Methane distribution and oxidation around the Lena Delta in summer 2013
The Lena River is one of the largest Russian rivers draining into the Laptev Sea. The predicted increases in global temperatures are expected to cause the permafrost areas surrounding the Lena Delta to melt at increasing rates. This melting will result in high amounts of methane reaching the waters...
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ftcopernicus:oai:publications.copernicus.org:bg57065 2023-05-15T17:07:17+02:00 Methane distribution and oxidation around the Lena Delta in summer 2013 Bussmann, Ingeborg Hackbusch, Steffen Schaal, Patrick Wichels, Antje 2018-09-27 application/pdf https://doi.org/10.5194/bg-14-4985-2017 https://www.biogeosciences.net/14/4985/2017/ eng eng doi:10.5194/bg-14-4985-2017 https://www.biogeosciences.net/14/4985/2017/ eISSN: 1726-4189 Text 2018 ftcopernicus https://doi.org/10.5194/bg-14-4985-2017 2019-12-24T09:50:54Z The Lena River is one of the largest Russian rivers draining into the Laptev Sea. The predicted increases in global temperatures are expected to cause the permafrost areas surrounding the Lena Delta to melt at increasing rates. This melting will result in high amounts of methane reaching the waters of the Lena and the adjacent Laptev Sea. The only biological sink that can lower methane concentrations within this system is methane oxidation by methanotrophic bacteria. However, the polar estuary of the Lena River, due to its strong fluctuations in salinity and temperature, is a challenging environment for bacteria. We determined the activity and abundance of aerobic methanotrophic bacteria by a tracer method and by the quantitative polymerase chain reaction. We described the methanotrophic population with a molecular fingerprinting method (monooxygenase intergenic spacer analysis), as well as the methane distribution (via a headspace method) and other abiotic parameters, in the Lena Delta in September 2013. The median methane concentrations were 22 nmol L −1 for riverine water (salinity ( S ) < 5), 19 nmol L −1 for mixed water (5 < S < 20) and 28 nmol L −1 for polar water ( S > 20). The Lena River was not the source of methane in surface water, and the methane concentrations of the bottom water were mainly influenced by the methane concentration in surface sediments. However, the bacterial populations of the riverine and polar waters showed similar methane oxidation rates (0.419 and 0.400 nmol L −1 d −1 ), despite a higher relative abundance of methanotrophs and a higher estimated diversity in the riverine water than in the polar water. The methane turnover times ranged from 167 days in mixed water and 91 days in riverine water to only 36 days in polar water. The environmental parameters influencing the methane oxidation rate and the methanotrophic population also differed between the water masses. We postulate the presence of a riverine methanotrophic population that is limited by sub-optimal temperatures and substrate concentrations and a polar methanotrophic population that is well adapted to the cold and methane-poor polar environment but limited by a lack of nitrogen. The diffusive methane flux into the atmosphere ranged from 4 to 163 µmol m 2 d −1 (median 24). The diffusive methane flux accounted for a loss of 8 % of the total methane inventory of the investigated area, whereas the methanotrophic bacteria consumed only 1 % of this methane inventory. Our results underscore the importance of measuring the methane oxidation activities in polar estuaries, and they indicate a population-level differentiation between riverine and polar water methanotrophs. Text laptev Laptev Sea lena delta lena river permafrost Copernicus Publications: E-Journals Laptev Sea Biogeosciences 14 21 4985 5002 |
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Open Polar |
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Copernicus Publications: E-Journals |
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English |
description |
The Lena River is one of the largest Russian rivers draining into the Laptev Sea. The predicted increases in global temperatures are expected to cause the permafrost areas surrounding the Lena Delta to melt at increasing rates. This melting will result in high amounts of methane reaching the waters of the Lena and the adjacent Laptev Sea. The only biological sink that can lower methane concentrations within this system is methane oxidation by methanotrophic bacteria. However, the polar estuary of the Lena River, due to its strong fluctuations in salinity and temperature, is a challenging environment for bacteria. We determined the activity and abundance of aerobic methanotrophic bacteria by a tracer method and by the quantitative polymerase chain reaction. We described the methanotrophic population with a molecular fingerprinting method (monooxygenase intergenic spacer analysis), as well as the methane distribution (via a headspace method) and other abiotic parameters, in the Lena Delta in September 2013. The median methane concentrations were 22 nmol L −1 for riverine water (salinity ( S ) < 5), 19 nmol L −1 for mixed water (5 < S < 20) and 28 nmol L −1 for polar water ( S > 20). The Lena River was not the source of methane in surface water, and the methane concentrations of the bottom water were mainly influenced by the methane concentration in surface sediments. However, the bacterial populations of the riverine and polar waters showed similar methane oxidation rates (0.419 and 0.400 nmol L −1 d −1 ), despite a higher relative abundance of methanotrophs and a higher estimated diversity in the riverine water than in the polar water. The methane turnover times ranged from 167 days in mixed water and 91 days in riverine water to only 36 days in polar water. The environmental parameters influencing the methane oxidation rate and the methanotrophic population also differed between the water masses. We postulate the presence of a riverine methanotrophic population that is limited by sub-optimal temperatures and substrate concentrations and a polar methanotrophic population that is well adapted to the cold and methane-poor polar environment but limited by a lack of nitrogen. The diffusive methane flux into the atmosphere ranged from 4 to 163 µmol m 2 d −1 (median 24). The diffusive methane flux accounted for a loss of 8 % of the total methane inventory of the investigated area, whereas the methanotrophic bacteria consumed only 1 % of this methane inventory. Our results underscore the importance of measuring the methane oxidation activities in polar estuaries, and they indicate a population-level differentiation between riverine and polar water methanotrophs. |
format |
Text |
author |
Bussmann, Ingeborg Hackbusch, Steffen Schaal, Patrick Wichels, Antje |
spellingShingle |
Bussmann, Ingeborg Hackbusch, Steffen Schaal, Patrick Wichels, Antje Methane distribution and oxidation around the Lena Delta in summer 2013 |
author_facet |
Bussmann, Ingeborg Hackbusch, Steffen Schaal, Patrick Wichels, Antje |
author_sort |
Bussmann, Ingeborg |
title |
Methane distribution and oxidation around the Lena Delta in summer 2013 |
title_short |
Methane distribution and oxidation around the Lena Delta in summer 2013 |
title_full |
Methane distribution and oxidation around the Lena Delta in summer 2013 |
title_fullStr |
Methane distribution and oxidation around the Lena Delta in summer 2013 |
title_full_unstemmed |
Methane distribution and oxidation around the Lena Delta in summer 2013 |
title_sort |
methane distribution and oxidation around the lena delta in summer 2013 |
publishDate |
2018 |
url |
https://doi.org/10.5194/bg-14-4985-2017 https://www.biogeosciences.net/14/4985/2017/ |
geographic |
Laptev Sea |
geographic_facet |
Laptev Sea |
genre |
laptev Laptev Sea lena delta lena river permafrost |
genre_facet |
laptev Laptev Sea lena delta lena river permafrost |
op_source |
eISSN: 1726-4189 |
op_relation |
doi:10.5194/bg-14-4985-2017 https://www.biogeosciences.net/14/4985/2017/ |
op_doi |
https://doi.org/10.5194/bg-14-4985-2017 |
container_title |
Biogeosciences |
container_volume |
14 |
container_issue |
21 |
container_start_page |
4985 |
op_container_end_page |
5002 |
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1766062661388206080 |