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SOURCE OF INORGANIC CARBON FOR PHOTOSYNTHESIS IN TWO MARINE DINOFLAGELLATES 1
Author(s) -
Dason Jeffrey S.,
Emma Huertas I.,
Colman Brian
Publication year - 2004
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.2004.03123.x
Subject(s) - bicarbonate , photosynthesis , total inorganic carbon , biology , seawater , carbonic anhydrase , environmental chemistry , carbon dioxide , botany , biochemistry , chemistry , ecology , enzyme , endocrinology
Inorganic carbon uptake was investigated in two marine dinoflagellates, Amphidinium carterae Hulburt and Heterocapsa oceanica Stein. Mass spectrometric and potentiometric assays indicated that both species lacked external carbonic anhydrase (CA). The presence of internal CA was demonstrated by potentiometric assay and by the inhibition of photosynthesis upon the addition of 500 μM ethoxyzolamide a membrane‐permeable inhibitor of CA. The capacity for bicarbonate transport was investigated by comparing the calculated rate of spontaneous CO 2 formation at pH 8.2 and 25°C with the rate of photosynthesis after the addition of 100 μM NaHCO 3 . Both species appeared to have a very limited capacity for direct bicarbonate uptake. Monitoring of CO 2 and O 2 fluxes in both species by mass spectrometry demonstrated a rapid uptake of CO 2 on illumination, to concentrations below the CO 2 equilibrium concentration, indicating an effective selective uptake of CO 2 . This dependence of photosynthesis on free CO 2 alone suggests that these species are CO 2 limited in their natural environment because the CO 2 concentration of seawater is very low.