CO₂-driven seawater acidification increases photochemical stress in a green alga
2012
Liu, Yuting | Xu, Juntian | Gao, Kunshan
Liu Y., Xu J. and Gao K. 2012. CO₂-driven seawater acidification increases photochemical stress in a green alga. Phycologia 51: 562–566. DOI: 10.2216/11-65.1 Increased CO₂ and associated acidification in seawater, known as ocean acidification, decreases calcification of most marine calcifying organisms. However, there is little information available on how marine macroalgae would respond to the chemical changes caused by seawater acidification. We hypothesized that down-regulation of bicarbonate acquisition by algae under increased acidity and CO₂ levels would lower the threshold above which photosynthetically active radiation (PAR) becomes excessive. Juveniles of Ulva prolifera derived from zoospores were grown at ambient (390 µatm) and elevated (1000 µatm) CO₂ concentrations for 80 days before the hypothesis was tested. Here, the CO₂-induced seawater acidification increased the quantum yield under low levels of light, but induced higher nonphotochemical quenching under high light. At the same time, the PAR level at which photosynthesis became saturated was decreased and the photosynthetic affinity for CO₂ or inorganic carbon decreased in the high-CO₂ grown plants. These findings indicated that ocean acidification, as an environmental stressor, can reduce the threshold above which PAR becomes excessive.
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