Nitrate assimilation and regeneration in the Barents Sea: insights from nitrate isotopes
While the entire Arctic Ocean is warming rapidly, the Barents Sea in particular is experiencing significant warming and sea ice retreat. An increase in ocean heat transport from the Atlantic is causing the Barents Sea to be transformed from a cold, salinity-stratified system into a warmer, less-stra...
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Copernicus Publications
2021
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Online Access: | https://doi.org/10.5194/bg-18-637-2021 https://doaj.org/article/ebf1219402fe4c0e8fc33d295a97c6df |
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ftdoajarticles:oai:doaj.org/article:ebf1219402fe4c0e8fc33d295a97c6df 2023-05-15T14:29:12+02:00 Nitrate assimilation and regeneration in the Barents Sea: insights from nitrate isotopes R. E. Tuerena J. Hopkins R. S. Ganeshram L. Norman C. de la Vega R. Jeffreys C. Mahaffey 2021-01-01T00:00:00Z https://doi.org/10.5194/bg-18-637-2021 https://doaj.org/article/ebf1219402fe4c0e8fc33d295a97c6df EN eng Copernicus Publications https://bg.copernicus.org/articles/18/637/2021/bg-18-637-2021.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 doi:10.5194/bg-18-637-2021 1726-4170 1726-4189 https://doaj.org/article/ebf1219402fe4c0e8fc33d295a97c6df Biogeosciences, Vol 18, Pp 637-653 (2021) Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 article 2021 ftdoajarticles https://doi.org/10.5194/bg-18-637-2021 2022-12-31T05:39:30Z While the entire Arctic Ocean is warming rapidly, the Barents Sea in particular is experiencing significant warming and sea ice retreat. An increase in ocean heat transport from the Atlantic is causing the Barents Sea to be transformed from a cold, salinity-stratified system into a warmer, less-stratified Atlantic-dominated climate regime. Productivity in the Barents Sea shelf is fuelled by waters of Atlantic origin (AW) which are ultimately exported to the Arctic Basin. The consequences of this current regime shift on the nutrient characteristics of the Barents Sea are poorly defined. Here we use the stable isotopic ratios of nitrate ( δ 15 N- NO 3 , δ 18 O- NO 3 ) to determine the uptake and modification of AW nutrients in the Barents Sea. In summer months, phytoplankton consume nitrate, surface waters become nitrate depleted, and particulate nitrogen ( δ 15 N-PN) reflects the AW nitrate source. The ammonification of organic matter in shallow sediments resupplies N to the water column and replenishes the nitrate inventory for the following season. Low δ 18 O- NO 3 in the northern Barents Sea reveals that the nitrate in lower-temperature Arctic waters is > 80 % regenerated through seasonal nitrification. During on-shelf nutrient uptake and regeneration, there is no significant change to δ 15 N- NO 3 or N * , suggesting that benthic denitrification does not impart an isotopic imprint on pelagic nitrate. Our results demonstrate that the Barents Sea is distinct from other Arctic shelves where benthic denitrification enriches δ 15 N- NO 3 and decreases N * . As nutrients are efficiently recycled in the Barents Sea and there is no significant loss of N through benthic denitrification, changes to Barents Sea productivity are unlikely to alter N availability on shelf or the magnitude of N advected to the central Arctic Basin. However, we suggest that the AW nutrient source ultimately determines Barents Sea productivity and that changes to AW delivery have the potential to alter Barents Sea primary production and ... Article in Journal/Newspaper Arctic Basin Arctic Arctic Ocean Barents Sea Phytoplankton Sea ice Directory of Open Access Journals: DOAJ Articles Arctic Arctic Ocean Barents Sea Biogeosciences 18 2 637 653 |
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Open Polar |
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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 R. E. Tuerena J. Hopkins R. S. Ganeshram L. Norman C. de la Vega R. Jeffreys C. Mahaffey Nitrate assimilation and regeneration in the Barents Sea: insights from nitrate isotopes |
topic_facet |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 |
description |
While the entire Arctic Ocean is warming rapidly, the Barents Sea in particular is experiencing significant warming and sea ice retreat. An increase in ocean heat transport from the Atlantic is causing the Barents Sea to be transformed from a cold, salinity-stratified system into a warmer, less-stratified Atlantic-dominated climate regime. Productivity in the Barents Sea shelf is fuelled by waters of Atlantic origin (AW) which are ultimately exported to the Arctic Basin. The consequences of this current regime shift on the nutrient characteristics of the Barents Sea are poorly defined. Here we use the stable isotopic ratios of nitrate ( δ 15 N- NO 3 , δ 18 O- NO 3 ) to determine the uptake and modification of AW nutrients in the Barents Sea. In summer months, phytoplankton consume nitrate, surface waters become nitrate depleted, and particulate nitrogen ( δ 15 N-PN) reflects the AW nitrate source. The ammonification of organic matter in shallow sediments resupplies N to the water column and replenishes the nitrate inventory for the following season. Low δ 18 O- NO 3 in the northern Barents Sea reveals that the nitrate in lower-temperature Arctic waters is > 80 % regenerated through seasonal nitrification. During on-shelf nutrient uptake and regeneration, there is no significant change to δ 15 N- NO 3 or N * , suggesting that benthic denitrification does not impart an isotopic imprint on pelagic nitrate. Our results demonstrate that the Barents Sea is distinct from other Arctic shelves where benthic denitrification enriches δ 15 N- NO 3 and decreases N * . As nutrients are efficiently recycled in the Barents Sea and there is no significant loss of N through benthic denitrification, changes to Barents Sea productivity are unlikely to alter N availability on shelf or the magnitude of N advected to the central Arctic Basin. However, we suggest that the AW nutrient source ultimately determines Barents Sea productivity and that changes to AW delivery have the potential to alter Barents Sea primary production and ... |
format |
Article in Journal/Newspaper |
author |
R. E. Tuerena J. Hopkins R. S. Ganeshram L. Norman C. de la Vega R. Jeffreys C. Mahaffey |
author_facet |
R. E. Tuerena J. Hopkins R. S. Ganeshram L. Norman C. de la Vega R. Jeffreys C. Mahaffey |
author_sort |
R. E. Tuerena |
title |
Nitrate assimilation and regeneration in the Barents Sea: insights from nitrate isotopes |
title_short |
Nitrate assimilation and regeneration in the Barents Sea: insights from nitrate isotopes |
title_full |
Nitrate assimilation and regeneration in the Barents Sea: insights from nitrate isotopes |
title_fullStr |
Nitrate assimilation and regeneration in the Barents Sea: insights from nitrate isotopes |
title_full_unstemmed |
Nitrate assimilation and regeneration in the Barents Sea: insights from nitrate isotopes |
title_sort |
nitrate assimilation and regeneration in the barents sea: insights from nitrate isotopes |
publisher |
Copernicus Publications |
publishDate |
2021 |
url |
https://doi.org/10.5194/bg-18-637-2021 https://doaj.org/article/ebf1219402fe4c0e8fc33d295a97c6df |
geographic |
Arctic Arctic Ocean Barents Sea |
geographic_facet |
Arctic Arctic Ocean Barents Sea |
genre |
Arctic Basin Arctic Arctic Ocean Barents Sea Phytoplankton Sea ice |
genre_facet |
Arctic Basin Arctic Arctic Ocean Barents Sea Phytoplankton Sea ice |
op_source |
Biogeosciences, Vol 18, Pp 637-653 (2021) |
op_relation |
https://bg.copernicus.org/articles/18/637/2021/bg-18-637-2021.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 doi:10.5194/bg-18-637-2021 1726-4170 1726-4189 https://doaj.org/article/ebf1219402fe4c0e8fc33d295a97c6df |
op_doi |
https://doi.org/10.5194/bg-18-637-2021 |
container_title |
Biogeosciences |
container_volume |
18 |
container_issue |
2 |
container_start_page |
637 |
op_container_end_page |
653 |
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1766303268448763904 |