The dominant role of sunlight in degrading winter dissolved organic matter from a thermokarst lake in a subarctic peatland
Dissolved organic matter (DOM) leaching from thawing permafrost may promote a positive feedback on the climate if it is efficiently mineralized into greenhouse gases. However, many uncertainties remain on the extent of this mineralization, which depends on DOM lability that is seemingly quite variab...
Published in: | Biogeosciences |
---|---|
Main Authors: | , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Copernicus Publications
2022
|
Subjects: | |
Online Access: | https://doi.org/10.5194/bg-19-3959-2022 https://doaj.org/article/43eb11fe074a412d8e8e2ab8a90ef114 |
id |
ftdoajarticles:oai:doaj.org/article:43eb11fe074a412d8e8e2ab8a90ef114 |
---|---|
record_format |
openpolar |
spelling |
ftdoajarticles:oai:doaj.org/article:43eb11fe074a412d8e8e2ab8a90ef114 2023-05-15T16:37:57+02:00 The dominant role of sunlight in degrading winter dissolved organic matter from a thermokarst lake in a subarctic peatland F. Mazoyer I. Laurion M. Rautio 2022-08-01T00:00:00Z https://doi.org/10.5194/bg-19-3959-2022 https://doaj.org/article/43eb11fe074a412d8e8e2ab8a90ef114 EN eng Copernicus Publications https://bg.copernicus.org/articles/19/3959/2022/bg-19-3959-2022.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 doi:10.5194/bg-19-3959-2022 1726-4170 1726-4189 https://doaj.org/article/43eb11fe074a412d8e8e2ab8a90ef114 Biogeosciences, Vol 19, Pp 3959-3977 (2022) Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 article 2022 ftdoajarticles https://doi.org/10.5194/bg-19-3959-2022 2022-12-30T23:43:05Z Dissolved organic matter (DOM) leaching from thawing permafrost may promote a positive feedback on the climate if it is efficiently mineralized into greenhouse gases. However, many uncertainties remain on the extent of this mineralization, which depends on DOM lability that is seemingly quite variable across landscapes. Thermokarst peatlands are organic-rich systems where some of the largest greenhouse gas (GHG) emission rates have been measured. At spring turnover, anoxic waters release the GHG accumulated in winter, and the DOM pool is exposed to sunlight. Here, we present an experiment where DOM photoreactivity and bioreactivity were investigated in water collected from a thermokarst lake in a subarctic peatland during late winter (after 6 months of darkness). We applied treatment with or without light exposure, and manipulated the bacterial abundance with the aim to quantify the unique and combined effects of light and bacteria on DOM reactivity at ice-off in spring. We demonstrate that sunlight was clearly driving the transformation of the DOM pool, part of which went through a complete mineralization into CO 2 . Up to 18 % of the initial dissolved organic carbon (DOC, a loss of 3.9 mgC L −1 ) was lost over 18 d of sunlight exposure in a treatment where bacterial abundance was initially reduced by 95 %. However, sunlight considerably stimulated bacterial growth when grazers were eliminated, leading to the recovery of the original bacterial abundance in about 8 d, which may have contributed to the DOC loss. Indeed, the highest DOC loss was observed for the treatment with the full bacterial community exposed to sunlight (5.0 mgC L −1 ), indicating an indirect effect of light through the bacterial consumption of photoproducts. Dark incubations led to very limited changes in DOC, regardless of the bacterial abundance and activity. The results also show that only half of the light-associated DOC losses were converted into CO 2 , and we suggest that the rest potentially turned into particles through ... Article in Journal/Newspaper Ice permafrost Subarctic Thermokarst Directory of Open Access Journals: DOAJ Articles Biogeosciences 19 17 3959 3977 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 |
spellingShingle |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 F. Mazoyer I. Laurion M. Rautio The dominant role of sunlight in degrading winter dissolved organic matter from a thermokarst lake in a subarctic peatland |
topic_facet |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 |
description |
Dissolved organic matter (DOM) leaching from thawing permafrost may promote a positive feedback on the climate if it is efficiently mineralized into greenhouse gases. However, many uncertainties remain on the extent of this mineralization, which depends on DOM lability that is seemingly quite variable across landscapes. Thermokarst peatlands are organic-rich systems where some of the largest greenhouse gas (GHG) emission rates have been measured. At spring turnover, anoxic waters release the GHG accumulated in winter, and the DOM pool is exposed to sunlight. Here, we present an experiment where DOM photoreactivity and bioreactivity were investigated in water collected from a thermokarst lake in a subarctic peatland during late winter (after 6 months of darkness). We applied treatment with or without light exposure, and manipulated the bacterial abundance with the aim to quantify the unique and combined effects of light and bacteria on DOM reactivity at ice-off in spring. We demonstrate that sunlight was clearly driving the transformation of the DOM pool, part of which went through a complete mineralization into CO 2 . Up to 18 % of the initial dissolved organic carbon (DOC, a loss of 3.9 mgC L −1 ) was lost over 18 d of sunlight exposure in a treatment where bacterial abundance was initially reduced by 95 %. However, sunlight considerably stimulated bacterial growth when grazers were eliminated, leading to the recovery of the original bacterial abundance in about 8 d, which may have contributed to the DOC loss. Indeed, the highest DOC loss was observed for the treatment with the full bacterial community exposed to sunlight (5.0 mgC L −1 ), indicating an indirect effect of light through the bacterial consumption of photoproducts. Dark incubations led to very limited changes in DOC, regardless of the bacterial abundance and activity. The results also show that only half of the light-associated DOC losses were converted into CO 2 , and we suggest that the rest potentially turned into particles through ... |
format |
Article in Journal/Newspaper |
author |
F. Mazoyer I. Laurion M. Rautio |
author_facet |
F. Mazoyer I. Laurion M. Rautio |
author_sort |
F. Mazoyer |
title |
The dominant role of sunlight in degrading winter dissolved organic matter from a thermokarst lake in a subarctic peatland |
title_short |
The dominant role of sunlight in degrading winter dissolved organic matter from a thermokarst lake in a subarctic peatland |
title_full |
The dominant role of sunlight in degrading winter dissolved organic matter from a thermokarst lake in a subarctic peatland |
title_fullStr |
The dominant role of sunlight in degrading winter dissolved organic matter from a thermokarst lake in a subarctic peatland |
title_full_unstemmed |
The dominant role of sunlight in degrading winter dissolved organic matter from a thermokarst lake in a subarctic peatland |
title_sort |
dominant role of sunlight in degrading winter dissolved organic matter from a thermokarst lake in a subarctic peatland |
publisher |
Copernicus Publications |
publishDate |
2022 |
url |
https://doi.org/10.5194/bg-19-3959-2022 https://doaj.org/article/43eb11fe074a412d8e8e2ab8a90ef114 |
genre |
Ice permafrost Subarctic Thermokarst |
genre_facet |
Ice permafrost Subarctic Thermokarst |
op_source |
Biogeosciences, Vol 19, Pp 3959-3977 (2022) |
op_relation |
https://bg.copernicus.org/articles/19/3959/2022/bg-19-3959-2022.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 doi:10.5194/bg-19-3959-2022 1726-4170 1726-4189 https://doaj.org/article/43eb11fe074a412d8e8e2ab8a90ef114 |
op_doi |
https://doi.org/10.5194/bg-19-3959-2022 |
container_title |
Biogeosciences |
container_volume |
19 |
container_issue |
17 |
container_start_page |
3959 |
op_container_end_page |
3977 |
_version_ |
1766028251587674112 |