Mercury methylation in Sphagnum moss mats and its association with sulfate-reducing bacteria in an acidic Adirondack forest lake wetland.
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.
Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, NJ 08901, USA. rqyu@eden.rutgers.edu
Ri-Qing
RQ
Yu
Isaac
I
Adatto
Mario R
MR
Montesdeoca
Charles T
CT
Driscoll
Mark E
ME
Hines
Tamar
T
Barkay
D000143:Acids; D004269:DNA, Bacterial / Q000235:genetics; D058645:Denaturing Gradient Gel Electrophoresis; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology; D008745:Methylation; D008767:Methylmercury Compounds / Q000378:metabolism*; D009518:New York; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D044003:Sphagnopsida / Q000382:microbiology*; D013431:Sulfates / Q000378:metabolism; D016999:Sulfur-Reducing Bacteria / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D014197:Trees; D053833:Wetlands
D000143:Acids; D004269:DNA, Bacterial; D008767:Methylmercury Compounds; D012336:RNA, Ribosomal, 16S; D013431:Sulfates