Bottom-up methane dynamics along the degradation of permafrost: A case study on microbial communities of the methane cycle in a collapsing sub-Arctic palsa mire Susanne Liebner, Lars Ganzert, Andrea Kiss, Erin C. Seybold, Dirk Wagner, and Mette M. Svenning PERGAMON meeting, Gent 5-7 November, 2012

2 Netherlands Institute of Ecology MPI for Terrestrial Microbiology, Germany University of Trømso, Norway ETH Zurich, Switzerland University of Warwick Free University of Amsterdam University of Vienna Associated Partners: ARC Seibersdorf MEthanotrophic diversity and gene expression as a COntrolling factor of global MEthane CONsumption

Study Site - Palsa Mires Composed of a core of frozen peat Form and erode naturally over time Distribution of palsa peatlands in Norway Successional Gradient Collapsed palsa (CP) Thermokarst pond (TP)Degrading palsa (DP)

Acidic peatland (pH ) Susceptible to climate change, rapidly collapsing Extremely limited in nitrogen (pore water NH 4 and NO 3 around detection limit, C:N ratios between Carbon content 44-54% Study Site - Characteristics Successional Gradient Collapsed palsa (CP) Thermokarst pond (TP)Degrading palsa (DP)

Palsa mires – Succession CH4 emissions and concentrations in the soil: < 200 mg/m2/d ~125 (±200) µM up to >600 mg/m2/d ~230 µM (±234) µM Below detection

Objectives Combine activity, abundance and community structure of methanogenic archaea and methanotrophic bacteria with methane emission/pore water measurements along permafrost degradation and mire succession

Potential Activity of Methanogens and Methanotrophs

Abundance of Methanogens and Methanotrophs

Community Structure of Methanogens TP 0-10 cm cm cm cm CP

Community Structure of Methanotrophs pmoA pyrosequencing

Community Structure of Methanotrophs pmoA clone libraries ‘species‘ distribution and abundance

Potential ‘very-potent’ methanotroph Ecosystem services of Methanotrophs beyond Methane Oxidation ?! sMMO CH4, aromatic comp, xenobiotics …??? pMMO CH4 Substrate Nitrogenase N2 pMMO – membrane bound sMMO - vesicles

Ecosystem services of Methanotrophs beyond Methane Oxidation ?!! neighbor joining tree of partial MmoX sequences Methylomonas related Beijerinckiaceae Methylocystis -transcripts of mmoX and MOB related nifH!! (Liebner & Svenning AEM, in press)

Summary Methane emissions, concentrations and community data coincide Methanogenesis and community of MA establish rapidly along with thermokarst formation Methanotrophs more abundant in ‘older‘ mire sites; potential to consume all methane (if accessible) Zones of max. methane production and consumption decoupled in thermokarst (Eriophorum) site but overlapping in older (Carex) site  Typical development for permafrost degradation; young vs.old mire sites; change in vegetation?

KEY FUNCTIONS AND MICROORGANISMS DRIVING ORGANIC CARBON TRANSFORMATION IN HIGH-ARCTIC PEAT SOILS Alexander Tveit Tim Urich, Rainer Schwacke, Peter Frenzel, Mette Svenning

Research questions Who are the key microorganisms in the Arctic peat soils? Which functions are available for degrading the soil organic carbon? Is the functional potential for SOC degradation in Arctic peat soils unique? What is the effect of temperature on the rate of anaerobic decomposition?

Research questions Who are the key microorganisms in the Arctic peat soils? Which functions are available for degrading the soil organic carbon? Is the functional potential for SOC degradation in Arctic peat soils unique? Tveit et al. ISME J (2012)

Research questions Who are the key microorganisms in the Arctic peat soils? Which functions are available for degrading the soil organic carbon? Is the functional potential for SOC degradation in Arctic peat soils unique? What is the effect of temperature on the rate of anaerobic decomposition? Anaysed from T gradient incubations: Accumulation of methane and fermentation products, Illumina sequencing of Metatranscriptomes Preliminary data: Downstream degradation represented a rate limiting step for terminal mineralization at low temperature Unlike the microbiota from temperate soils, the arctic peat communities were well adapted to low temperatures responding even to a very modest temperature increase.

Thank you!!