CO 2 -induced seawater acidification affects physiological performance of the marine diatom Phaeodactylum tricornutum

• Published in: Biogeosciences
• Main Authors: U. Riebesell, K. Gao, Y. Wu
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2010
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Ocean acidification
• Online Access: https://doi.org/10.5194/bg-7-2915-2010; https://doaj.org/article/0342b05e466e4da48ae2c503faf7068f

CO 2 /pH perturbation experiments were carried out under two different p CO 2 levels (39.3 and 101.3 Pa) to evaluate effects of CO 2 -induced ocean acidification on the marine diatom Phaeodactylum tricornutum. After acclimation (>20 generations) to ambient and elevated CO 2 conditions (with corresponding pH values of 8.15 and 7.80, respectively), growth and photosynthetic carbon fixation rates of high CO 2 grown cells were enhanced by 5% and 12%, respectively, and dark respiration stimulated by 34% compared to cells grown at ambient CO 2 . The half saturation constant ( K m ) for carbon fixation (dissolved inorganic carbon, DIC) increased by 20% under the low pH and high CO 2 condition, reflecting a decreased affinity for HCO 3 – or/and CO 2 and down-regulated carbon concentrating mechanism (CCM). In the high CO 2 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 CO 2 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 CO 2 on ocean primary production.