Microbial communities and arsenic biogeochemistry at the outflow of an alkaline sulfide-rich hot spring

Abstract

Alkaline sulfide-rich hot springs provide a unique environment for microbial community and arsenic (As) biogeochemistry. In this study, a representative alkaline sulfide-rich hot spring, Zimeiquan in the Tengchong geothermal area, was chosen to study arsenic geochemistry and microbial community using Illumina MiSeq sequencing. Over 0.26 million 16S rRNA sequence reads were obtained from 5-paired parallel water and sediment samples along the hot springâ €™ s outflow channel. High ratios of As(V)/As Sum (total combined arsenate and arsenite concentrations) (0.59-0.78), coupled with high sulfide (up to 5.87 mg/L), were present in the hot springâ €™ s pools, which suggested As(III) oxidation occurred. Along the outflow channel, As Sum increased from 5.45 to 13.86 Î 1/4mol/L, and the combined sulfide and sulfate concentrations increased from 292.02 to 364.28 Î 1/4mol/L. These increases were primarily attributed to thioarsenic transformation. Temperature, sulfide, As and dissolved oxygen significantly shaped the microbial communities between not only the pools and downstream samples, but also water and sediment samples. Results implied that the upstream Thermocrinis was responsible for the transformation of thioarsenic to As(III) and the downstream Thermus contributed to derived As(III) oxidation. This study improves our understanding of microbially-mediated As transformation in alkaline sulfide-rich hot springs.