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Significance of the Polar Frontal Zone for large-sized diatoms and new production during summer in the Atlantic sector of the Southern Ocean

Significance of the Polar Frontal Zone for large-sized diatoms and new production during summer in the Atlantic sector of the Southern Ocean
Significance of the Polar Frontal Zone for large-sized diatoms and new production during summer in the Atlantic sector of the Southern Ocean
The chlorophyll a (chl a) biomass and primary production of three phytoplankton size fractions were estimated in the Atlantic sector of the Southern Ocean from 12 December 1995 to 20 January 1996. Elevated concentrations of chl a, primary production, and contribution of microplankton (>20 ?m) coincided with dominance by large or long-chained diatoms (Thalassiothrix spp., Pseudonitzschia lineola, and Chaetoceros spp.) in the Polar Frontal Zone (PFZ, 49.5°S–52°S). Vertically resolved assimilation numbers (i.e. primary production normalized to chl a) and intrinsic growth rates of microplankton were much lower at high-biomass stations of the Northern Polar Frontal Zone (NPFZ) than in adjacent waters. Silicic acid appeared to be the proximal factor limiting the growth and yield of resident diatoms in the NPFZ. A carbon budget showed that, during the sampling period, diatom dominance at high-biomass sites was associated with near-steady-state conditions. This system exhibited a low POC sinking flux relative to total primary production, despite strong dominance by microplankton. South of 52°S, total chl a and primary production were generally low, but increased sharply in a mixed Phaeocystis-diatom bloom that extended from 61°S to 65°S in the Seasonal Ice Zone (SIZ). We estimated that the PFZ contributes from 37% to 67% of the total open-water new production in the Southern Ocean near the Greenwich meridian, depending on whether blooms occur or not in the SIZ.
0967-0645
3793-3811
Tremblay, J.E.
a8e2894c-9d36-42ea-a844-95d2de5548fa
Lucas, M.I.
1d860b0b-ec20-428d-afaa-0f5ca576e369
Kattner, G.
cce82d92-3692-436a-be7b-8fdb71895b57
Pollard, R.T.
0c78b909-8a95-4bd2-82fd-9b11022888fd
Strass, V.H.
ffd244f4-43d0-4916-a063-7008231cdf5e
Bathmann, U.V.
6411fbb4-02bc-44be-88e9-23be8ef2f6f9
Bracher, A.
70390c2b-bb78-4006-8f53-ea1c0a494646
Tremblay, J.E.
a8e2894c-9d36-42ea-a844-95d2de5548fa
Lucas, M.I.
1d860b0b-ec20-428d-afaa-0f5ca576e369
Kattner, G.
cce82d92-3692-436a-be7b-8fdb71895b57
Pollard, R.T.
0c78b909-8a95-4bd2-82fd-9b11022888fd
Strass, V.H.
ffd244f4-43d0-4916-a063-7008231cdf5e
Bathmann, U.V.
6411fbb4-02bc-44be-88e9-23be8ef2f6f9
Bracher, A.
70390c2b-bb78-4006-8f53-ea1c0a494646

Tremblay, J.E., Lucas, M.I., Kattner, G., Pollard, R.T., Strass, V.H., Bathmann, U.V. and Bracher, A. (2002) Significance of the Polar Frontal Zone for large-sized diatoms and new production during summer in the Atlantic sector of the Southern Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 49 (18), 3793-3811. (doi:10.1016/S0967-0645(02)00111-X).

Record type: Article

Abstract

The chlorophyll a (chl a) biomass and primary production of three phytoplankton size fractions were estimated in the Atlantic sector of the Southern Ocean from 12 December 1995 to 20 January 1996. Elevated concentrations of chl a, primary production, and contribution of microplankton (>20 ?m) coincided with dominance by large or long-chained diatoms (Thalassiothrix spp., Pseudonitzschia lineola, and Chaetoceros spp.) in the Polar Frontal Zone (PFZ, 49.5°S–52°S). Vertically resolved assimilation numbers (i.e. primary production normalized to chl a) and intrinsic growth rates of microplankton were much lower at high-biomass stations of the Northern Polar Frontal Zone (NPFZ) than in adjacent waters. Silicic acid appeared to be the proximal factor limiting the growth and yield of resident diatoms in the NPFZ. A carbon budget showed that, during the sampling period, diatom dominance at high-biomass sites was associated with near-steady-state conditions. This system exhibited a low POC sinking flux relative to total primary production, despite strong dominance by microplankton. South of 52°S, total chl a and primary production were generally low, but increased sharply in a mixed Phaeocystis-diatom bloom that extended from 61°S to 65°S in the Seasonal Ice Zone (SIZ). We estimated that the PFZ contributes from 37% to 67% of the total open-water new production in the Southern Ocean near the Greenwich meridian, depending on whether blooms occur or not in the SIZ.

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Published date: 2002

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Local EPrints ID: 63100
URI: http://eprints.soton.ac.uk/id/eprint/63100
ISSN: 0967-0645
PURE UUID: 669c4670-76f1-4a4c-b431-a109d22ced65

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Date deposited: 10 Sep 2008
Last modified: 15 Mar 2024 11:34

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Author: J.E. Tremblay
Author: M.I. Lucas
Author: G. Kattner
Author: R.T. Pollard
Author: V.H. Strass
Author: U.V. Bathmann
Author: A. Bracher

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