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Seasonal changes in plankton respiration and bacterial metabolism in a temperate shelf sea

Seasonal changes in plankton respiration and bacterial metabolism in a temperate shelf sea
Seasonal changes in plankton respiration and bacterial metabolism in a temperate shelf sea
The seasonal variability of plankton metabolism indicates how much carbon is cycling within a system, as well as its capacity to store carbon or export organic matter and CO2 to the deep ocean. Seasonal variability between November 2014, April 2015 and July 2015 in plankton respiration and bacterial (Bacteria + Archaea) metabolism is reported for the upper and bottom mixing layers at two stations in the Celtic Sea, UK. Upper mixing layer (UML, >75 m in November, 41–70 m in April and ∼50 m in July) depth-integrated plankton metabolism showed strong seasonal changes with a maximum in April for plankton respiration (1.2- to 2-fold greater compared to November and July, respectively) and in July for bacterial production (2-fold greater compared to November and April). However UML depth-integrated bacterial respiration was similar in November and April and 2-fold lower in July. The greater variability in bacterial production compared to bacterial respiration drove seasonal changes in bacterial growth efficiencies, which had maximum values of 89% in July and minimum values of 5% in November. Rates of respiration and gross primary production (14C-PP) also showed different seasonal patterns, resulting in seasonal changes in 14C-PP:CRO2 ratios. In April, the system was net autotrophic (14C-PP:CRO2 > 1), with a surplus of organic matter available for higher trophic levels and export, while in July balanced metabolism occurred (14C-PP:CRO2 = 1) due to an increase in plankton respiration and a decrease in gross primary production. Comparison of the UML and bottom mixing layer indicated that plankton respiration and bacterial production were higher (between 4 and 8-fold and 4 and 7-fold, respectively) in the UML than below. However, the rates of bacterial respiration were not statistically different (p > .05) between the two mixing layers in any of the three sampled seasons. These results highlight that, contrary to previous data from shelf seas, the production of CO2 by the plankton community in the UML, which is then available to degas to the atmosphere, is greater than the respiratory production of dissolved inorganic carbon in deeper waters, which may contribute to offshore export
Plankton community respiration; , Bacterial production
0079-6611
1-13
García-Martín, E. Elena
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Daniels, Chris J.
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Davidson, Keith
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Davis, Clare E.
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Mahaffey, Claire
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Mayers, Kyle M.J.
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McNeill, Sharon
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Poulton, Alex J.
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Purdie, Duncan
18820b32-185a-467a-8019-01f245191cd8
Tarran, Glen A.
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Robinson, Carol
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García-Martín, E. Elena
9ef13e0f-4797-4ac3-ac8b-94522bbc4c56
Daniels, Chris J.
aec2572b-e302-4f8e-ab7a-86b8bdf1c155
Davidson, Keith
a7b8cf91-5373-469f-a60b-23c43f355b2c
Davis, Clare E.
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Mahaffey, Claire
6c868a01-2c9b-48b0-ae08-9ecf6b870032
Mayers, Kyle M.J.
9841ee5d-63fb-441e-a5e7-5b611468723d
McNeill, Sharon
c88b196f-05e4-4a50-9441-1782b5c2a98a
Poulton, Alex J.
14bf64a7-d617-4913-b882-e8495543e717
Purdie, Duncan
18820b32-185a-467a-8019-01f245191cd8
Tarran, Glen A.
218a9233-a6ae-4d0c-a9ca-35ad0d5a35f7
Robinson, Carol
aa5b407d-ce1d-4706-a7ce-e2ee4c832071

García-Martín, E. Elena, Daniels, Chris J., Davidson, Keith, Davis, Clare E., Mahaffey, Claire, Mayers, Kyle M.J., McNeill, Sharon, Poulton, Alex J., Purdie, Duncan, Tarran, Glen A. and Robinson, Carol (2017) Seasonal changes in plankton respiration and bacterial metabolism in a temperate shelf sea. Progress in Oceanography, 1-13. (doi:10.1016/j.pocean.2017.12.002).

Record type: Article

Abstract

The seasonal variability of plankton metabolism indicates how much carbon is cycling within a system, as well as its capacity to store carbon or export organic matter and CO2 to the deep ocean. Seasonal variability between November 2014, April 2015 and July 2015 in plankton respiration and bacterial (Bacteria + Archaea) metabolism is reported for the upper and bottom mixing layers at two stations in the Celtic Sea, UK. Upper mixing layer (UML, >75 m in November, 41–70 m in April and ∼50 m in July) depth-integrated plankton metabolism showed strong seasonal changes with a maximum in April for plankton respiration (1.2- to 2-fold greater compared to November and July, respectively) and in July for bacterial production (2-fold greater compared to November and April). However UML depth-integrated bacterial respiration was similar in November and April and 2-fold lower in July. The greater variability in bacterial production compared to bacterial respiration drove seasonal changes in bacterial growth efficiencies, which had maximum values of 89% in July and minimum values of 5% in November. Rates of respiration and gross primary production (14C-PP) also showed different seasonal patterns, resulting in seasonal changes in 14C-PP:CRO2 ratios. In April, the system was net autotrophic (14C-PP:CRO2 > 1), with a surplus of organic matter available for higher trophic levels and export, while in July balanced metabolism occurred (14C-PP:CRO2 = 1) due to an increase in plankton respiration and a decrease in gross primary production. Comparison of the UML and bottom mixing layer indicated that plankton respiration and bacterial production were higher (between 4 and 8-fold and 4 and 7-fold, respectively) in the UML than below. However, the rates of bacterial respiration were not statistically different (p > .05) between the two mixing layers in any of the three sampled seasons. These results highlight that, contrary to previous data from shelf seas, the production of CO2 by the plankton community in the UML, which is then available to degas to the atmosphere, is greater than the respiratory production of dissolved inorganic carbon in deeper waters, which may contribute to offshore export

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Garcia-Martin et al. Seasonal variability SSB_reviewedManuscript_submitted - Accepted Manuscript
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Accepted/In Press date: 8 December 2017
e-pub ahead of print date: 8 December 2017
Keywords: Plankton community respiration; , Bacterial production

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Local EPrints ID: 416696
URI: https://eprints.soton.ac.uk/id/eprint/416696
ISSN: 0079-6611
PURE UUID: 3c174da5-8740-4879-ad4b-cf853dcc60d6

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Date deposited: 05 Jan 2018 17:30
Last modified: 09 Dec 2019 18:27

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Contributors

Author: E. Elena García-Martín
Author: Chris J. Daniels
Author: Keith Davidson
Author: Clare E. Davis
Author: Claire Mahaffey
Author: Kyle M.J. Mayers
Author: Sharon McNeill
Author: Alex J. Poulton
Author: Duncan Purdie
Author: Glen A. Tarran
Author: Carol Robinson

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