Inorganic carbon uptake by an Antarctic sea-ice diatom,Nitzschia frigida |
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Authors: | C Mitchell J Beardall |
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Institution: | (1) School of Botany, University of Melbourne, 3001 Parkville, Victoria, Australia;(2) Department of Ecology and Evolutionary Biology, Monash University, 3168 Clayton, Victoria, Australia;(3) Present address: CSIRO Division of Atmospheric Research, Private Bag #1, 3195 Mordialloc, Victoria, Australia |
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Abstract: | There have been no studies to date on the mechanisms of inorganic carbon acquisition by Antarctic microalgae. Consequently,
we have examined inorganic carbon (DIC) use in Nitzschia frigida, a diatom typical of the Antarctic bottom-ice community. The K0.5 (CO2) of photosynthesis in this organism was estimated to be 1.09 μM at pH 7.5. The internal concentration of DIC was approximately
4050 μM at an external DIC] of 45 μM. At air-equilibration levels of inorganic carbon this would be sufficient for a ten-fold
accumulation ratio of CO2. Cells of N. frigida are capable of carbon-dependent photosynthesis at rates that exceed that expected from uncatalysed CO2 supply to the cell. About 25% of the total carbonic anhydrase activity appears to be associated with the cell surface in
N. frigida. These results support the hypothesis that N. frigida, like many microalgae from temperate waters, has an active carbon-concentrating mechanism, associated with the ability to
utilize external HCO-
3 for photosynthesis.
Received: 12 September 1994/Accepted: 8 May 1995 |
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