microbial communities in long-term e-waste contaminated river sediments

The release of toxic organic pollutants and heavy metals by primitive electronic waste (e-waste) processing to waterways has raised significant concerns, but little is known about their potential ecological effects on aquatic biota especially microorganisms. We characterized the microbial community composition and diversity in sediments sampled along two rivers consistently polluted by e-waste, and examined how community functions respond to the complex combined pollution. High throughput 16S rRNA sequencing showed that Proteobacteria (particularly Deltaproteobacteria) dominated the sediment microbial assemblages followed by Bacteroidetes, Acidobacteria, Chloroflexi, and Firmicutes. PICRUSt metagenome inference provided an initial insight into the metabolic potentials of these e-waste affected communities, with genes encoding key enzymes (including dioxygenase, dehydrogenase, aldolase, decarboxylase, hydroxylase and hydrolase) in organic pollutants-degradation pathways largely harbored by some of the dominant genera (such as Sulfuricurvum, Thiobacillus and Burkholderia) detected in situ. Statistical analyses revealed that toxic organic compounds contributed more to the observed variations in sediment microbial community structure and function (24.68% and 8.89%, respectively) than heavy metals (12.18% and 4.68%), and BaP, available lead and EC were the key contributors. Given the ecological significance of microbes in sediments, long-term e-waste pollution has the potential to alter nutrient cycling and contribute to functional perturbation of freshwater systems.