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Export and isotropic composition of organic matter in the Subantarctic and polar frontal zones of the Southern Ocean

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Lourey, Martin John (2003) Export and isotropic composition of organic matter in the Subantarctic and polar frontal zones of the Southern Ocean. PhD thesis, University of Tasmania.

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Abstract

This thesis aims to improve estimates of net community production and carbon export in the
Subantarctic (SAZ) and Polar Frontal Zones (PFZ) of the Southern Ocean from estimates of nutrient
depletion, and to use measurements of stable isotopes in suspended and sinking organic matter to
assess ecosystem processes responsible for nitrate and CO2 depletion. Estimates of seasonal surface water nutrient depletion corrected for frontal movements and
changes in water masses using observed quasi-linear nutrient-salinity relationships, suggest that from
July to March nitrate depletion and carbon export in the SAZ (510 mmol N 111 -2 and 3,400 mmol
C m-2 ) was approximately twice that of the PFZ (250 mmol N m-2and 1,600 mmol C m -2 ).
Phosphate depletions were similar (29 and 24 mmol P m -2for the SAZ and PFZ, respectively)
between the regions due to a lower N/P ratio of depletion in the PFZ (8.3 ± 5.4) than the SAZ
(15.1 ± 2.3). Comparison with sediment trap and primary production estimates suggests that
differences in nitrate depletion are the result of differences in production. However, the relative
magnitude of export in the two zones remains uncertain because resupply of nutrients from the
south may lower the observed nutrient depletions in the PFZ. Only 2 to 3% of the material leaving
the surface reaches deep water sediment traps deployed at 800 to 1000 m, suggesting most organic
carbon is remineralised and its constituent nutrients and CO2 transported to lower latitudes in the
Antarctic Intermediate and Subantarctic Mode Waters.

Item Type: Thesis (PhD)
Keywords: Biogeochemical cycles, Carbon cycle (Biogeochemistry), Chemical oceanography, Ocean-atmosphere interaction, Nitrogen
Copyright Holders: The Author
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Copyright 2003 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 2003. Includes bibliographical references (117-139)

Date Deposited: 19 Dec 2014 02:45
Last Modified: 17 Jul 2017 07:51
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