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Microzooplankton regulation of surface ocean POC:PON ratios

Microzooplankton regulation of surface ocean POC:PON ratios
Microzooplankton regulation of surface ocean POC:PON ratios
The elemental composition of particulate organic matter in the surface ocean significantly affects the efficiency of the ocean's store of carbon. Though the elemental composition of primary producers is an important factor, recent observations from the western North Atlantic Ocean revealed that carbon-to-nitrogen ratios (C:N) of phytoplankton were significantly higher than the relatively homeostatic ratio of the total particulate pool (particulate organic carbon:particulate organic nitrogen; POC:PON). Here we use an idealized ecosystem model to show how interactions between primary and secondary producers maintain the mean composition of surface particulates and the difference between primary producers and bulk material. Idealized physiological models of phytoplankton and microzooplankton, constrained by laboratory data, reveal contrasting autotrophic and heterotrophic responses to nitrogen limitation: under nitrogen limitation, phytoplankton accumulate carbon in carbohydrates and lipids while microzooplankton deplete internal C reserves to fuel respiration. Global ecosystem simulations yield hypothetical global distributions of phytoplankton and microzooplankton C:N ratio predicting elevated phytoplankton C:N ratios in the high-light, low-nutrient regions of the ocean despite a lower, homeostatic POC:PON ratio due to respiration of excess carbon in systems subject to top-down control. The model qualitatively captures and provides a simple interpretation for, a global compilation of surface ocean POC:PON data.
phytoplankton, stoichiometry, redfield, biological carbon pump, microzooplankton, ecosystem model
0886-6236
311-332
Talmy, D.
4be29c52-7091-4c7d-a793-94013351c558
Martiny, A.C.
4e665eb2-c350-4ea4-b64a-20d4d825a188
Hill, C.
f8e9fa28-fd5a-4ad1-9c1d-b1acd846c94e
Hickman, A.E.
a99786c6-65e6-48c8-8b58-0d3b5608be92
Follows, M.J.
b2eaa10d-93af-421a-a37a-5a1e446360b3
Talmy, D.
4be29c52-7091-4c7d-a793-94013351c558
Martiny, A.C.
4e665eb2-c350-4ea4-b64a-20d4d825a188
Hill, C.
f8e9fa28-fd5a-4ad1-9c1d-b1acd846c94e
Hickman, A.E.
a99786c6-65e6-48c8-8b58-0d3b5608be92
Follows, M.J.
b2eaa10d-93af-421a-a37a-5a1e446360b3

Talmy, D., Martiny, A.C., Hill, C., Hickman, A.E. and Follows, M.J. (2016) Microzooplankton regulation of surface ocean POC:PON ratios. Global Biogeochemical Cycles, 30 (2), 311-332. (doi:10.1002/2015GB005273).

Record type: Article

Abstract

The elemental composition of particulate organic matter in the surface ocean significantly affects the efficiency of the ocean's store of carbon. Though the elemental composition of primary producers is an important factor, recent observations from the western North Atlantic Ocean revealed that carbon-to-nitrogen ratios (C:N) of phytoplankton were significantly higher than the relatively homeostatic ratio of the total particulate pool (particulate organic carbon:particulate organic nitrogen; POC:PON). Here we use an idealized ecosystem model to show how interactions between primary and secondary producers maintain the mean composition of surface particulates and the difference between primary producers and bulk material. Idealized physiological models of phytoplankton and microzooplankton, constrained by laboratory data, reveal contrasting autotrophic and heterotrophic responses to nitrogen limitation: under nitrogen limitation, phytoplankton accumulate carbon in carbohydrates and lipids while microzooplankton deplete internal C reserves to fuel respiration. Global ecosystem simulations yield hypothetical global distributions of phytoplankton and microzooplankton C:N ratio predicting elevated phytoplankton C:N ratios in the high-light, low-nutrient regions of the ocean despite a lower, homeostatic POC:PON ratio due to respiration of excess carbon in systems subject to top-down control. The model qualitatively captures and provides a simple interpretation for, a global compilation of surface ocean POC:PON data.

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Accepted/In Press date: 11 January 2016
e-pub ahead of print date: 23 February 2016
Published date: February 2016
Keywords: phytoplankton, stoichiometry, redfield, biological carbon pump, microzooplankton, ecosystem model
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 388362
URI: http://eprints.soton.ac.uk/id/eprint/388362
ISSN: 0886-6236
PURE UUID: fc573c25-4b52-414a-85d0-bd3d6dbf6300
ORCID for A.E. Hickman: ORCID iD orcid.org/0000-0002-2774-3934

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Date deposited: 24 Feb 2016 11:07
Last modified: 28 Apr 2022 02:07

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Contributors

Author: D. Talmy
Author: A.C. Martiny
Author: C. Hill
Author: A.E. Hickman ORCID iD
Author: M.J. Follows

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