Microbial iron(III) reduction during palsa collapse promotes greenhouse gas emissions before complete permafrost thaw

Abstract Reactive iron (Fe) minerals can preserve organic carbon (OC) in soils overlying intact permafrost. With permafrost thaw, reductive dissolution of iron minerals releases Fe and OC into the porewater, potentially increasing the bioavailability of OC for microbial decomposition. However, the stability of this so-called rusty carbon sink, the microbial community driving mineral dissolution, the identity of the iron-associated carbon and the resulting impact on greenhouse gas emissions are unknown. We examined palsa hillslopes, gradients from intact permafrost-supported palsa to semi-wet partially-thawed bog in a permafrost peatland in Abisko (Sweden). Using high-resolution mass spectrometry, we found that Fe-bound OC in intact palsa is comprised of loosely bound more aliphatic and strongly-bound more aromatic species. Iron mineral dissolution by both fermentative and dissimilatory Fe(III) reduction releases Fe-bound OC along the palsa hillslopes, before complete permafrost thaw. The increasing bioavailability of dissolved OC (DOC) leads to its further decomposition, demonstrated by an increasing nominal oxidation state of carbon (NOSC) and a peak in bioavailable acetate (61.7±42.6 mg C/L) at the collapsing palsa front. The aqueous Fe2+ released is partially re-oxidized by Fe(II)-oxidizing bacteria but cannot prevent the overall loss of the rusty carbon sink with palsa collapse. The increasing relative abundance and activity of Fe(III)-reducers is accompanied by an increasing abundance of methanogens and a peak in methane (CH4) emissions at the collapsing front. Our data suggest that the loss of the rusty carbon sink directly contributes to carbon dioxide (CO2) production by Fe(III) reduction coupled to OC oxidation and indirectly to CH4 emission by promoting methanogenesis even before complete permafrost thaw.

Download Full-text

Microbial iron(III) reduction during palsa collapse promotes greenhouse gas emissions before complete permafrost thaw

10.31223/x5v908 ◽

2021 ◽

Author(s):

Monique Patzner ◽

Merritt Logan ◽

Amy McKenna ◽

Robert Young ◽

Zhe Zhou ◽

...

Keyword(s):

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

High Resolution Mass Spectrometry ◽

Carbon Sink ◽

Mineral Dissolution ◽

Co2 Production ◽

Gas Emissions ◽

Microbial Decomposition ◽

Iron Mineral ◽

Permafrost Thaw

Reactive iron (Fe) minerals can preserve organic carbon (OC) in soils overlying intact permafrost. With permafrost thaw, reductive dissolution of iron minerals releases Fe and OC into the porewater, potentially increasing the bioavailability of OC for microbial decomposition. However, the stability of this so-called rusty carbon sink, the microbial community driving mineral dissolution, the identity of the iron-associated carbon and the resulting impact on greenhouse gas emissions are unknown. We examined palsa hillslopes, gradients from intact permafrost-supported palsa to semi-wet partially-thawed bog in a permafrost peatland in Abisko (Sweden). Using high-resolution mass spectrometry, we found that Fe-bound OC in intact palsa is comprised of loosely bound more aliphatic and strongly-bound more aromatic species. Iron mineral dissolution by both fermentative and dissimilatory Fe(III) reduction releases Fe-bound OC along the palsa hillslopes, before complete permafrost thaw. The increasing bioavailability of dissolved OC (DOC) leads to its further decomposition, demonstrated by an increasing nominal oxidation state of carbon (NOSC) and a peak in bioavailable acetate (61.7±42.6 mg C/L) at the collapsing palsa front. The aqueous Fe2+ released is partially re-oxidized by Fe(II)-oxidizing bacteria but cannot prevent the overall loss of the rusty carbon sink with palsa collapse. The increasing relative abundance and activity of Fe(III)-reducers is accompanied by an increasing abundance of methanogens and a peak in methane (CH4) emissions at the collapsing front. Our data suggest that the loss of the rusty carbon sink directly contributes to carbon dioxide (CO2) production by Fe(III) reduction coupled to OC oxidation and indirectly to CH4 emission by promoting methanogenesis even before complete permafrost thaw.

Download Full-text

Hotspots of greenhouse gas emissions – reducing the carbon sink potential of forest soils

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1307/6/8/082012 ◽

2009 ◽

Vol 6 (8) ◽

pp. 082012

Author(s):

Jesper Riis Christiansen ◽

P Gundersen ◽

L Vesterdal

Keyword(s):

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

Forest Soils ◽

Carbon Sink ◽

Gas Emissions

Download Full-text

Country-level land carbon sink and its causing components by the middle of the twenty-first century

Ecological Processes ◽

10.1186/s13717-021-00328-y ◽

2021 ◽

Vol 10 (1) ◽

Author(s):

Lifen Jiang ◽

Junyi Liang ◽

Xingjie Lu ◽

Enqing Hou ◽

Forrest M. Hoffman ◽

...

Keyword(s):

Climate Change ◽

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

Net Primary Production ◽

Carbon Sink ◽

Coupled Model ◽

Natural Ecosystems ◽

Gas Emissions ◽

Country Level ◽

C Storage

Abstract Background Countries have long been making efforts by reducing greenhouse-gas emissions to mitigate climate change. In the agreements of the United Nations Framework Convention on Climate Change, involved countries have committed to reduction targets. However, carbon (C) sink and its involving processes by natural ecosystems remain difficult to quantify. Methods Using a transient traceability framework, we estimated country-level land C sink and its causing components by 2050 simulated by 12 Earth System Models involved in the Coupled Model Intercomparison Project Phase 5 (CMIP5) under RCP8.5. Results The top 20 countries with highest C sink have the potential to sequester 62 Pg C in total, among which, Russia, Canada, USA, China, and Brazil sequester the most. This C sink consists of four components: production-driven change, turnover-driven change, change in instantaneous C storage potential, and interaction between production-driven change and turnover-driven change. The four components account for 49.5%, 28.1%, 14.5%, and 7.9% of the land C sink, respectively. Conclusion The model-based estimates highlight that land C sink potentially offsets a substantial proportion of greenhouse-gas emissions, especially for countries where net primary production (NPP) likely increases substantially and inherent residence time elongates.

Download Full-text

Iron mineral dissolution releases iron and associated organic carbon during permafrost thaw

Nature Communications ◽

10.1038/s41467-020-20102-6 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Monique S. Patzner ◽

Carsten W. Mueller ◽

Miroslava Malusova ◽

Moritz Baur ◽

Verena Nikeleit ◽

...

Keyword(s):

Organic Carbon ◽

Carbon Sink ◽

Mineral Dissolution ◽

Dynamic Interactions ◽

Terminal Electron Acceptor ◽

Iron Mineral ◽

Permafrost Thaw ◽

Reducing Conditions ◽

Carbon Release ◽

Reducing Bacteria

AbstractIt has been shown that reactive soil minerals, specifically iron(III) (oxyhydr)oxides, can trap organic carbon in soils overlying intact permafrost, and may limit carbon mobilization and degradation as it is observed in other environments. However, the use of iron(III)-bearing minerals as terminal electron acceptors in permafrost environments, and thus their stability and capacity to prevent carbon mobilization during permafrost thaw, is poorly understood. We have followed the dynamic interactions between iron and carbon using a space-for-time approach across a thaw gradient in Abisko (Sweden), where wetlands are expanding rapidly due to permafrost thaw. We show through bulk (selective extractions, EXAFS) and nanoscale analysis (correlative SEM and nanoSIMS) that organic carbon is bound to reactive Fe primarily in the transition between organic and mineral horizons in palsa underlain by intact permafrost (41.8 ± 10.8 mg carbon per g soil, 9.9 to 14.8% of total soil organic carbon). During permafrost thaw, water-logging and O2 limitation lead to reducing conditions and an increase in abundance of Fe(III)-reducing bacteria which favor mineral dissolution and drive mobilization of both iron and carbon along the thaw gradient. By providing a terminal electron acceptor, this rusty carbon sink is effectively destroyed along the thaw gradient and cannot prevent carbon release with thaw.

Download Full-text