Chemometric perspectives on plankton community responses to natural iron fertilisation over and downstream of the Kerguelen Plateau in the Southern Ocean
We examined phytoplankton community responses to natural iron fertilisation at 32 sites over and downstream from the Kerguelen Plateau in the Southern Ocean during the austral spring bloom in October–November 2011. The community structure was estimated from chemical and isotopic measurements (partic...
| Main Authors: | , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2015-02-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/12/1029/2015/bg-12-1029-2015.pdf |
| _version_ | 1811225280027557888 |
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| author | T. W. Trull D. M. Davies F. Dehairs A.-J. Cavagna M. Lasbleiz E. C. Laurenceau-Cornec F. d'Ovidio F. Planchon K. Leblanc B. Quéguiner S. Blain |
| author_facet | T. W. Trull D. M. Davies F. Dehairs A.-J. Cavagna M. Lasbleiz E. C. Laurenceau-Cornec F. d'Ovidio F. Planchon K. Leblanc B. Quéguiner S. Blain |
| author_sort | T. W. Trull |
| collection | DOAJ |
| description | We examined phytoplankton community responses to natural iron fertilisation
at 32 sites over and downstream from the Kerguelen Plateau in the Southern
Ocean during the austral spring bloom in October–November 2011. The community
structure was estimated from chemical and isotopic measurements (particulate
organic carbon – POC; <sup>13</sup>C-POC; particulate nitrogen – PN; <sup>15</sup>N-PN; and
biogenic silica – BSi) on size-fractionated samples from surface waters (300,
210, 50, 20, 5, and 1 μm fractions). Higher values of <sup>13</sup>C-POC (vs.
co-located <sup>13</sup>C values for dissolved inorganic carbon – DIC) were taken
as indicative of faster growth rates and higher values of <sup>15</sup>N-PN (vs.
co-located <sup>15</sup>N-NO<sub>3</sub> source values) as indicative of greater nitrate
use (rather than ammonium use, i.e. higher <i>f</i> ratios).
<br><br>
Community responses varied in relation to both regional circulation and the
advance of the bloom. Iron-fertilised waters over the plateau developed
dominance by very large diatoms (50–210 μm) with high BSi / POC ratios,
high growth rates, and significant ammonium recycling (lower <i>f</i> ratios) as
biomass built up. In contrast, downstream polar frontal waters with a similar
or higher iron supply were dominated by smaller diatoms (20–50 μm)
and exhibited greater ammonium recycling. Stations in a deep-water
bathymetrically trapped recirculation south of the polar front with lower
iron levels showed the large-cell dominance observed on the plateau but
much less biomass. Comparison of these communities to surface water nitrate
(and silicate) depletions as a proxy for export shows that the low-biomass
recirculation feature had exported similar amounts of nitrogen to the high-biomass blooms over the plateau and north of the polar front. This suggests
that early spring trophodynamic and export responses differed between
regions with persistent low levels vs. intermittent high levels of iron
fertilisation. |
| first_indexed | 2024-04-12T09:03:11Z |
| format | Article |
| id | doaj.art-f87893b7016141e79814e45242e8c3e9 |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-04-12T09:03:11Z |
| publishDate | 2015-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-f87893b7016141e79814e45242e8c3e92022-12-22T03:39:10ZengCopernicus PublicationsBiogeosciences1726-41701726-41892015-02-011241029105610.5194/bg-12-1029-2015Chemometric perspectives on plankton community responses to natural iron fertilisation over and downstream of the Kerguelen Plateau in the Southern OceanT. W. Trull0D. M. Davies1F. Dehairs2A.-J. Cavagna3M. Lasbleiz4E. C. Laurenceau-Cornec5F. d'Ovidio6F. Planchon7K. Leblanc8B. Quéguiner9S. Blain10CSIRO Marine and Atmospheric Research, Hobart, Tasmania, AustraliaCSIRO Marine and Atmospheric Research, Hobart, Tasmania, AustraliaInstitute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, AustraliaAnalytical, Environmental and Geochemistry; Earth Sciences Research Group, Vrije Universiteit Brussel, BelgiumAix-Marseille Université and Université de Toulon, Marseille, FranceCSIRO Marine and Atmospheric Research, Hobart, Tasmania, AustraliaLOCEAN–IPSL, Université Pierre et Marie Curie, Paris, FranceLaboratoire des Sciences de l'Environnement Marin (LEMAR), Université de Brest, IUEM, Plouzané, FranceAix-Marseille Université and Université de Toulon, Marseille, FranceAix-Marseille Université and Université de Toulon, Marseille, FranceSorbonne Universités, UPMC Univ Paris 06, UMR7621, Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, 66650 Banyuls/mer, FranceWe examined phytoplankton community responses to natural iron fertilisation at 32 sites over and downstream from the Kerguelen Plateau in the Southern Ocean during the austral spring bloom in October–November 2011. The community structure was estimated from chemical and isotopic measurements (particulate organic carbon – POC; <sup>13</sup>C-POC; particulate nitrogen – PN; <sup>15</sup>N-PN; and biogenic silica – BSi) on size-fractionated samples from surface waters (300, 210, 50, 20, 5, and 1 μm fractions). Higher values of <sup>13</sup>C-POC (vs. co-located <sup>13</sup>C values for dissolved inorganic carbon – DIC) were taken as indicative of faster growth rates and higher values of <sup>15</sup>N-PN (vs. co-located <sup>15</sup>N-NO<sub>3</sub> source values) as indicative of greater nitrate use (rather than ammonium use, i.e. higher <i>f</i> ratios). <br><br> Community responses varied in relation to both regional circulation and the advance of the bloom. Iron-fertilised waters over the plateau developed dominance by very large diatoms (50–210 μm) with high BSi / POC ratios, high growth rates, and significant ammonium recycling (lower <i>f</i> ratios) as biomass built up. In contrast, downstream polar frontal waters with a similar or higher iron supply were dominated by smaller diatoms (20–50 μm) and exhibited greater ammonium recycling. Stations in a deep-water bathymetrically trapped recirculation south of the polar front with lower iron levels showed the large-cell dominance observed on the plateau but much less biomass. Comparison of these communities to surface water nitrate (and silicate) depletions as a proxy for export shows that the low-biomass recirculation feature had exported similar amounts of nitrogen to the high-biomass blooms over the plateau and north of the polar front. This suggests that early spring trophodynamic and export responses differed between regions with persistent low levels vs. intermittent high levels of iron fertilisation.http://www.biogeosciences.net/12/1029/2015/bg-12-1029-2015.pdf |
| spellingShingle | T. W. Trull D. M. Davies F. Dehairs A.-J. Cavagna M. Lasbleiz E. C. Laurenceau-Cornec F. d'Ovidio F. Planchon K. Leblanc B. Quéguiner S. Blain Chemometric perspectives on plankton community responses to natural iron fertilisation over and downstream of the Kerguelen Plateau in the Southern Ocean Biogeosciences |
| title | Chemometric perspectives on plankton community responses to natural iron fertilisation over and downstream of the Kerguelen Plateau in the Southern Ocean |
| title_full | Chemometric perspectives on plankton community responses to natural iron fertilisation over and downstream of the Kerguelen Plateau in the Southern Ocean |
| title_fullStr | Chemometric perspectives on plankton community responses to natural iron fertilisation over and downstream of the Kerguelen Plateau in the Southern Ocean |
| title_full_unstemmed | Chemometric perspectives on plankton community responses to natural iron fertilisation over and downstream of the Kerguelen Plateau in the Southern Ocean |
| title_short | Chemometric perspectives on plankton community responses to natural iron fertilisation over and downstream of the Kerguelen Plateau in the Southern Ocean |
| title_sort | chemometric perspectives on plankton community responses to natural iron fertilisation over and downstream of the kerguelen plateau in the southern ocean |
| url | http://www.biogeosciences.net/12/1029/2015/bg-12-1029-2015.pdf |
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