Bacterial Community Diversity In Arctic Midre Lovénbreen Glacier Region And Its Downstream Bay Area

Studying relationship between changes of microbial community and geochemical properties of environment is an important branch of ecosystem research.The Arctic is one of the regions most affected by global climate change,warming twice as fast as the earth’s average.Climate change leads to the intensification of glacial meltwater,resulting in the change of nutrient concentration and geochemical properties of water and soil,and thus the change of bacterial community structure.The change of salinity of meltwater runoff in the estuary has a significant impact on the bacteria in the water,leading to the change of bacterial diversity and functional gene diversity in the nearshore marine ecosystem.In this study,glacier meltwater samples from eight sites and soil samples from three sites in the Midre Lovénbreen glacier region of Svalbard were selected as the research objects.By high-throughput sequencing of V3-V4 region of 16S rDNA of the samples,the differences in bacterial community structure caused by changes of geochemical properties of glacier meltwater and soil were analyzed.Then,metagenomic sequencing technology was used to analyze the structure and function of bacterial community in water samples from three sites with different salinity in the estuary of the bay area,and the effects of salinity changes on bacterial diversity and metabolic function genes were discussed.The results suggest that there was a great difference in bacterial diversity in the upstream and downstream of meltwater of Midre Lovénbreen glacial runoff in the Arctic:In the upstream of meltwater,Proteobacteria,Actinobacteria and Firmicutes were the dominant bacterial phyla,while Bacteroidetes and Cyanobacteria were dominant in the downstream.Compared with glacial meltwater,the bacterial community structure in glacial soil was more complex,and most of the dominant bacteria belonged to βProteobacteria.Actinobacteria in glacial soil migrated selectively to meltwater through contact between them.In the study of correlation between geochemical properties and bacterial community diversity,NO3--N and NO2--N were significantly correlated with bacterial community in glacial meltwater and soil,respectively(P<0.05).WGCNA network analysis also showed that NO3--N and NO2--N had the strongest correlation with dominant core bacteria in glacier area.The bacterial metagenomic analysis of the glacial meltwater estuary suggest that the composition of bacterial community in the inshore bay changed greatly due to the salinity difference.For example,the abundance of Rhodobacteraceae,Pseudoalteromonadaceae,Flavobacteriaceae and Vibrionaceae was relative high in the estuary,while the abundance of Colwelliaceae,Chromatiaceae and Alteromonadaceae was higher inside the bay.Pearson correlation analysis suggest that the abundance of genes related to nitrogen and sulfur cycle was significantly affected by salinity,and both of them were negatively correlated with salinity(P<0.05).In conclusion,it was found that there was a significant correlation between the diversity of bacterial community and NO3--N and NO2--N in the glacial meltwater and soil.The experimental results showed that there was a strong correlation between the bacterial community diversity and the nitrogen cycle in the glacial runoff area,while in the estuary of the bay area,the genes related to nitrogen and sulfur cycle changed greatly with the salinity changing.The input of glacial meltwater not only affects the glacial ecosystem,but also affects the marine ecosystem.