abundance of amoA gene was higher than those of another two functional genes. There was significant correlation between the abundance of amoA gene and pH (r = 0.852), DO (r = -0.595), NH4+ (r = 0.595) and NO3- (r = 0.726) concentrations. The abundance of nosZ gene correlated with the DOC concentration (r = -0.614). The ratio of amoA/Nitrospira showed significant correlation with NH4+ concentration (r = 0.641), while the ratios of amoA/nosZ (r = -0.801) and Nitrospia/nosZ (r = -0.610) could reflect the NO2- concentrations. Therefore, the three ratios of nitrogen related functional genes may serve as new biological indicators for wetland condition assessment.