| Acid Mine Drainage(AMD)is a type of wastewater with high acidity and high concentration of heavy metal and sulfate.It is a specific biogeochemical condition originating from the oxidation of ores,which has become a global environmental and health threat.Long-term irrigation of cultivated land with AMD has inevitably ratcheted up soil acidity and resulted in the enrichment of toxic metals and sulfate from contaminated rivers,thereby reducing the large scale of arable land and causing the appearance of environmental disaster zones.Microbial communities play a critical role in nutrient elements cycles and ecosystem functions.Understanding the interaction between microbes and important geochemical factors on different scales has also become a hot issue.The biogeochemical cycles driven by microbes have become the noval strategies for issues of environmental restoration.In this study,the Dabaoshan Fe-sulfate metal mining area in northern Guangdong Province was selected as the research area,we collected soil samples from paddy soils under AMD contaminated along the Hengshi River Basin.High-throughput sequencing techniqueswas applied to characterize the microbial communities'structural composition and functional characteristics in paddy soils under AMD irrigation.The correlation between soil environmental chemical factors and microbial community were analyzed to explore the key role of environmental factors in microbial community changes.In addition,the response of microbial community structure in paddy soil after the irrigation water pH elevated was also detected.Furthermore,the molecular ecological network method was used to study the change of interaction between microbial groups in paddy soil along Hengshi River Basin.The research results are as follows:(1)AMD pollution caused the microbial community structure in paddy soil dominated by Acidobacteria and Crenarchaeota,and these groups were significantly correlated with AMD influenced environmental factors such as pH and heavy metals(Cu,Pb and Zn).The most contaminated site was Shangba Village(S3),which has microbial community dominated by genus Candidatus Solibacter and Candidatus Koribacter.PICRUSt predicts functional genes showed that AMD contamination causes differential distribution of C/N-related metabolic pathway genes,so that the microbial community structure of contaminated samples can better adapt to low pH environments.(2)The Acidobacteria also dominated along Shangba paddy soil profile,and the abundance in the root soil samples even reaches 33.3%of the whole soil bacterial community consisting with their spatial dominance.However,the Acidobacteria group in different layers of soil showed different characteristics.Gp1 and Gp3 were mainly distributed in the surface layer(SA,S1 and S2);the deep layer samples(S4-S9)mainly dominated by Gp2;Composition,while the S3 sample consists mainly of Gp1,Gp2 and Gp3.The sulfate concentration is generally higher than that of the previously studied paddy soil,thus the abundance of sulfate-reducing bacteria functional gene dsrB abundance in soil reached1.92×10~9 copies/g dry soil,which was higher than that of other similar environments.The abundance of soil SRB in rice fields decreased along the water inlet to the water outlet,and gradually decreased from the surface layer to the deep layer.The most dominant genus in the whole SRB community is Desulfobacca,indicating that the genus occupies an important position in the sulfur cycle of AMD irrigated paddy soil.(3)The microbial community characteristics were significantly different after the pH of irrigation water change within one year.The diversity of microbial communities was significantly increased.The results of?diversity showed that the response mechanism of bacterial and archaeal community structure were significantly different.The community spatial differences decreased during irrigation water pH increased and the bacterial community was more sensitive than the archaeal community under environmental disturbance.After the irrigation water pH elevated,the microbial community maintains a dominant microbial group similar to the low pH at the time of contamination,and these core dominant species in the community still maintain a similar correlation with the pollution,indicating that the core microbial community has strong adaptability in the soil ecology.The stability of the system persists over a wide pH range.The stability of this structure may suggest that the regulation of paddy soil function can only achieved by regulating the stable core microbiome.(4)After the irrigation water pH elevated,the complexity of the bacterial network rises sharply and then falls back,but in general,it is more complicated than the paddy soil network under AMD irrigation.Although Acidobacteria still plays a key role as a linker,but the position has decreased during irrigation water elevation.The important functional group Proteobacteria has assumed an important modular hub in the bacterial network after the pH increased.In additon,it can be concluded that the low-abundance microbial group plays an important role in the ecological network of the whole microbe.In the archaeal network,the proportion of the competition between the soil archaea species gradually decreases,and the cooperation between the archaeal species increases.In general,the complexity of archaeal communities is small,and the ability of archaea to resist changes in external environmental conditions is better.Compared with the bacterial community,the archaeal communities in the soil exist in a more segregated network,and the degree of communication and niche sharing between different types of archaea are lower.In summary,this study can help people further understand how indigenous microbes in paddy soil respond to AMD contaminated and how microbial communities paddy soil change during AMD governance,providing new functional microbiological information of further bioremediation strategy for AMD contaminated remediation. |
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