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The relation of mixed-layer net community production to phytoplankton community composition in the Southern Ocean


Cassar, N and Wright, SW and Thomson, PG and Trull, TW and Westwood, KJ and de Salas, M and Davidson, A and Pearce, I and Davies, DM and Matear, RJ, The relation of mixed-layer net community production to phytoplankton community composition in the Southern Ocean, Global Biogeochemical Cycles, 29, (4) pp. 446-462. ISSN 0886-6236 (2015) [Refereed Article]


Copyright Statement

2015. American Geophysical Union. All Rights Reserved.

DOI: doi:10.1002/2014GB004936


Surface ocean productivity mediates the transfer of carbon to the deep ocean and in the process regulates atmospheric CO2 levels. A common axiom in oceanography is that large phytoplankton contribute disproportionally to the transfer of carbon to the deep ocean because of their greater ability to escape grazing pressure, build biomass, and sink. In the present study, we assessed the relationship of net community production to phytoplankton assemblages and plankton size distribution in the Sub-Antarctic Zone and northern reaches of the Polar Frontal Zone in the Australian sector of the Southern Ocean. We reanalyzed and synthesized previously published estimates of O2/Ar net community oxygen production (NCP) and triple-O2 isotopes gross primary oxygen production (GPP) along with microscopic and pigment analyses of the microbial community. Overall, we found that the axiom that large phytoplankton drive carbon export was not supported in this region. Mixed-layer-depth-integrated NCP was correlated to particulate organic carbon (POC) concentration in the mixed layer. While lower NCP/GPP and NCP/POC values were generally associated with communities dominated by smaller plankton size (as would be expected), these communities did not preclude high values for both properties. Vigorous NCP in some regions occurred in the virtual absence of large phytoplankton (and specifically diatoms) and in communities dominated by nanoplankton and picoplankton. We also observed a positive correlation between NCP and the proportion of the phytoplankton community grazed by microheterotrophs, supporting the mediating role of grazers in carbon export. The novel combination of techniques allowed us to determine how NCP relates to upper ocean ecosystem characteristics and may lead to improved models of carbon export.

Item Details

Item Type:Refereed Article
Keywords:phytoplankton, Southern Ocean, net community oxygen production, NCP
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical oceanography
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Antarctic and Southern Ocean oceanic processes
UTAS Author:Wright, SW (Dr Simon Wright)
UTAS Author:Trull, TW (Professor Thomas Trull)
UTAS Author:Westwood, KJ (Dr Karen Westwood)
UTAS Author:de Salas, M (Dr Miguel de Salas)
UTAS Author:Davidson, A (Dr Andrew Davidson)
UTAS Author:Pearce, I (Dr Imojen Pearce)
UTAS Author:Davies, DM (Ms Diana Davies)
ID Code:106056
Year Published:2015
Web of Science® Times Cited:27
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2016-01-27
Last Modified:2017-11-01
Downloads:182 View Download Statistics

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