Groundwater Microbial Diversity And Its Response To The Environment In Several Typical Areas Of China

Groundwater microbial is an important part of underground biogeochemical cycle.Due to unsustainable human activities,groundwater resources in China have suffered serious damage.The structure and functional diversity of groundwater microbiome can be used as an important biological indicator in groundwater environment.However,up to now,most of the studies have focused on the microbial community within a certain region,and few have studied the microbial community on a larger spatial scale across regions.Therefore,in this paper,based on 16S r DNA high-throughput sequencing technology,the salt-freshwater mixing zone of Longkou,the groundwater of Cele oasis and the water of the hyporheic zone in the middle reaches of the Yangtze River were as the research object for study the characteristics of microbial community structure diversity,and the microbial response to environmental factors.The differences of microbial diversity and functional characteristics in different study areas were compared.The main conclusions in this paper are as follows.（1）Proteobacteria were the dominant microflora in the Longkou study area.At the order level,Rhodobacterales is dominant in seawater and Burkholderiales is dominant in groundwater.TOC,T,Ca²⁺,ORP,HCO₃^-,DO and NO₃^-had the greatest influence on microbial community structure.（2）The microbial diversity of the brackish water group in Cele oasis was higher than that of the fresh water group.At the phylum level,Proteobacteris,Bacteroidota and Firmicutes had higher abundance.p H,TOC,Ca²⁺and NO₃^-had significant effects on microbial community structure.（3）There were significant differences in microbial community structure between the river,the hyporheic zone and the groundwater in the study area of the middle reaches of the Yangtze River.Proteobacteria,Cyanobacteria,Chloroflexi,Bacteroidota and Actinobacteriota are the groups with high abundance at the phylum level.EC,DO,p H,ORP,T and TOC were the environmental factors that had a great influence on the microbial community structure.（4）A comparative analysis of the three study areas showed that there were significant differences in microbial diversity between the groundwater of Longkou salt-freshwater mixing zone and Cele oasis with the hyporheic zone of the middle reaches of the Yangtze River（P<0.001）,but there was no significant difference between the groundwater of Longkou salt-freshwater mixing zone and Cele oasis.The values of Shannon index,Ace index and Heip index in the hyporheic zone are much higher than those in the salt-freshwater mixing zone and Cele Oasis.The structure of groundwater microbial communities in the salt-freshwater mixing zone of Longkou and Cele oasis is similar at the phylum level and class level,and Proteobacteria and Bacteroidota are the most abundant phyla.There were differences in microbial community function among the three study areas.The metabolic pathways significantly enriched in the salt-freshwater mixing zone of Longkou include Xenobiotics biodegradation and metabolism,Membrane transport,and Amino acid metabolism.Cell motility was significantly enriched in the groundwater of Cele oasis.The Global and overviewmaps and Translation are significantly enriched in the hyporheic zone of the middle reaches of the Yangtze River.