Mercury is a global pollutant, and mercury emissions from anthropogenic sources account for about 30% of global atmospheric mercury emissions each year. Methylmercury (MeHg) converted from inorganic mercury can bioaccumulate through the food chain, posing a health risk to humans. Microbial activities play a key role in the mercury biogeochemical cycle.
Lakes in arid areas are threatened by salinization. The decay of algal biofilm is an important supplement of organic matter in sediments. Studying the effects of salinity and algal biomass on the diversity of sedimentary microbial communities and abundance of mercury cycle genes under mercury pollution is of great significance for understanding the biogeochemical cycle of mercury in lake sediments in arid areas.
Associate Professor Song Wenjuan from the Environmental Pollution and Ecological Remediation Laboratory of Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences took the lake sediments and lake water bodies in arid areas as the research objects, and built a microcosm system. They use qPCR and high-throughput sequencing technologies were applied to study the abundance of mercury reductase gene (merA) and mercury methylation gene (hgcA) and diversity of microbial composition. Studies have found that bacteria, not archaea, play a key role in mercury reduction and methylation in sediments. High levels of mercury will reduce the abundance of merA and hgcA, and increase the relative abundance of mercury methylating microorganisms (e.g., Ruminococcaceae, Bacteroidaceaceae and Veillonellaceae).
Researchers also find that the influence of salinity and algal biomass on mercury cycle genes depends on the gene type and concentration. Higher algal biomass input can 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 research results were published in Environmental Pollution, entitled "Effect of salinity and algae biomass on mercury cycling genes and bacterial communities in sediments under mercury contamination: Implications of the mercury cycle in arid region".
Article link: https://doi.org/10.1016/j.envpol.2020.116141
The absolute abundance of bacterial merA and hgcA genes in the sediment under different mercury concentrations.
Contact: LIU Jie, Xinjiang Institute of Ecology and Geography