Seasonal evolution of net and regenerated silica production around a natural Fe-fertilized area in the Southern Ocean estimated with Si isotopic approaches
A massive diatom bloom is observed each year in the surface waters of the naturally Fe-fertilized Kerguelen Plateau (Southern Ocean). We measured biogenic silica production and dissolution fluxes (ρSi and ρDiss, respectively) in the mixed layer in the vicinity of the Kerguelen Plateau during austral...
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Copernicus Publications
2014
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ftdoajarticles:oai:doaj.org/article:ea8d7b05019d4d66ab3dae87808b7253 2023-05-15T18:25:03+02:00 Seasonal evolution of net and regenerated silica production around a natural Fe-fertilized area in the Southern Ocean estimated with Si isotopic approaches I. Closset M. Lasbleiz K. Leblanc B. Quéguiner A.-J. Cavagna M. Elskens J. Navez D. Cardinal 2014-10-01T00:00:00Z https://doi.org/10.5194/bg-11-5827-2014 https://doaj.org/article/ea8d7b05019d4d66ab3dae87808b7253 EN eng Copernicus Publications http://www.biogeosciences.net/11/5827/2014/bg-11-5827-2014.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 1726-4170 1726-4189 doi:10.5194/bg-11-5827-2014 https://doaj.org/article/ea8d7b05019d4d66ab3dae87808b7253 Biogeosciences, Vol 11, Iss 20, Pp 5827-5846 (2014) Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 article 2014 ftdoajarticles https://doi.org/10.5194/bg-11-5827-2014 2022-12-31T02:26:37Z A massive diatom bloom is observed each year in the surface waters of the naturally Fe-fertilized Kerguelen Plateau (Southern Ocean). We measured biogenic silica production and dissolution fluxes (ρSi and ρDiss, respectively) in the mixed layer in the vicinity of the Kerguelen Plateau during austral spring 2011 (KEOPS-2 cruise). We compare results from a high-nutrient low-chlorophyll reference station and stations with different degrees of iron enrichment and bloom conditions. Above the plateau biogenic ρSi are among the highest reported so far in the Southern Ocean (up to 47.9 mmol m −2 d −1 ). Although significant (10.2 mmol m −2 d −1 on average), ρDiss were generally much lower than production rates. Uptake ratios (ρSi : ρC and ρSi : ρN) confirm that diatoms strongly dominate primary production in this area. At the bloom onset, decreasing dissolution-to-production ratios (D : P) indicate that the remineralization of silica could sustain most of the low silicon uptake and that the system progressively shifts toward a silica production regime which must be mainly supported by new source of silicic acid. Moreover, by comparing results from the two KEOPS expeditions (spring 2011 and summer 2005), we suggest that there is a seasonal evolution of the processes decoupling Si and N cycles in the area. Indeed, the consumption of H 4 SiO 4 standing stocks occurs only during the growing stage of the bloom when strong net silica production is observed, contributing to higher H 4 SiO 4 depletion relative to NO 3 − . Then, the decoupling of H 4 SiO 4 and NO 3 − is mainly controlled by the more efficient nitrogen recycling relative to Si. Gross Si : N uptake ratios were higher in the Fe-rich regions compared to the high-nutrient low-chlorophyll (HNLC) area, likely due to different diatom communities. This suggests that the diatom responses to natural Fe fertilization are more complex than previously thought, and that natural iron fertilization over long timescales does not necessarily decrease Si : N uptake ratios as ... Article in Journal/Newspaper Southern Ocean Directory of Open Access Journals: DOAJ Articles Austral Kerguelen Southern Ocean Biogeosciences 11 20 5827 5846 |
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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 I. Closset M. Lasbleiz K. Leblanc B. Quéguiner A.-J. Cavagna M. Elskens J. Navez D. Cardinal Seasonal evolution of net and regenerated silica production around a natural Fe-fertilized area in the Southern Ocean estimated with Si isotopic approaches |
topic_facet |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 |
description |
A massive diatom bloom is observed each year in the surface waters of the naturally Fe-fertilized Kerguelen Plateau (Southern Ocean). We measured biogenic silica production and dissolution fluxes (ρSi and ρDiss, respectively) in the mixed layer in the vicinity of the Kerguelen Plateau during austral spring 2011 (KEOPS-2 cruise). We compare results from a high-nutrient low-chlorophyll reference station and stations with different degrees of iron enrichment and bloom conditions. Above the plateau biogenic ρSi are among the highest reported so far in the Southern Ocean (up to 47.9 mmol m −2 d −1 ). Although significant (10.2 mmol m −2 d −1 on average), ρDiss were generally much lower than production rates. Uptake ratios (ρSi : ρC and ρSi : ρN) confirm that diatoms strongly dominate primary production in this area. At the bloom onset, decreasing dissolution-to-production ratios (D : P) indicate that the remineralization of silica could sustain most of the low silicon uptake and that the system progressively shifts toward a silica production regime which must be mainly supported by new source of silicic acid. Moreover, by comparing results from the two KEOPS expeditions (spring 2011 and summer 2005), we suggest that there is a seasonal evolution of the processes decoupling Si and N cycles in the area. Indeed, the consumption of H 4 SiO 4 standing stocks occurs only during the growing stage of the bloom when strong net silica production is observed, contributing to higher H 4 SiO 4 depletion relative to NO 3 − . Then, the decoupling of H 4 SiO 4 and NO 3 − is mainly controlled by the more efficient nitrogen recycling relative to Si. Gross Si : N uptake ratios were higher in the Fe-rich regions compared to the high-nutrient low-chlorophyll (HNLC) area, likely due to different diatom communities. This suggests that the diatom responses to natural Fe fertilization are more complex than previously thought, and that natural iron fertilization over long timescales does not necessarily decrease Si : N uptake ratios as ... |
format |
Article in Journal/Newspaper |
author |
I. Closset M. Lasbleiz K. Leblanc B. Quéguiner A.-J. Cavagna M. Elskens J. Navez D. Cardinal |
author_facet |
I. Closset M. Lasbleiz K. Leblanc B. Quéguiner A.-J. Cavagna M. Elskens J. Navez D. Cardinal |
author_sort |
I. Closset |
title |
Seasonal evolution of net and regenerated silica production around a natural Fe-fertilized area in the Southern Ocean estimated with Si isotopic approaches |
title_short |
Seasonal evolution of net and regenerated silica production around a natural Fe-fertilized area in the Southern Ocean estimated with Si isotopic approaches |
title_full |
Seasonal evolution of net and regenerated silica production around a natural Fe-fertilized area in the Southern Ocean estimated with Si isotopic approaches |
title_fullStr |
Seasonal evolution of net and regenerated silica production around a natural Fe-fertilized area in the Southern Ocean estimated with Si isotopic approaches |
title_full_unstemmed |
Seasonal evolution of net and regenerated silica production around a natural Fe-fertilized area in the Southern Ocean estimated with Si isotopic approaches |
title_sort |
seasonal evolution of net and regenerated silica production around a natural fe-fertilized area in the southern ocean estimated with si isotopic approaches |
publisher |
Copernicus Publications |
publishDate |
2014 |
url |
https://doi.org/10.5194/bg-11-5827-2014 https://doaj.org/article/ea8d7b05019d4d66ab3dae87808b7253 |
geographic |
Austral Kerguelen Southern Ocean |
geographic_facet |
Austral Kerguelen Southern Ocean |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_source |
Biogeosciences, Vol 11, Iss 20, Pp 5827-5846 (2014) |
op_relation |
http://www.biogeosciences.net/11/5827/2014/bg-11-5827-2014.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 1726-4170 1726-4189 doi:10.5194/bg-11-5827-2014 https://doaj.org/article/ea8d7b05019d4d66ab3dae87808b7253 |
op_doi |
https://doi.org/10.5194/bg-11-5827-2014 |
container_title |
Biogeosciences |
container_volume |
11 |
container_issue |
20 |
container_start_page |
5827 |
op_container_end_page |
5846 |
_version_ |
1766206215966162944 |