In marine sediments, methane (CH4) is formed when organic matter is degraded via methanogenesis. A large fraction of the formed CH4 is typically removed via microbially mediated anaerobic oxidation of methane (AOM). During AOM, oxidation of CH4 can be coupled to reduction of, for example, sulfate, nitrate and iron and manganese (Mn) oxides. Increased eutrophication in coastal environments can lead to a higher production of CH4 and a shallowing of the sulfate-methane transition zone (SMTZ). This may result in an increased importance of metal oxides in AOM. To date, it is not known what microbes perform Mn-AOM in marine sediments and which types of Mn oxides are being used. In this study, we combine field data with batch incubations to explore novel pathways of AOM coupled to reduction of Mn oxides in sediments of a seasonally euxinic coastal marine basin (Lake Grevelingen, The Netherlands). Results of sediment and pore water analyses reveal that Mn oxides are buried below the SMTZ in layers that remain free of sulfide. Batch incubations in which sediment is supplied with isotopically labelled 13CH4 and Mn oxides show production of 13CO2 and the reduction of different forms of Mn oxides, including birnessite and pyrolusite. Analysis of the 16S rRNA genes reveal an increase of ANME-2a/b and ANME-3 when Mn oxides are reduced. Our results show that burial of Mn oxides in CH4-rich sediments of a seasonally euxinic coastal marine basin may lead to Mn-AOM, performed by anaerobic archaeal methanotrophs.
Primary Presenter: Robin Klomp, Radboud University (robin.klomp@ru.nl)
Authors:
Robin Klomp, Radboud University (robin.klomp@ru.nl)
Anna Wallenius, Radboud University (a.wallenius@science.ru.nl)
Wytze Lenstra, Utrecht University (W.K.Lenstra@uu.nl)
Niels van Helmond, Utrecht University (n.vanhelmond@uu.nl)
Olga Żygadłowska, Utrecht University (o.m.zygadlowska@uu.nl)
Rens Accou, Utrecht University (rens.accou@skynet.be)
Mike Jetten, Radboud University (mike.jetten@ru.nl)
Caroline Slomp, Radboud University (caroline.slomp@ru.nl)
MANGANESE-DRIVEN ANAEROBIC OXIDATION OF METHANE IN COASTAL MARINE SEDIMENTS
Category
Scientific Sessions > SS020 New Insights on The Methane and Nitrous Oxide Cycles from Freshwater and Marine Ecosystems Under Changing Climate
Description
Time: 11:00 AM
Date: 5/6/2023
Room: Auditorium Mallorca