Copepods boost the production but reduce the carbon export efficiency by diatoms
Copepods boost the production but reduce the carbon export efficiency by diatoms
The fraction of net primary production that is exported from the euphotic zone as sinking particulate organic carbon (POC) varies notably through time and from region to region. Phytoplankton containing biominerals, such as silicified diatoms have long been associated with high export fluxes. However, recent reviews point out that the magnitude of export is not controlled by diatoms alone, but determined by the whole plankton community structure. The combined effect of phytoplankton community composition and zooplankton abundance on export flux dynamics, were explored using a set of 12 large outdoor mesocosms. All mesocosms received a daily addition of minor amounts of nitrate and phosphate, while only 6 mesocosms received silicic acid (dSi). This resulted in a dominance of diatoms and dinoflagellate in the +Si mesocosms and a dominance of dinoflagellate in the -Si mesocosms. Simultaneously, half of the mesocosms had decreased mesozooplankton populations whereas the other half were supplemented with additional zooplankton. In all mesocosms, POC fluxes were positively correlated to Si/C ratios measured in the surface community and additions of dSi globally increased the export fluxes in all treatments highlighting the role of diatoms in C export. The presence of additional copepods resulted in higher standing stocks of POC, most probably through trophic cascades. However it only resulted in higher export fluxes for the -Si mesocosms. In the +Si with copepod addition (+Si +Cops) export was dominated by large diatoms with higher Si/C ratios in sinking material than in standing stocks. During non-bloom situations, the grazing activity of copepods decrease the export efficiency in diatom dominated systems by changing the structure of the phytoplankton community and/or preventing their aggregation. However, in flagellate-dominated system, the copepods increased phytoplankton growth, aggregation and fecal pellet production, with overall higher net export not always visible in term of export efficiency.
Bay of Hopavågen, Biogenic silica, Biological pump, Marine snow, Mesocosm, Plankton community, POC, Zooplankton
Moriceau, Brivaëla
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Iversen, Morten H.
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Gallinari, Morgane
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Evertsen, Antti Jussi O.
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Le Goff, Manon
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Beker, Beatriz
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Boutorh, Julia
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Corvaisier, Rudolph
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Coffineau, Nathalie
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Donval, Anne
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Giering, Sarah L.C.
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Koski, Marja
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Lambert, Christophe
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Lampitt, Richard S.
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Le Mercier, Alain
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Masson, Annick
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Stibor, Herwig
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Stockenreiter, Maria
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De La Rocha, Christina L.
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Moriceau, Brivaëla
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Iversen, Morten H.
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Gallinari, Morgane
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Evertsen, Antti Jussi O.
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Le Goff, Manon
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Beker, Beatriz
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Boutorh, Julia
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Corvaisier, Rudolph
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Coffineau, Nathalie
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Donval, Anne
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Giering, Sarah L.C.
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Koski, Marja
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Lambert, Christophe
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Lampitt, Richard S.
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Le Mercier, Alain
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Masson, Annick
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Stibor, Herwig
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Stockenreiter, Maria
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De La Rocha, Christina L.
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Moriceau, Brivaëla, Iversen, Morten H., Gallinari, Morgane, Evertsen, Antti Jussi O., Le Goff, Manon, Beker, Beatriz, Boutorh, Julia, Corvaisier, Rudolph, Coffineau, Nathalie, Donval, Anne, Giering, Sarah L.C., Koski, Marja, Lambert, Christophe, Lampitt, Richard S., Le Mercier, Alain, Masson, Annick, Stibor, Herwig, Stockenreiter, Maria and De La Rocha, Christina L.
(2018)
Copepods boost the production but reduce the carbon export efficiency by diatoms.
Frontiers in Marine Science, 5 (MAR), [82].
(doi:10.3389/fmars.2018.00082).
Abstract
The fraction of net primary production that is exported from the euphotic zone as sinking particulate organic carbon (POC) varies notably through time and from region to region. Phytoplankton containing biominerals, such as silicified diatoms have long been associated with high export fluxes. However, recent reviews point out that the magnitude of export is not controlled by diatoms alone, but determined by the whole plankton community structure. The combined effect of phytoplankton community composition and zooplankton abundance on export flux dynamics, were explored using a set of 12 large outdoor mesocosms. All mesocosms received a daily addition of minor amounts of nitrate and phosphate, while only 6 mesocosms received silicic acid (dSi). This resulted in a dominance of diatoms and dinoflagellate in the +Si mesocosms and a dominance of dinoflagellate in the -Si mesocosms. Simultaneously, half of the mesocosms had decreased mesozooplankton populations whereas the other half were supplemented with additional zooplankton. In all mesocosms, POC fluxes were positively correlated to Si/C ratios measured in the surface community and additions of dSi globally increased the export fluxes in all treatments highlighting the role of diatoms in C export. The presence of additional copepods resulted in higher standing stocks of POC, most probably through trophic cascades. However it only resulted in higher export fluxes for the -Si mesocosms. In the +Si with copepod addition (+Si +Cops) export was dominated by large diatoms with higher Si/C ratios in sinking material than in standing stocks. During non-bloom situations, the grazing activity of copepods decrease the export efficiency in diatom dominated systems by changing the structure of the phytoplankton community and/or preventing their aggregation. However, in flagellate-dominated system, the copepods increased phytoplankton growth, aggregation and fecal pellet production, with overall higher net export not always visible in term of export efficiency.
Text
fmars-05-00082
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Accepted/In Press date: 26 February 2018
e-pub ahead of print date: 22 March 2018
Keywords:
Bay of Hopavågen, Biogenic silica, Biological pump, Marine snow, Mesocosm, Plankton community, POC, Zooplankton
Identifiers
Local EPrints ID: 419427
URI: http://eprints.soton.ac.uk/id/eprint/419427
ISSN: 2296-7745
PURE UUID: b0cb44f1-d6c7-46ec-95f2-702a52247996
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Date deposited: 12 Apr 2018 16:30
Last modified: 15 Mar 2024 19:22
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Contributors
Author:
Brivaëla Moriceau
Author:
Morten H. Iversen
Author:
Morgane Gallinari
Author:
Antti Jussi O. Evertsen
Author:
Manon Le Goff
Author:
Beatriz Beker
Author:
Julia Boutorh
Author:
Rudolph Corvaisier
Author:
Nathalie Coffineau
Author:
Anne Donval
Author:
Sarah L.C. Giering
Author:
Marja Koski
Author:
Christophe Lambert
Author:
Richard S. Lampitt
Author:
Alain Le Mercier
Author:
Annick Masson
Author:
Herwig Stibor
Author:
Maria Stockenreiter
Author:
Christina L. De La Rocha
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