Comparative studies of inorganic carbon utilization inEmiliania huxleyi and some non-calcifying marine microalgae |
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| Authors: | Dong Liang-feng M J Merrett Wu Chao-yuan |
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| Institution: | (1) Department of Biology, John Tabor Laboratory, University of Essex, Wivenhoe Park, Colchester, UK;(2) School of Biological Sciences, University of Wales Swansea, Singleton Park, Swansea, UK;(3) Department of Marine Botany, Institute of Oceanology, Chinese Academy of Sciences, 266071 Qingdao, China |
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| Abstract: | Inorganic carbon utilization in the non-calcifying marine microalgae,Nannochloropsis oculata, Phaeodactylum tricornutum andPorphyridium purpureum was compared with high- and low-calcifying strains ofEmiliania huxleyi grown in artificial seawater medium aerated with either air (0.03% V/V CO2) or CO2-free air. For high-calcifying strain ofE. oculata andP. tricornutem, similar growth patterns were observed in air-and CO2-free air-grown cultures.P. purpureum showed a less final cell density in CO2-free air than in air-grown culture. However, low-calcifying strain ofE. huxleyi was able to grow only in air-grown culture, but not in CO2-free air-grown culture.
Measurements of alkalinity, pH, concentration of dissolved inorganic carbon (DIC) and free CO2 showed different patterns of DIC utilization. WithN. oculata, P. tricornutum andP. purpureum the pattern of DIC utilization was characterized by an increase of pH and a decrease of DIC but a constant alkalinity in
the cultures aerated with air or CO2-free air, suggesting that bicarbonate utilization was concomitant with an efflux of OH−. Both alkalinity and pH were maintained rather constant in air-grown culture of low-calcifying strain ofE. huxleyi, suggesting that diffusive entry of CO2 could meet the requirement of DIC for its photosynthesis and growth. High-calcifying strain ofE. huxleyi, however, showed a pattern of decrease of alkalinity and DIC but an almost constant pH, indicating that bicarbonate was the
major form of inorganic carbon utilised by this organism and bicarbonate uptake is unlikely to be accompanied by an efflux
of OH−.
The final pH values reached byN. oculata, P. tricornutum andP. purpureum in a closed system were 10.75, 10.60 and 9.85 respectively, showing that bicarbonate utilisation is concomitant with an efflux
of OH−. While the final pH of 8.4 in high-calcifyingE. huxleyi suggests that bicarbonate utilization was not accompanied by an efflux of OH−.
Contribution No. 3557 from the Institue of Oceanology, Chinese Academy of Sciences.
This work was supported by NERC grant GRE3/7853 U. K. and partly supported by Bio-Engineering Center, SSTC 96-C01-05-01. |
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| Keywords: | inorganic carbon Emiliania huxleyi non-calcifying marine microalgae |
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