Distribution Pattern and Diversity Maintenance Mechanism of the Denitrifier Community in Alkaline Copper Mine Drainage

Abstract

Denitrifiers have been shown to vary in abundance and diversity across the environmental gradients; however, the factors that determine the type and magnitude of the response of the denitrifier communities remain unclear. In order to reveal the effects of alkaline mine drainage (AlkMD) on the denitrifier community composition and diversity maintenance mechanism in a tailings reservoir, we examined the diversity patterns and adaptation mechanisms of different denitrifier communities in Shibahe copper tailings water in Zhongtiaoshan, China. The results showed that the -diversity of Proteobacteria and the nosZI-bearing denitrifier community in downstream seeping water (SDSW) were the highest, while those in the upstream tailings water (STW1) were the lowest. The highest nirS and nirK-bearing denitrifier community -diversity were measured in STW1, and the lowest in STW3. The community dissimilarity of the denitrifier communities was strongly correlated with environment parameters, but the factors varied in different groups. The Proteobacteria community was correlated strongly with nitrate (NO3-); the nirS and nirK-bearing denitrifier communities were correlated strongly with pH, total carbon (TC), NO3- and ammonia nitrogen (NH4+), and the nosZI-bearing denitrifier community was correlated strongly with total organic carbon (TOC), dissolved oxygen (DO), NO3-, electroconductibility (EC) and spatial distance (PCNM1). Our results indicated that environmental changes were valuable index reflecting variations in denitrifier community composition in AlkMD. Additionally, the findings in this study are helpful in understanding the relationship between the microbial community composition changes and functional adaptation in different ecosystems. IMPORTANCEMetal mine tailings pond is an important site polluted by heavy metals and nitrogen, and excess nitrogen is mainly removed by microorganisms through denitrification. Although many studies have reported that Proteobacteria is the main denitrifying bacteria, and nirS, nirK and nosZ-bearing denitrifiers are three key functional groups in denitrification process. However, less is known of their response to discharge of alkaline copper tailings wastewater (AlkMD). AlkMD exerts an adverse impact on composition and structure of denitrifying bacteria community. The change of nitrogen and carbon concentration along the flow direction of wastewater resulted in the change of denitrifying bacteria community diversity pattern, that is to say, environmental filtering force drove the denitrifier community structure in this highly polluted ecosystem.