Lakes in arid regions are experiencing mercury pollution via air deposition and surface runoff, posing a threat to ecosystem safety and human health. Salinity and organic matter input could influence the mercury cycle and composition of bacterial communities in the sediment.

Associate Professor SONG Wenjuan from the Environmental Pollution and Ecological Remediation Laboratory, Xinjiang Institute of Ecology and Geography (XIEG) of the Chinese Academy of Sciences, and her collaborators investigated the effects of salinity and algae biomass as an important organic matter on the genes involved in the mercury cycle under mercury contamination.

The researchers took the lake sediments and lake water bodies in arid areas as the research objects, and built a microcosm system.

They used qPCR and high-throughput sequencing technologies to study the abundance of mercury reductase gene (merA) and mercury methylation gene (hgcA) as well as the diversity of microbial composition.

The results showed that bacteria, not archaea, played a key role in mercury reduction and methylation in sediments. High levels of mercury would reduce the abundance of merA and hgcA, and increase the relative abundance of mercury methylating microorganisms.

Researchers also found that the influence of salinity and algal biomass on mercury cycle genes depended on the gene type and concentration. Higher algal biomass input could increase the abundance of merA, reduce the abundance of hgcA, and lead to an increase in specific bacterial communities related to the mercury cycle, thereby increasing the abundance of bacteria involved in the decomposition of organic matter.

The study was published in Environmental Pollution on Dec. 1.