Articles | Volume 7, issue 9
Biogeosciences, 7, 2915–2923, 2010
https://doi.org/10.5194/bg-7-2915-2010
Biogeosciences, 7, 2915–2923, 2010
https://doi.org/10.5194/bg-7-2915-2010

  24 Sep 2010

24 Sep 2010

CO2-induced seawater acidification affects physiological performance of the marine diatom Phaeodactylum tricornutum

Y. Wu1, K. Gao1, and U. Riebesell2 Y. Wu et al.
  • 1State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
  • 2Leibniz Institute of Marine Sciences (IFM-GEOMAR), Kiel, Germany

Abstract. CO2/pH perturbation experiments were carried out under two different pCO2 levels (39.3 and 101.3 Pa) to evaluate effects of CO2-induced ocean acidification on the marine diatom Phaeodactylum tricornutum. After acclimation (>20 generations) to ambient and elevated CO2 conditions (with corresponding pH values of 8.15 and 7.80, respectively), growth and photosynthetic carbon fixation rates of high CO2 grown cells were enhanced by 5% and 12%, respectively, and dark respiration stimulated by 34% compared to cells grown at ambient CO2. The half saturation constant (Km) for carbon fixation (dissolved inorganic carbon, DIC) increased by 20% under the low pH and high CO2 condition, reflecting a decreased affinity for HCO3 or/and CO2 and down-regulated carbon concentrating mechanism (CCM). In the high CO2 grown cells, the electron transport rate from photosystem II (PSII) was photoinhibited to a greater extent at high levels of photosynthetically active radiation, while non-photochemical quenching was reduced compared to low CO2 grown cells. This was probably due to the down-regulation of CCM, which serves as a sink for excessive energy. The balance between these positive and negative effects on diatom productivity will be a key factor in determining the net effect of rising atmospheric CO2 on ocean primary production.

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