Journal Article

Mercury methylation in <i>Sphagnum</i> moss mats and its association with sulfate-reducing bacteria in an acidic Adirondack forest lake wetland

Ri-Qing Yu, Isaac Adatto, Mario R. Montesdeoca, Charles T. Driscoll, Mark E. Hines and Tamar Barkay

in FEMS Microbiology Ecology

Volume 74, issue 3, pages 655-668
Published in print December 2010 |
Published online November 2010 | e-ISSN: 1574-6941 | DOI: http://dx.doi.org/10.1111/j.1574-6941.2010.00978.x

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Abstract

Processes leading to the bioaccumulation of methylmercury (MeHg) in northern wetlands are largely unknown. We have studied various ecological niches within a remote, acidic forested lake ecosystem in the southwestern Adirondacks, NY, to discover that mats comprised of Sphagnum moss were a hot spot for mercury (Hg) and MeHg accumulation (190.5 and 18.6 ng g−1 dw, respectively). Furthermore, significantly higher potential methylation rates were measured in Sphagnum mats as compared with other sites within Sunday Lake's ecosystem. Although MPN estimates showed a low biomass of sulfate-reducing bacteria (SRB), 2.8 × 104 cells mL−1 in mat samples, evidence consisting of (1) a twofold stimulation of potential methylation by the addition of sulfate, (2) a significant decrease in Hg methylation in the presence of the sulfate reduction inhibitor molybdate, and (3) presence of dsrAB-like genes in mat DNA extracts, suggested that SRB were involved in Hg methylation. Sequencing of dsrB genes indicated that novel SRB, incomplete oxidizers including Desulfobulbus spp. and Desulfovibrio spp., and syntrophs dominated the sulfate-reducing guild in the Sphagnum moss mat. Sphagnum, a bryophyte dominating boreal peatlands, and its associated microbial communities appear to play an important role in the production and accumulation of MeHg in high-latitude ecosystems.

Keywords: Hg methylation; Sphagnum moss mats; sulfate-reducing bacteria; acidic Adirondack lake wetland

Journal Article.  8702 words.  Illustrated.

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