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EFFECTS OF CO 2 ENRICHMENT ON THE BLOOM‐FORMING CYANOBACTERIUM MICROCYSTIS AERUGINOSA (CYANOPHYCEAE): PHYSIOLOGICAL RESPONSES AND RELATIONSHIPS WITH THE AVAILABILITY OF DISSOLVED INORGANIC CARBON 1
Author(s) -
Qiu Baosheng,
Gao Kunshan
Publication year - 2002
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 - 10.1046/j.1529-8817.2002.01180.x
Subject(s) - photosynthesis , dissolved organic carbon , microcystis aeruginosa , biology , aeration , total inorganic carbon , carbon dioxide , bloom , botany , cyanobacteria , ecology , bacteria , genetics
Microcystis aeruginosa Kütz. 7820 was cultured at 350 and 700 μL·L − 1 CO 2 to assess the impacts of doubled atmospheric CO 2 concentration on this bloom‐forming cyanobacterium. Doubling of CO 2 concentration in the airflow enhanced its growth by 52%–77%, with pH values decreased and dissolved inorganic carbon (DIC) increased in the medium. Photosynthetic efficiencies and dark respiratory rates expressed per unit chl a tended to increase with the doubling of CO 2 . However, saturating irradiances for photosynthesis and light‐saturated photosynthetic rates normalized to cell number tended to decrease with the increase of DIC in the medium. Doubling of CO 2 concentration in the airflow had less effect on DIC‐saturated photosynthetic rates and apparent photosynthetic affinities for DIC. In the exponential phase, CO 2 and HCO 3 − levels in the medium were higher than those required to saturate photosynthesis. Cultures with surface aeration were DIC limited in the stationary phase. The rate of CO 2 dissolution into the liquid increased proportionally when CO 2 in air was raised from 350 to 700 μL·L − 1 , thus increasing the availability of DIC in the medium and enhancing the rate of photosynthesis. Doubled CO 2 could enhance CO 2 dissolution, lower pH values, and influence the ionization fractions of various DIC species even when the photosynthesis was not DIC limited. Consequently, HCO 3 − concentrations in cultures were significantly higher than in controls, and the photosynthetic energy cost for the operation of CO 2 concentrating mechanism might decrease.