In order to learn the ways and possible utilization mechanisms of dissolved inorganic carbon (DIC) in marine phytoplankton species under carbon replete or limited conditions, the activity of extracellular carbonic anhydrase (CA) was assayed in different pH, CO2 and DIC concentrations. Extracellular CA in Amphidinium carterae and Prorocentrum minimum was detected under carbon replete conditions, while in Melosira sp., Phaeodactylum tricornutum, Skeletonema costatum, Thalassiosira rotula, Emiliania huxleyi and Pleurochrysis carterae, CA activity was assayed under conditions of carbon limitation. No CA activity was found even under carbon limited conditions in Chaetoceros compressus, Glenodinium foliaceum, Coccolithus pelagicus, Gephrocapsa oceanica and Heterosigma akashiwo. In species without extracellular CA activity, the direct HCO3- uptake was investigated using a pH drift technique and the anion exchange inhibitor 4′4′diisothiocyanatostilbene 2,2 disulfonic acid (DIDS) in a closed system. The result showed that direct HCO3- transport might occur by an anion exchange mechanism in species Coc. pelagicus and G. oceanica. Of the 13 species investigated, only H. akashiwo did not have the potential for direct uptake or extracellular CA catalyzed HCO3- utilization.
海洋浮游藻类无机碳利用机理的研究
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