Evidence of Mercury Methylation and Demethylation by the Estuarine Microbial Communities Obtained in Stable Hg Isotope Studies

Neusa Figueiredo, Maria Luísa Serralheiro, João Canário, Aida Duarte, Holger Hintelmann and Cristina Carvalho
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Neusa Figueiredo: Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
Maria Luísa Serralheiro: BioISI—Biosystems & Integrative Sciences Institute, Faculty of Sciences, Universidade de Lisboa, Campo Grande C8, 1749-016 Lisboa, Portugal
João Canário: Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal
Aida Duarte: Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
Holger Hintelmann: Chemistry Department, Trent University, 1600 West Bank Drive, Peterborough, ON K9J 0G2, Canada
Cristina Carvalho: Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal

IJERPH, 2018, vol. 15, issue 10, 1-13

Abstract: Microbial activity is a critical factor controlling methylmercury formation in aquatic environments. Microbial communities were isolated from sediments of two highly mercury-polluted areas of the Tagus Estuary (Barreiro and Cala do Norte) and differentiated according to their dependence on oxygen into three groups: aerobic, anaerobic, and sulphate-reducing microbial communities. Their potential to methylate mercury and demethylate methylmercury was evaluated through incubation with isotope-enriched Hg species ( 199 HgCl and CH 3 201 HgCl). The results showed that the isolated microbial communities are actively involved in methylation and demethylation processes. The production of CH 3 199 Hg was positively correlated with sulphate-reducing microbial communities, methylating up to 0.07% of the added 199 Hg within 48 h of incubation. A high rate of CH 3 201 Hg degradation was observed and >20% of CH 3 201 Hg was transformed. Mercury removal of inorganic forms was also observed. The results prove the simultaneous occurrence of microbial methylation and demethylation processes and indicate that microorganisms are mainly responsible for methylmercury formation and accumulation in the polluted Tagus Estuary.

Keywords: bacteria; SRB; estuaries; methylmercury; mercury; methylation; demethylation; biogeochemistry; estuarine chemistry; mercury isotopes (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2018
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