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Inorganic carbon uptake by Southern Ocean phytoplankton
Author(s) -
Tortell Philippe D.,
Payne Chris,
Gueguen Celine,
Strzepek Robert F.,
Boyd Philip W.,
Rost Björn
Publication year - 2008
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2008.53.4.1266
Subject(s) - phytoplankton , diatom , total inorganic carbon , oceanography , chlorophyll a , environmental chemistry , algae , seawater , incubation , biology , ecology , chemistry , botany , nutrient , carbon dioxide , geology , biochemistry
We report the results of laboratory and field studies examining inorganic carbon (C i ) utilization by Southern Ocean phytoplankton. Both in monospecific laboratory cultures of diatoms and Phaeocystis antarctica and in natural assemblages in the Ross Sea, C i uptake by phytoplankton was dominated by direct HCO 3 1 transport. The contribution of HCO 3 1 transport to total C i uptake ranged from 65% to 95%, with an overall average of ∼80%. There was no significant difference among diatoms and Phaeocystis in the extent of HCO 3 1 transport. Extracellular carbonic anhydrase activity (eCA) was detected in eight of nine laboratory phytoplankton cultures and in all natural assemblages in the Ross Sea. The effective catalytic enhancement of HCO 3 1 : CO 2 interconversion ranged from 1.5‐ to 13‐fold (overall mean ∼4‐fold). Diatom‐dominated Ross Sea assemblages had significantly greater eCA levels than did Phaeocystis‐dominated assemblages. We found no strong correlations between C i uptake parameters and in situ CO 2 concentrations or chlorophyll a levels in the Ross Sea assemblages. Incubation experiments with natural assemblages showed that HCO 3 1 uptake and eCA expression did not change significantly over an 8‐fold range in pCO 2 (10.1‐81.1 Pa), although total short‐term C fixation rates increased under low CO 2 conditions. Carbon‐concentrating mechanisms are widespread among Southern Ocean phytoplankton and constitutively expressed by natural assemblages in the Ross Sea.