Evidence for anaerobic oxidation of methane in sediments of a freshwater system (Lago di Cadagno).
Anaerobic oxidation of methane (AOM) has been investigated in sediments of a high alpine sulfate-rich lake. Hot spots of AOM could be identified based on geochemical and isotopic evidence. Very high fractionation of methane (α=1.031) during oxidation was observed in the uppermost sediment layers, where methane is oxidized most likely with sulfate-containing bottom waters. However, we could not exclude that other electron acceptors such as iron, or manganese might also be involved. Light carbon isotope values (δ¹³C = -10‰ vs. Vienna Pee Dee Belemnite [VPDB]) of sedimentary carbonates at 16-20 cm sediment depth are indicative of a zone where methane was oxidized and the resulting bicarbonate ions were used for carbonate precipitation. 16S rRNA gene analysis revealed the presence of sequences belonging to the marine benthic groups B, C, and D and to the recently described clade of AOM-associated archaea (AAA). Catalyzed reporter deposition-FISH analysis revealed a high abundance of Deltaproteobacteria, especially of free-living sulfate-reducing bacteria of the Desulfosarcina/Desulfococcus branch of Deltaproteobacteria in the AOM zone. Here, loose aggregations of AAA cells were found, suggesting that AAA might be responsible for oxidation of methane in Lake Cadagno sediments.
Department of Surface Waters-Research and Management, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Kastanienbaum, Switzerland. carsten.schubert@eawag.ch
Carsten J
CJ
Schubert
Francisco
F
Vazquez
Tina
T
Lösekann-Behrens
Katrin
K
Knittel
Mauro
M
Tonolla
Antje
A
Boetius
D000693:Anaerobiosis; D001105:Archaea / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D044822:Biodiversity; D002247:Carbon Isotopes / Q000032:analysis; D015169:Colony Count, Microbial; D019641:DNA, Archaeal / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D020564:Deltaproteobacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D005618:Fresh Water / Q000382:microbiology*; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology*; D008697:Methane / Q000378:metabolism*; D010084:Oxidation-Reduction; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013431:Sulfates / Q000378:metabolism; D013557:Switzerland; D014871:Water Microbiology
D002247:Carbon Isotopes; D019641:DNA, Archaeal; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D013431:Sulfates; D008697:Methane