Characteristics of bacterial community structure in the nearshore sediments of Longjiang River and the environmental impact factors

Abstract:

[Background] Heavy metal pollution in Longjiang River has been a great concern since the “dam collapse” in 2012. [Objective] To reveal the bacterial community structure in nearshore sediments of heavy metal-polluted rivers and the environmental influencing factors. [Methods] With the high-throughput sequencing method (Illumina MiSeq PE300), we investigated the bacterial community characteristics in nearshore sediments of Longjiang River and the correlation with environmental factors. [Results] The average content of As, Cd, and Zn in the nearshore sediments of Longjiang River was 25.06, 3.20 and 205.36 mg/kg, 1.22, 11.97 and 2.72 folds of the soil environmental background values of Guangxi, respectively. The C/N ratio ranged from 3.66 to 13.15, with the average of 10.55, indicating that the organic nitrogen was mineralized in the sediments. The dominant bacterial phyla were Chloroflexi (12.16%–35.36%), Proteobacteria (7.69%–30.85%), Acidobacteria(8.56%–22.48%), Bacteroidetes (5.26%–30.41%), Desulfurobacteria (1.14%–10.65%), and Actinobacteria (1.55%–4.17%), and the dominant classes were Anaerolineae (8.92%–30.04%), Gammaproteobacteria (5.10%–24.98%), Bacteroidetes (1.54%–26.95%), Acidobacteria (1.69%–9.40%), Vicinamibacteria (1.23%–9.09%), and Alphaproteobacteria (2.42%–6.67%). Correlation analysis showed that the abundance of bacterial community in sediments was significantly correlated with NH₄⁺-N and pH, and ACE and Chao 1 indexes of bacterial community were negatively correlated with NH₄⁺-N (P<0.05). [Conclusion] The abundance and diversity of bacterial community in sediments were mainly affected by NH₄⁺-N and pH, and the dominant communities were related to the biogeochemical cycle of carbon, nitrogen, phosphorus and sulfur. The sediments might be the home to some pollution indicator microorganisms and pathogenic microorganisms.