Seasonal changes in peryphytic microbial metabolism determining mercury methylation in a tropical wetland

• Published in: The Science of the total environment 2018-06, Vol.627, p.1345-1352
• Main Authors: Lázaro, Wilkinson L., Díez, Sergi, da Silva, Carolina J., Ignácio, Áurea R.A., Guimarães, Jean R.D.
• Format: Article
• Language: English
• Subjects: Amazon; Flood pulse; Methanogenic; Periphyton; Radiotracer
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2018.01.186

Mercury (Hg) methylation, a key process in the biogeochemical cycle of Hg, is mainly attributed to sulfate-reducing bacteria and methanogenic Archaea. However, environmental regulation by these groups has not yet been ascertained in tropical environments, especially in respect to the seasonal flood flooding. This work evaluated the variation of net methylmercury production potential in relation to biological characteristics of the periphyton, environmental factors, and flood pulse seasons. Our results indicate that there is a seasonal change between metabolic groups as main Hg methylators, sulfate-reducing bacteria in the dry season and methanogenic Archaea in the flood season. In addition, there was a positive relationship between dissolved organic carbon (DOC), phosphorus, cyanobacteria biovolume, and periphytic Hg methylation potential. These results shed a new light on MeHg production plasticity, mediated by landscape and flood pulses in tropical wetlands, as well as on ecological relationships within the periphyton. [Display omitted] •Net methylmercury production in tropical wetlands is related to different factors.•A seasonal change occurred between metabolic groups as main Hg producers.•Methanogenic Archaea are the principal Hg methylators in the flood season.•Sulfate-reducing bacteria assume this role during the dry season.•In addition, periphytic algal primary productivity contributed to MeHg production.