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www.biogeosciences-discuss.net/7/3855/2010/
doi:10.5194/bgd-7-3855-2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
CO2-induced seawater acidification affects physiological performance of the marine diatom Phaeodactylum tricornutum
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 K1/2 (dissolved inorganic carbon, DIC) for carbon fixation increased by 20% under the low pH and high CO2 condition, reflecting a decreased photosynthetic 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. Increasing seawater pCO2 and decreasing pH associated with atmospheric CO2 rise may enhance diatom growth, down-regulate their CCM, and enhanced their photo-inhibition and dark respiration. 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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Notice on Discussion StatusCitation: Wu, Y., Gao, K., and Riebesell, U.: CO2-induced seawater acidification affects physiological performance of the marine diatom Phaeodactylum tricornutum, Biogeosciences Discuss., 7, 3855-3878, doi:10.5194/bgd-7-3855-2010, 2010. Bibtex EndNote Reference Manager XML
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