Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean
Natural iron fertilization of high-nutrient low-chlorophyll (HNLC) waters induces annually occurring spring phytoplankton blooms off the Kerguelen Islands (Southern Ocean). To examine the origin and fate of particulate and dissolved organic matter (POM and DOM), D- and L-amino acids (AA) were quanti...
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ftdoajarticles:oai:doaj.org/article:6782daa95e6e4ccb8b208fcb51cd6e77 2023-05-15T17:02:09+02:00 Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean L. Tremblay J. Caparros K. Leblanc I. Obernosterer 2015-01-01T00:00:00Z https://doi.org/10.5194/bg-12-607-2015 https://doaj.org/article/6782daa95e6e4ccb8b208fcb51cd6e77 EN eng Copernicus Publications http://www.biogeosciences.net/12/607/2015/bg-12-607-2015.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 1726-4170 1726-4189 doi:10.5194/bg-12-607-2015 https://doaj.org/article/6782daa95e6e4ccb8b208fcb51cd6e77 Biogeosciences, Vol 12, Iss 2, Pp 607-621 (2015) Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 article 2015 ftdoajarticles https://doi.org/10.5194/bg-12-607-2015 2022-12-31T01:37:09Z Natural iron fertilization of high-nutrient low-chlorophyll (HNLC) waters induces annually occurring spring phytoplankton blooms off the Kerguelen Islands (Southern Ocean). To examine the origin and fate of particulate and dissolved organic matter (POM and DOM), D- and L-amino acids (AA) were quantified at bloom and HNLC stations. Total hydrolyzable AA accounted for 21–25% of surface particulate organic carbon (%POC AA ) at the bloom sites, but for 10% at the HNLC site. A marked decrease in %POC AA with depth was observed at the most productive stations leading to values between 3 and 5% below 300 m depth. AA contributed to only 0.9–4.4% of dissolved organic carbon (%DOC AA ) at all stations. The only consistent vertical trend was observed at the most productive station (A3-2) where %DOC AA decreased from ~ 2% in the surface waters to 0.9% near 300 m. These AA yields revealed that POM and DOM were more rapidly altered or mineralized at the bloom sites compared to the HNLC site. Alteration state was also assessed by trends in C / N ratio, %D-AA and degradation index. Different molecular markers indicated that POM mostly originated from diatoms and bacteria. The estimated average proportion of POM from intact phytoplankton cells in surface waters was 45% at the bloom station A3-2, but 14% at the HNLC site. Estimates based on D-AA yields indicated that ~ 15% of POM and ~ 30% of DOM was of bacterial origin (cells and cell fragments) at all stations. Surprisingly, the DOM in HNLC waters appeared less altered than the DOM from the bloom, had slightly higher dissolved AA concentrations, and showed no sign of alteration within the water column. Unfavorable conditions for bacterial degradation in HNLC regions can explain these findings. In contrast, large inputs of labile organic molecules and iron likely stimulate the degradation of organic matter (priming effect) and the production of more recalcitrant DOM (microbial carbon pump) during iron-fertilized blooms. Article in Journal/Newspaper Kerguelen Islands Southern Ocean Directory of Open Access Journals: DOAJ Articles Southern Ocean Kerguelen Kerguelen Islands Biogeosciences 12 2 607 621 |
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 L. Tremblay J. Caparros K. Leblanc I. Obernosterer Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean |
topic_facet |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 |
description |
Natural iron fertilization of high-nutrient low-chlorophyll (HNLC) waters induces annually occurring spring phytoplankton blooms off the Kerguelen Islands (Southern Ocean). To examine the origin and fate of particulate and dissolved organic matter (POM and DOM), D- and L-amino acids (AA) were quantified at bloom and HNLC stations. Total hydrolyzable AA accounted for 21–25% of surface particulate organic carbon (%POC AA ) at the bloom sites, but for 10% at the HNLC site. A marked decrease in %POC AA with depth was observed at the most productive stations leading to values between 3 and 5% below 300 m depth. AA contributed to only 0.9–4.4% of dissolved organic carbon (%DOC AA ) at all stations. The only consistent vertical trend was observed at the most productive station (A3-2) where %DOC AA decreased from ~ 2% in the surface waters to 0.9% near 300 m. These AA yields revealed that POM and DOM were more rapidly altered or mineralized at the bloom sites compared to the HNLC site. Alteration state was also assessed by trends in C / N ratio, %D-AA and degradation index. Different molecular markers indicated that POM mostly originated from diatoms and bacteria. The estimated average proportion of POM from intact phytoplankton cells in surface waters was 45% at the bloom station A3-2, but 14% at the HNLC site. Estimates based on D-AA yields indicated that ~ 15% of POM and ~ 30% of DOM was of bacterial origin (cells and cell fragments) at all stations. Surprisingly, the DOM in HNLC waters appeared less altered than the DOM from the bloom, had slightly higher dissolved AA concentrations, and showed no sign of alteration within the water column. Unfavorable conditions for bacterial degradation in HNLC regions can explain these findings. In contrast, large inputs of labile organic molecules and iron likely stimulate the degradation of organic matter (priming effect) and the production of more recalcitrant DOM (microbial carbon pump) during iron-fertilized blooms. |
format |
Article in Journal/Newspaper |
author |
L. Tremblay J. Caparros K. Leblanc I. Obernosterer |
author_facet |
L. Tremblay J. Caparros K. Leblanc I. Obernosterer |
author_sort |
L. Tremblay |
title |
Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean |
title_short |
Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean |
title_full |
Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean |
title_fullStr |
Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean |
title_full_unstemmed |
Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean |
title_sort |
origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the southern ocean |
publisher |
Copernicus Publications |
publishDate |
2015 |
url |
https://doi.org/10.5194/bg-12-607-2015 https://doaj.org/article/6782daa95e6e4ccb8b208fcb51cd6e77 |
geographic |
Southern Ocean Kerguelen Kerguelen Islands |
geographic_facet |
Southern Ocean Kerguelen Kerguelen Islands |
genre |
Kerguelen Islands Southern Ocean |
genre_facet |
Kerguelen Islands Southern Ocean |
op_source |
Biogeosciences, Vol 12, Iss 2, Pp 607-621 (2015) |
op_relation |
http://www.biogeosciences.net/12/607/2015/bg-12-607-2015.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 1726-4170 1726-4189 doi:10.5194/bg-12-607-2015 https://doaj.org/article/6782daa95e6e4ccb8b208fcb51cd6e77 |
op_doi |
https://doi.org/10.5194/bg-12-607-2015 |
container_title |
Biogeosciences |
container_volume |
12 |
container_issue |
2 |
container_start_page |
607 |
op_container_end_page |
621 |
_version_ |
1766055408609263616 |