1266-1278 Tortell.pdf (601.6 kB)
Inorganic carbon uptake by Southern Ocean phytoplankton
journal contributionposted on 2023-05-18, 04:00 authored by Tortell, PD, Payne, C, Gueguen, C, Robert StrzepekRobert Strzepek, Philip BoydPhilip Boyd, Rost, B
We report the results of laboratory and field studies examining inorganic carbon (Ci) utilization by Southern Ocean phytoplankton. Both in monospecific laboratory cultures of diatoms and Phaeocystis antarctica and in natural assemblages in the Ross Sea, Ci uptake by phytoplankton was dominated by direct HCO31 transport. The contribution of HCO31 transport to total Ci 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 HCO31 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 HCO31 : CO2 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 Ci uptake parameters and in situ CO2 concentrations or chlorophyll a levels in the Ross Sea assemblages. Incubation experiments with natural assemblages showed that HCO31 uptake and eCA expression did not change significantly over an 8-fold range in pCO2 (10.1-81.1 Pa), although total short-term C fixation rates increased under low CO2 conditions. Carbon-concentrating mechanisms are widespread among Southern Ocean phytoplankton and constitutively expressed by natural assemblages in the Ross Sea.
Publication titleLimnology and Oceanography
Department/SchoolInstitute for Marine and Antarctic Studies
PublisherAmer Soc Limnology Oceanography
Place of publication5400 Bosque Blvd, Ste 680, Waco, USA, Tx, 76710-4446
Rights statementCopyright 2008 The American Society of Limnology and Oceanography Inc.