Impacts Of Jingjiang Channel Remediation Project On The Water Bacterial Communities

Objective: The Jingjiang Channel Remediation Project including reinforcement,guarding,and slot filling,etc.spanned from Changmen River,Yichang to Xiongjiazhou,Yueyang,with a length of 280.5 kilometers.Different types of projects might have different impacts on riverine ecosystems due to their disturbances to the sediments and water.So far,there were few studies focused on the impact of the channel project on aquatic bacterial communities.The impacts of the Jingjiang River Channel Remediation Project on the diversities and structures of the water bacterial communities were analyzed.And the bacteria associated with the implementation of the project were screened out to provide data from the perspective of aquatic bacterial ecology for evaluating the environmental impacts of the Jingjiang River Channel Remediation Project.Methods: During three water periods of low-water period at 2013,high-water period at 2014 and low-water period at 2014,water samples were collected from eight river segments of the remediation project.Each river segment was divided into the construction section,the control section,and the abatement section.Three sampling points were set in these sections.These samples were then filtered through acetate glass fiber membranes with 0.45 μm diameters.The genomic DNA of the bacterial communities were extracted,and the 16 S r DNA libraries were established and sequenced.The analysis is carried out on the following three levels: Ⅰ)all water samples from the eight river segments collected from 2013 to 2015 were considered into analysis;Ⅱ)all samples from Yaojian segment were considered in the analysis so that river segments as the most main influence factor was controlled;Ⅲ)all the water samples were grouped into three water periods including low-water period at 2013,high-water period at 2014 and low-water period at 2014 so that the water period as the key factor was controlled.In the above three research levels,the water bacterial community diversities and structures are analyzed,the differences of the water bacterial community diversities and structures between the construction and nonconstruction groups were compared,and a series of construction-related bacterial taxa were identified.Furthermore,the impacts of water physicochemical parameters and heavy metals on the water bacterial community were analyzed.Results: Ⅰ)The analysis on all water samples showed that the river segments,sampling section,year,and water period were the main factors significantly influenced the water bacterial community structures(P<0.05).There was no significant difference in the alpha diversities and structures of the water bacterial communities between the construction and non-construction groups.A total of 14 Amplicon Sequence Variants(ASV)with significant differences between groups were identified by LEf Se,mainly belonging to Rhizobiales and Actinomycetales.Ⅱ)After controlling the key factor of the river segments,the guarding project and the reinforcement guarding project implemented at Yaojian segment.The Chao1 index,ACE index,Shannon index and Observed features in the construction group were significantly lower than those in the non-construction group(P<0.05).The bacterial community structures of the two groups were also found to have significant differences through the PCo A analysis(P<0.05).It is shown that the guarding project and the reinforcement guarding project significantly affect the water bacterial community α-diversity and structure.A total of 13 ASVs were identified by LEf Se,mainly belonging to Ellin6075,JG30-KF-CM45,Rhizobiales,Exiguobacterium,Thermomonas,Sphingobacterium,and Arthrobacter etc.The analysis on the dynamics of the bacterial communities over time showed that the trend on PCo AAxis 1 and the relative abundance of Proteobacteria at the construction section was approximately the same as that at the abatement section,but it was different from that at the control section.It indicated that the construction had obvious impacts on bacterial community structures which could not disappear in a short time along a short distance.The trend on the relative abundance of Firmicutes at the construction section was different from that at the abatement section and the control section,which showed that the impact of construction on Firmicutes is more significant than that on Proteobacteria.Ⅲ)The Faith pd of the water bacterial community at the same water period was significantly different between the construction and non-construction groups during the high-water period and low-water period at 2014,indicating that the evolutionary diversity of the two groups was significantly different after controlling the influencing factor of water period.The bacterial community structure during the low-water period at 2014 showed significant differences among groups(P<0.05).A total of 30 ASVs were identified by LEf Se,mainly belonging to Rhizobiales,Bacillales,JG30-KF-CM45,and Actinomycetales.Conclusion: The main factors that had significant impacts on the water bacterial community structures at the Jingjiang River in this study were the river segment,sampling section,year,and water period(P<0.05).It was found that the guarding project and the reinforcement guarding project significantly reduced the alpha diversity and changed bacterial community structures at Yaojian segment.A total of 13 ASVs associated with the guarding and reinforcement guarding projects were initially identified.The ASV of f＿Rhizobiaceae＿c7cf was significantly increased in the construction group,while the remaining 12 ASVs such as g＿Methylobacterium＿0496 were significantly decreased in the construction group.It was revealed that construction significantly altered the water bacterial community structures during the low-water period at 2014.A total of 11construction-related ASVs were initially identified.Six ASVs including g＿Chelativorans＿2100 were significantly increased in the construction group,while five ASVs such as g＿Bacillus＿6223 were significantly decreased in the construction group.