期刊
NEW PHYTOLOGIST
卷 211, 期 1, 页码 126-137出版社
WILEY
DOI: 10.1111/nph.13885
关键词
calcification; CO2-concentrating mechanism; life-cycle stages; membrane-inlet mass spectrometry; ocean acidification; pH; photosynthesis
资金
- German Federal Ministry for Education and Research (BMBF) [031A518C, 03F0655B]
A combined increase in seawater [CO2] and [H+] was recently shown to induce a shift from photosynthetic HCO3- to CO2 uptake in Emiliania huxleyi. This shift occurred within minutes, whereas acclimation to ocean acidification (OA) did not affect the carbon source. To identify the driver of this shift, we exposed low-and high-light acclimated E. huxleyi to a matrix of two levels of dissolved inorganic carbon (1400, 2800 mu mol kg(-1)) and pH (8.15, 7.85) and directly measured cellular O-2, CO2 and HCO3- fluxes under these conditions. Exposure to increased [CO2] had little effect on the photosynthetic fluxes, whereas increased [H+] led to a significant decline in HCO3- uptake. Low-light acclimated cells overcompensated for the inhibition of HCO3- uptake by increasing CO2 uptake. High-light acclimated cells, relying on higher proportions of HCO3- uptake, could not increase CO2 uptake and photosynthetic O-2 evolution consequently became carbon-limited. These regulations indicate that OA responses in photosynthesis are caused by [H+] rather than by [CO2]. The impaired HCO3- uptake also provides a mechanistic explanation for lowered calcification under OA. Moreover, it explains the OA-dependent decrease in photosynthesis observed in high-light grown phytoplankton.
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