Decrease in Microbial Diversity Along a Pollution Gradient in Citarum River Sediment

Abstract

Pollution of water resources is a major risk to human health and water quality throughout the world. Here, we studied the effect of river pollution on the microbial community composition in the Citarum River Basin, West Java, Indonesia. Sediment was collected at six sampling points along a gradient of pollution, from the pristine source of the river to the heavily polluted downstream site in the densely populated urban area of Bandung. After DNA extraction, microbial diversity and potential for nitrogen cycling were analyzed based on 16S rRNA gene amplicon sequencing and metagenomics. Comparing the pristine sediment to the polluted site showed a lower microbial diversity and higher dominance of anaerobic processes than at the polluted site. The most dominant phylum within the Bacteria were the Proteobacteria, which shifted from Beta- and Deltaproteobacteria in the pristine site to Alpha- and Gammaproteobacteria in the polluted sediment. With pollution Actinobacteria, Bacteroidetes, and Firmicutes increased in relative abundance. Relative high abundance of Soil Crenarchaeotic group was found in all sample sites, whilst the methanogenic archaea became more abundant with increased pollution and anaerobicity. The study of the nitrogen cycling potential revealed that ammonium oxidation and denitrification appeared to be abundant processes in the pristine site, whereas ammonification seemed to be more important in the polluted site. Increased water treatment would restore water quality and microbial diversity in Citarum river sediments.