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Rapid Permafrost Thaw Removes Nitrogen Limitation and Rises the Potential for N2O Emissions. NITROGEN 2022. [DOI: 10.3390/nitrogen3040040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ice–rich Pleistocene permafrost deposits (Yedoma) store large amounts of nitrogen (N) and are susceptible to rapid thaw. In this study, we assess whether eroding Yedoma deposits are potential sources of N and gaseous carbon (C) losses. Therefore, we determined aerobic net ammonification and nitrification, as well as anaerobic production of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) in laboratory incubations. Samples were collected from non-vegetated and revegetated slump floor (SF) and thaw mound (TM) soils of a retrogressive thaw slump in the Lena River Delta of Eastern Siberia. We found high nitrate concentrations (up to 110 µg N (g DW)−1) within the growing season, a faster transformation of organic N to nitrate, and high N2O production (up to 217 ng N2O-N (g DW)−1 day−1) in revegetated thaw mounds. The slump floor was low in nitrate and did not produce N2O under anaerobic conditions, but produced the most CO2 (up to 7 µg CO2-C (g DW)−1 day−1) and CH4 (up to 65 ng CH4-C (g DW)−1 day−1). Nitrate additions showed that denitrification was substrate limited in the slump floor. Nitrate limitation was rather caused by field conditions (moisture, pH) than by microbial functional limitation since nitrification rates were positive under laboratory conditions. Our results emphasize the relevance of considering landscape processes, geomorphology, and soil origin in order to identify hotspots of high N availability, as well as C and N losses. High N availability is likely to have an impact on carbon cycling, but to what extent needs further investigation.
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Microbiogeochemical Traits to Identify Nitrogen Hotspots in Permafrost Regions. NITROGEN 2022. [DOI: 10.3390/nitrogen3030031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Permafrost-affected tundra soils are large carbon (C) and nitrogen (N) reservoirs. However, N is largely bound in soil organic matter (SOM), and ecosystems generally have low N availability. Therefore, microbial induced N-cycling processes and N losses were considered negligible. Recent studies show that microbial N processing rates, inorganic N availability, and lateral N losses from thawing permafrost increase when vegetation cover is disturbed, resulting in reduced N uptake or increased N input from thawing permafrost. In this review, we describe currently known N hotspots, particularly bare patches in permafrost peatland or permafrost soils affected by thermokarst, and their microbiogeochemical characteristics, and present evidence for previously unrecorded N hotspots in the tundra. We summarize the current understanding of microbial N cycling processes that promote the release of the potent greenhouse gas (GHG) nitrous oxide (N2O) and the translocation of inorganic N from terrestrial into aquatic ecosystems. We suggest that certain soil characteristics and microbial traits can be used as indicators of N availability and N losses. Identifying N hotspots in permafrost soils is key to assessing the potential for N release from permafrost-affected soils under global warming, as well as the impact of increased N availability on emissions of carbon-containing GHGs.
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Thomas DN, Arévalo-Martínez DL, Crocket KC, Große F, Grosse J, Schulz K, Sühring R, Tessin A. A changing Arctic Ocean. AMBIO 2022; 51:293-297. [PMID: 34843100 PMCID: PMC8692628 DOI: 10.1007/s13280-021-01677-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Affiliation(s)
- David N. Thomas
- University of Helsinki, Viikinkaari 1, P.O. Box 65, 00014 Helsinki, Finland
| | | | | | - Fabian Große
- Department of Microbiology, Federal Institute of Hydrology, Am Mainzer Tor 1, 56068 Koblenz, Germany
| | | | - Kirstin Schulz
- 201 E. 24th Street, Stop C0200, Austin, TX 78712-1229 USA
| | - Roxana Sühring
- Department of Chemistry and Biology, Ryerson University, Toronto, ON M5B 2K3 Canada
| | - Allyson Tessin
- Department of Geology, Kent State University, 800 E Summit St, Kent, OH 44240 USA
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Tuerena RE, Mahaffey C, Henley SF, de la Vega C, Norman L, Brand T, Sanders T, Debyser M, Dähnke K, Braun J, März C. Nutrient pathways and their susceptibility to past and future change in the Eurasian Arctic Ocean. AMBIO 2022; 51:355-369. [PMID: 34914030 PMCID: PMC8692559 DOI: 10.1007/s13280-021-01673-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 09/20/2021] [Accepted: 11/12/2021] [Indexed: 05/25/2023]
Abstract
Climate change is altering nutrient cycling within the Arctic Ocean, having knock-on effects to Arctic ecosystems. Primary production in the Arctic is principally nitrogen-limited, particularly in the western Pacific-dominated regions where denitrification exacerbates nitrogen loss. The nutrient status of the eastern Eurasian Arctic remains under debate. In the Barents Sea, primary production has increased by 88% since 1998. To support this rapid increase in productivity, either the standing stock of nutrients has been depleted, or the external nutrient supply has increased. Atlantic water inflow, enhanced mixing, benthic nitrogen cycling, and land-ocean interaction have the potential to alter the nutrient supply through addition, dilution or removal. Here we use new datasets from the Changing Arctic Ocean program alongside historical datasets to assess how nitrate and phosphate concentrations may be changing in response to these processes. We highlight how nutrient dynamics may continue to change, why this is important for regional and international policy-making and suggest relevant research priorities for the future.
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Affiliation(s)
| | - Claire Mahaffey
- Department of Earth, Ocean and Ecological Sciences, School of Environmental Sciences, University of Liverpool, 4 Brownlow Street, Liverpool, L69 3GP Merseyside UK
| | - Sian F. Henley
- School of GeoSciences, University of Edinburgh, James Hutton Road, Edinburgh, EH9 3FE UK
| | - Camille de la Vega
- Department of Earth, Ocean and Ecological Sciences, School of Environmental Sciences, University of Liverpool, 4 Brownlow Street, Liverpool, L69 3GP Merseyside UK
| | - Louisa Norman
- Department of Earth, Ocean and Ecological Sciences, School of Environmental Sciences, University of Liverpool, 4 Brownlow Street, Liverpool, L69 3GP Merseyside UK
| | - Tim Brand
- Scottish Association for Marine Science, Oban, PA37 1QA UK
| | - Tina Sanders
- Institute for Carbon Cycles, Helmholtz-Zentrum Hereon, Max-Planck-Str. 1, 21502 Geesthacht, Germany
| | - Margot Debyser
- School of GeoSciences, University of Edinburgh, James Hutton Road, Edinburgh, EH9 3FE UK
| | - Kirstin Dähnke
- Institute for Carbon Cycles, Helmholtz-Zentrum Hereon, Max-Planck-Str. 1, 21502 Geesthacht, Germany
| | - Judith Braun
- Scottish Association for Marine Science, Oban, PA37 1QA UK
| | - Christian März
- School of Earth & Environment, University of Leeds, Leeds, LS2 9JT UK
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